1 . $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.2 2006/04/04 14:03:49 ph10 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.
8 . /////////////////////////////////////////////////////////////////////////////
15 . /////////////////////////////////////////////////////////////////////////////
16 . These definitions set some parameters and save some typing. Remember that
17 . the <bookinfo> element must also be updated for each new edition.
18 . /////////////////////////////////////////////////////////////////////////////
20 .set ACL "access control lists (ACLs)"
21 .set previousversion "4.60"
25 . /////////////////////////////////////////////////////////////////////////////
26 . Additional xfpt markup used by this document, over and above the default
27 . provided in the xfpt library.
28 . /////////////////////////////////////////////////////////////////////////////
30 . --- Override the &$ flag to automatically insert a $ with the variable name
32 .flag &$ $& "<varname>$" "</varname>"
34 . --- Short flags for daggers in option headings. They will always be inside
35 . --- an italic string, but we want the daggers to be roman.
37 .flag &!! "</emphasis>†<emphasis>"
38 .flag &!? "</emphasis>‡<emphasis>"
40 . --- A macro for an Exim option definition heading, generating a one-line
41 . --- table with four columns.
45 .itable all 0 0 4 8* left 5* center 5* center 6* right
46 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
50 . --- A macro for the common 2-column tables. The width of the first column
51 . --- is suitable for the many tables at the start of the main options chapter;
52 . --- the small number of other 2-column tables override it.
54 .macro table2 190pt 260pt
55 .itable none 0 0 2 $1 left $2 left
58 . --- Macros for the concept and option index entries. For a "range" style of
59 . --- entry, use .scindex for the start and .ecindex for the end. The first
60 . --- argument of .scindex and the only argument of .ecindex must be the ID
61 . --- that ties them together.
64 &<indexterm role="concept">&
65 &<primary>&$1&</primary>&
67 &<secondary>&$2&</secondary>&
73 &<indexterm role="concept" id="$1" class="startofrange">&
74 &<primary>&$2&</primary>&
76 &<secondary>&$3&</secondary>&
82 &<indexterm role="concept" startref="$1" class="endofrange"/>&
86 &<indexterm role="option">&
87 &<primary>&$1&</primary>&
89 &<secondary>&$2&</secondary>&
95 .echo "** Don't use .index; use .cindex or .oindex"
97 . ////////////////////////////////////////////////////////////////////////////
100 . ////////////////////////////////////////////////////////////////////////////
101 . The <bookinfo> element is removed from the XML before processing for Ascii
103 . ////////////////////////////////////////////////////////////////////////////
107 <title>Specification of the Exim Mail Transfer Agent</title>
108 <titleabbrev>The Exim MTA</titleabbrev>
109 <date>22 March 2006</date>
110 <author><firstname>Philip</firstname><surname>Hazel</surname></author>
111 <authorinitials>PH</authorinitials>
112 <affiliation><orgname>University of Cambridge Computing Service</orgname></affiliation>
113 <address>New Museums Site, Pembroke Street, Cambridge CB2 3QH, England</address>
114 <revhistory><revision>
115 <revnumber>4.61</revnumber>
116 <date>22 March 2006</date>
117 <authorinitials>PH</authorinitials>
118 </revision></revhistory>
119 <copyright><year>2006</year><holder>University of Cambridge</holder></copyright>
124 . /////////////////////////////////////////////////////////////////////////////
125 . This chunk of literal XML implements index entries of the form "x, see y" and
126 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
127 . at the top level, so we have to put the .chapter directive first.
128 . /////////////////////////////////////////////////////////////////////////////
130 .chapter "Introduction"
133 <indexterm role="concept">
134 <primary>$1, $2, etc.</primary>
135 <see><emphasis>numerical variables</emphasis></see>
137 <indexterm role="concept">
138 <primary>address</primary>
139 <secondary>rewriting</secondary>
140 <see><emphasis>rewriting</emphasis></see>
142 <indexterm role="concept">
143 <primary>Bounce Address Tag Validation</primary>
144 <see><emphasis>BATV</emphasis></see>
146 <indexterm role="concept">
147 <primary>Client SMTP Authorization</primary>
148 <see><emphasis>CSA</emphasis></see>
150 <indexterm role="concept">
151 <primary>CR character</primary>
152 <see><emphasis>carriage return</emphasis></see>
154 <indexterm role="concept">
155 <primary>CRL</primary>
156 <see><emphasis>certificate revocation list</emphasis></see>
158 <indexterm role="concept">
159 <primary>delivery</primary>
160 <secondary>failure report</secondary>
161 <see><emphasis>bounce message</emphasis></see>
163 <indexterm role="concept">
164 <primary>dialup</primary>
165 <see><emphasis>intermittently connected hosts</emphasis></see>
167 <indexterm role="concept">
168 <primary>exiscan</primary>
169 <see><emphasis>content scanning</emphasis></see>
171 <indexterm role="concept">
172 <primary>failover</primary>
173 <see><emphasis>fallback</emphasis></see>
175 <indexterm role="concept">
176 <primary>fallover</primary>
177 <see><emphasis>fallback</emphasis></see>
179 <indexterm role="concept">
180 <primary>filter</primary>
181 <secondary>Sieve</secondary>
182 <see><emphasis>Sieve filter</emphasis></see>
184 <indexterm role="concept">
185 <primary>ident</primary>
186 <see><emphasis>RFC 1413</emphasis></see>
188 <indexterm role="concept">
189 <primary>LF character</primary>
190 <see><emphasis>linefeed</emphasis></see>
192 <indexterm role="concept">
193 <primary>maximum</primary>
194 <see><emphasis>limit</emphasis></see>
196 <indexterm role="concept">
197 <primary>monitor</primary>
198 <see><emphasis>Exim monitor</emphasis></see>
200 <indexterm role="concept">
201 <primary>no_<emphasis>xxx</emphasis></primary>
202 <see>entry for xxx</see>
204 <indexterm role="concept">
205 <primary>NUL</primary>
206 <see><emphasis>binary zero</emphasis></see>
208 <indexterm role="concept">
209 <primary>passwd file</primary>
210 <see><emphasis>/etc/passwd</emphasis></see>
212 <indexterm role="concept">
213 <primary>process id</primary>
214 <see><emphasis>pid</emphasis></see>
216 <indexterm role="concept">
217 <primary>RBL</primary>
218 <see><emphasis>DNS list</emphasis></see>
220 <indexterm role="concept">
221 <primary>redirection</primary>
222 <see><emphasis>address redirection</emphasis></see>
224 <indexterm role="concept">
225 <primary>return path</primary>
226 <seealso><emphasis>envelope sender</emphasis></seealso>
228 <indexterm role="concept">
229 <primary>scanning</primary>
230 <see><emphasis>content scanning</emphasis></see>
232 <indexterm role="concept">
233 <primary>SSL</primary>
234 <see><emphasis>TLS</emphasis></see>
236 <indexterm role="concept">
237 <primary>string</primary>
238 <secondary>expansion</secondary>
239 <see><emphasis>expansion</emphasis></see>
241 <indexterm role="concept">
242 <primary>top bit</primary>
243 <see><emphasis>8-bit characters</emphasis></see>
245 <indexterm role="concept">
246 <primary>variables</primary>
247 <see><emphasis>expansion, variables</emphasis></see>
249 <indexterm role="concept">
250 <primary>zero, binary</primary>
251 <see><emphasis>binary zero</emphasis></see>
257 . /////////////////////////////////////////////////////////////////////////////
258 . This is the real start of the first chapter. See the comment above as to why
259 . we can't have the .chapter line here.
260 . chapter "Introduction"
261 . /////////////////////////////////////////////////////////////////////////////
263 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
264 Unix-like operating systems. It was designed on the assumption that it would be
265 run on hosts that are permanently connected to the Internet. However, it can be
266 used on intermittently connected hosts with suitable configuration adjustments.
268 Configuration files currently exist for the following operating systems: AIX,
269 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
270 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
271 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
272 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
273 Some of these operating systems are no longer current and cannot easily be
274 tested, so the configuration files may no longer work in practice.
276 There are also configuration files for compiling Exim in the Cygwin environment
277 that can be installed on systems running Windows. However, this document does
278 not contain any information about running Exim in the Cygwin environment.
280 The terms and conditions for the use and distribution of Exim are contained in
281 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
282 Public Licence, a copy of which may be found in the file &_LICENCE_&.
284 The use, supply or promotion of Exim for the purpose of sending bulk,
285 unsolicited electronic mail is incompatible with the basic aims of the program,
286 which revolve around the free provision of a service that enhances the quality
287 of personal communications. The author of Exim regards indiscriminate
288 mass-mailing as an antisocial, irresponsible abuse of the Internet.
290 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
291 experience of running and working on the Smail 3 code, I could never have
292 contemplated starting to write a new MTA. Many of the ideas and user interfaces
293 were originally taken from Smail 3, though the actual code of Exim is entirely
294 new, and has developed far beyond the initial concept.
296 Many people, both in Cambridge and around the world, have contributed to the
297 development and the testing of Exim, and to porting it to various operating
298 systems. I am grateful to them all. The distribution now contains a file called
299 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
303 .section "Exim documentation"
305 .cindex "documentation"
306 This edition of the Exim specification applies to version &version; of Exim.
307 Substantive changes from the &previousversion; edition are marked in some
308 renditions of the document; this paragraph is so marked if the rendition is
309 capable of showing a change indicator.
312 This document is very much a reference manual; it is not a tutorial. The reader
313 is expected to have some familiarity with the SMTP mail transfer protocol and
314 with general Unix system administration. Although there are some discussions
315 and examples in places, the information is mostly organized in a way that makes
316 it easy to look up, rather than in a natural order for sequential reading.
317 Furthermore, the manual aims to cover every aspect of Exim in detail, including
318 a number of rarely-used, special-purpose features that are unlikely to be of
321 .cindex "books about Exim"
322 An &"easier"& discussion of Exim which provides more in-depth explanatory,
323 introductory, and tutorial material can be found in a book entitled &'The Exim
324 SMTP Mail Server'&, published by UIT Cambridge
325 (&url(http://www.uit.co.uk/exim-book/)).
327 This book also contains a chapter that gives a general introduction to SMTP and
328 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
329 with the latest release of Exim. (Note that the earlier book about Exim,
330 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
332 .cindex "Debian" "information sources"
333 If you are using a Debian distribution of Exim, you will find information about
334 Debian-specific features in the file
336 &_/usr/share/doc/exim4-base/README.Debian_&
338 The command &(man update-exim.conf)& is another source of Debian-specific
341 .cindex "&_doc/NewStuff_&"
342 .cindex "&_doc/ChangeLog_&"
344 As the program develops, there may be features in newer versions that have not
345 yet made it into this document, which is updated only when the most significant
346 digit of the fractional part of the version number changes. Specifications of
347 new features that are not yet in this manual are placed in the file
348 &_doc/NewStuff_& in the Exim distribution.
350 Some features may be classified as &"experimental"&. These may change
351 incompatibly while they are developing, or even be withdrawn. For this reason,
352 they are not documented in this manual. Information about experimental features
353 can be found in the file &_doc/experimental.txt_&.
355 All changes to the program (whether new features, bug fixes, or other kinds of
356 change) are noted briefly in the file called &_doc/ChangeLog_&.
358 .cindex "&_doc/spec.txt_&"
359 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
360 that it can easily be searched with a text editor. Other files in the &_doc_&
364 .row &_OptionLists.txt_& "list of all options in alphabetical order"
365 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
366 .row &_exim.8_& "a man page of Exim's command line options"
367 .row &_experimental.txt_& "documentation of experimental features"
368 .row &_filter.txt_& "specification of the filter language"
369 .row &_pcrepattern.txt_& "specification of PCRE regular expressions"
370 .row &_pcretest.txt_& "specification of the PCRE testing program"
371 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
372 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
375 The main specification and the specification of the filtering language are also
376 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
377 &<<SECTavail>>& below tells you how to get hold of these.
381 .section "FTP and web sites"
384 The primary site for Exim source distributions is currently the University of
385 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
386 distribution'& below. In addition, there is a web site and an FTP site at
387 &%exim.org%&. These are now also hosted at the University of Cambridge. The
388 &%exim.org%& site was previously hosted for a number of years by Energis
389 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
393 As well as Exim distribution tar files, the Exim web site contains a number of
394 differently formatted versions of the documentation, including the FAQ in both
395 text and HTML formats. The HTML version comes with a keyword-in-context index.
396 A recent addition to the online information is the Exim wiki
397 (&url(http://www.exim.org/eximwiki/)). We hope that this will make it easier
398 for Exim users to contribute examples, tips, and know-how for the benefit of
403 .section "Mailing lists"
404 .cindex "mailing lists" "for Exim users"
405 The following are the three main Exim mailing lists:
408 .row &'exim-users@exim.org'& "general discussion list"
409 .row &'exim-dev@exim.org'& "discussion of bugs, enhancements, etc."
410 .row &'exim-announce@exim.org'& "moderated, low volume announcements list"
413 You can subscribe to these lists, change your existing subscriptions, and view
414 or search the archives via the mailing lists link on the Exim home page.
415 .cindex "Debian" "mailing list for"
416 If you are using a Debian distribution of Exim, you may wish to subscribe to
417 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&.
419 .section "Exim training"
420 .cindex "training courses"
421 From time to time (approximately annually at the time of writing), training
422 courses are run by the author of Exim in Cambridge, UK. Details of any
423 forthcoming courses can be found on the web site
424 &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
427 .section "Bug reports"
428 .cindex "bug reports"
429 .cindex "reporting bugs"
430 Reports of obvious bugs should be emailed to &'bugs@exim.org'&. However, if you
431 are unsure whether some behaviour is a bug or not, the best thing to do is to
432 post a message to the &'exim-dev'& mailing list and have it discussed.
436 .section "Where to find the Exim distribution" "SECTavail"
438 .cindex "distribution" "ftp site"
439 The master ftp site for the Exim distribution is
441 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
445 &*ftp://ftp.exim.org/pub/exim*&
447 The file references that follow are relative to the &_exim_& directories at
448 these sites. There are now quite a number of independent mirror sites around
449 the world. Those that I know about are listed in the file called &_Mirrors_&.
451 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
452 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
453 distributions), and &_Testing_& for testing versions. In the &_exim4_&
454 subdirectory, the current release can always be found in files called
457 &_exim-n.nn.tar.bz2_&
459 where &'n.nn'& is the highest such version number in the directory. The two
460 files contain identical data; the only difference is the type of compression.
461 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
463 .cindex "distribution" "signing details"
464 .cindex "distribution" "public key"
465 .cindex "public key for signed distribution"
466 The distributions are currently signed with Philip Hazel's GPG key. The
467 corresponding public key is available from a number of keyservers, and there is
468 also a copy in the file &_Public-Key_&. The signatures for the tar bundles are
471 &_exim-n.nn.tar.gz.sig_&
472 &_exim-n.nn.tar.bz2.sig_&
474 For each released version, the log of changes is made separately available in a
475 separate file in the directory &_ChangeLogs_& so that it is possible to
476 find out what has changed without having to download the entire distribution.
478 .cindex "documentation" "available formats"
479 The main distribution contains ASCII versions of this specification and other
480 documentation; other formats of the documents are available in separate files
481 inside the &_exim4_& directory of the FTP site:
483 &_exim-html-n.nn.tar.gz_&
484 &_exim-pdf-n.nn.tar.gz_&
485 &_exim-postscript-n.nn.tar.gz_&
486 &_exim-texinfo-n.nn.tar.gz_&
488 These tar files contain only the &_doc_& directory, not the complete
489 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
491 The FAQ is available for downloading in two different formats in these files:
494 &_exim4/FAQ.html.tar.gz_&
496 The first of these is a single ASCII file that can be searched with a text
497 editor. The second is a directory of HTML files, normally accessed by starting
498 at &_index.html_&. The HTML version of the FAQ (which is also included in the
499 HTML documentation tarbundle) includes a keyword-in-context index, which is
500 often the most convenient way of finding your way around.
505 A wish list is maintained, containing ideas for new features that have been
506 submitted. From time to time the file is exported to the ftp site into the file
507 &_exim4/WishList_&. Items are removed from the list if they get implemented.
511 .section "Contributed material"
512 .cindex "contributed material"
513 At the ftp site, there is a directory called &_Contrib_& that contains
514 miscellaneous files contributed to the Exim community by Exim users. There is
515 also a collection of contributed configuration examples in
516 &_exim4/config.samples.tar.gz_&. These samples are referenced from the FAQ.
520 .section "Limitations"
522 .cindex "limitations of Exim"
523 .cindex "bang paths" "not handled by Exim"
524 Exim is designed for use as an Internet MTA, and therefore handles addresses in
525 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
526 simple two-component bang paths can be converted by a straightforward rewriting
527 configuration. This restriction does not prevent Exim from being interfaced to
528 UUCP as a transport mechanism, provided that domain addresses are used.
530 .cindex "domainless addresses"
531 .cindex "address" "without domain"
532 Exim insists that every address it handles has a domain attached. For incoming
533 local messages, domainless addresses are automatically qualified with a
534 configured domain value. Configuration options specify from which remote
535 systems unqualified addresses are acceptable. These are then qualified on
538 .cindex "transport" "external"
539 .cindex "external transports"
540 The only external transport mechanisms that are currently implemented are SMTP
541 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
542 transport is available, and there are facilities for writing messages to files
543 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
544 to send messages to other transport mechanisms such as UUCP, provided they can
545 handle domain-style addresses. Batched SMTP input is also catered for.
547 Exim is not designed for storing mail for dial-in hosts. When the volumes of
548 such mail are large, it is better to get the messages &"delivered"& into files
549 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
552 Although Exim does have basic facilities for scanning incoming messages, these
553 are not comprehensive enough to do full virus or spam scanning. Such operations
554 are best carried out using additional specialized software packages. If you
555 compile Exim with the content-scanning extension, straightforward interfaces to
556 a number of common scanners are provided.
560 .section "Run time configuration"
561 Exim's run time configuration is held in a single text file that is divided
562 into a number of sections. The entries in this file consist of keywords and
563 values, in the style of Smail 3 configuration files. A default configuration
564 file which is suitable for simple online installations is provided in the
565 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
568 .section "Calling interface"
569 .cindex "Sendmail compatibility" "command line interface"
570 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
571 can be a straight replacement for &_/usr/lib/sendmail_& or
572 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
573 about Sendmail in order to run Exim. For actions other than sending messages,
574 Sendmail-compatible options also exist, but those that produce output (for
575 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
576 format. There are also some additional options that are compatible with Smail
577 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
578 documents all Exim's command line options. This information is automatically
579 made into the man page that forms part of the Exim distribution.
581 Control of messages on the queue can be done via certain privileged command
582 line options. There is also an optional monitor program called &'eximon'&,
583 which displays current information in an X window, and which contains a menu
584 interface to Exim's command line administration options.
588 .section "Terminology"
589 .cindex "terminology definitions"
590 .cindex "body of message" "definition of"
591 The &'body'& of a message is the actual data that the sender wants to transmit.
592 It is the last part of a message, and is separated from the &'header'& (see
593 below) by a blank line.
595 .cindex "bounce message" "definition of"
596 When a message cannot be delivered, it is normally returned to the sender in a
597 delivery failure message or a &"non-delivery report"& (NDR). The term
598 &'bounce'& is commonly used for this action, and the error reports are often
599 called &'bounce messages'&. This is a convenient shorthand for &"delivery
600 failure error report"&. Such messages have an empty sender address in the
601 message's &'envelope'& (see below) to ensure that they cannot themselves give
602 rise to further bounce messages.
604 The term &'default'& appears frequently in this manual. It is used to qualify a
605 value which is used in the absence of any setting in the configuration. It may
606 also qualify an action which is taken unless a configuration setting specifies
609 The term &'defer'& is used when the delivery of a message to a specific
610 destination cannot immediately take place for some reason (a remote host may be
611 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
614 The word &'domain'& is sometimes used to mean all but the first component of a
615 host's name. It is &'not'& used in that sense here, where it normally refers to
616 the part of an email address following the @ sign.
618 .cindex "envelope" "definition of"
619 .cindex "sender" "definition of"
620 A message in transit has an associated &'envelope'&, as well as a header and a
621 body. The envelope contains a sender address (to which bounce messages should
622 be delivered), and any number of recipient addresses. References to the
623 sender or the recipients of a message usually mean the addresses in the
624 envelope. An MTA uses these addresses for delivery, and for returning bounce
625 messages, not the addresses that appear in the header lines.
627 .cindex "message header" "definition of"
628 .cindex "header section" "definition of"
629 The &'header'& of a message is the first part of a message's text, consisting
630 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
631 &'Subject:'&, etc. Long header lines can be split over several text lines by
632 indenting the continuations. The header is separated from the body by a blank
635 .cindex "local part" "definition of"
636 .cindex "domain" "definition of"
637 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
638 part of an email address that precedes the @ sign. The part that follows the
639 @ sign is called the &'domain'& or &'mail domain'&.
641 .cindex "local delivery" "definition of"
642 .cindex "remote delivery" "definition of"
643 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
644 delivery to a file or a pipe on the local host from delivery by SMTP over
645 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
646 host it is running on are &'remote'&.
648 .cindex "return path" "definition of"
649 &'Return path'& is another name that is used for the sender address in a
652 .cindex "queue" "definition of"
653 The term &'queue'& is used to refer to the set of messages awaiting delivery,
654 because this term is in widespread use in the context of MTAs. However, in
655 Exim's case the reality is more like a pool than a queue, because there is
656 normally no ordering of waiting messages.
658 .cindex "queue runner" "definition of"
659 The term &'queue runner'& is used to describe a process that scans the queue
660 and attempts to deliver those messages whose retry times have come. This term
661 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
662 the waiting messages are normally processed in an unpredictable order.
664 .cindex "spool directory" "definition of"
665 The term &'spool directory'& is used for a directory in which Exim keeps the
666 messages on its queue &-- that is, those that it is in the process of
667 delivering. This should not be confused with the directory in which local
668 mailboxes are stored, which is called a &"spool directory"& by some people. In
669 the Exim documentation, &"spool"& is always used in the first sense.
676 . ////////////////////////////////////////////////////////////////////////////
677 . ////////////////////////////////////////////////////////////////////////////
679 .chapter "Incorporated code"
680 .cindex "incorporated code"
681 .cindex "regular expressions" "library"
683 A number of pieces of external code are included in the Exim distribution.
686 Regular expressions are supported in the main Exim program and in the Exim
687 monitor using the freely-distributable PCRE library, copyright ©
688 University of Cambridge. The source is distributed in the directory
689 &_src/pcre_&. However, this is a cut-down version of PCRE. If you want to use
690 the PCRE library in other programs, you should obtain and install the full
691 version from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
693 .cindex "cdb" "acknowledgement"
694 Support for the cdb (Constant DataBase) lookup method is provided by code
695 contributed by Nigel Metheringham of (at the time he contributed it) Planet
696 Online Ltd. The implementation is completely contained within the code of Exim.
697 It does not link against an external cdb library. The code contains the
698 following statements:
701 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
703 This program is free software; you can redistribute it and/or modify it under
704 the terms of the GNU General Public License as published by the Free Software
705 Foundation; either version 2 of the License, or (at your option) any later
708 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
709 the spec and sample code for cdb can be obtained from
710 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows some
711 code from Dan Bernstein's implementation (which has no license restrictions
715 .cindex "SPA authentication"
716 .cindex "Samba project"
717 .cindex "Microsoft Secure Password Authentication"
718 Client support for Microsoft's &'Secure Password Authentication'& is provided
719 by code contributed by Marc Prud'hommeaux. Server support was contributed by
720 Tom Kistner. This includes code taken from the Samba project, which is released
724 .cindex "&'pwcheck'& daemon"
725 .cindex "&'pwauthd'& daemon"
726 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
727 by code taken from the Cyrus-SASL library and adapted by Alexander S.
728 Sabourenkov. The permission notice appears below, in accordance with the
729 conditions expressed therein.
732 Copyright © 2001 Carnegie Mellon University. All rights reserved.
734 Redistribution and use in source and binary forms, with or without
735 modification, are permitted provided that the following conditions
739 Redistributions of source code must retain the above copyright
740 notice, this list of conditions and the following disclaimer.
742 Redistributions in binary form must reproduce the above copyright
743 notice, this list of conditions and the following disclaimer in
744 the documentation and/or other materials provided with the
747 The name &"Carnegie Mellon University"& must not be used to
748 endorse or promote products derived from this software without
749 prior written permission. For permission or any other legal
750 details, please contact
752 Office of Technology Transfer
753 Carnegie Mellon University
755 Pittsburgh, PA 15213-3890
756 (412) 268-4387, fax: (412) 268-7395
757 tech-transfer@andrew.cmu.edu
760 Redistributions of any form whatsoever must retain the following
763 &"This product includes software developed by Computing Services
764 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
766 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
767 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
768 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
769 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
770 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
771 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
772 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
777 .cindex "Exim monitor" "acknowledgement"
780 The Exim Monitor program, which is an X-Window application, includes
781 modified versions of the Athena StripChart and TextPop widgets.
782 This code is copyright by DEC and MIT, and their permission notice appears
783 below, in accordance with the conditions expressed therein.
786 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
787 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
791 Permission to use, copy, modify, and distribute this software and its
792 documentation for any purpose and without fee is hereby granted,
793 provided that the above copyright notice appear in all copies and that
794 both that copyright notice and this permission notice appear in
795 supporting documentation, and that the names of Digital or MIT not be
796 used in advertising or publicity pertaining to distribution of the
797 software without specific, written prior permission.
799 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
800 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
801 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
802 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
803 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
804 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
809 Many people have contributed code fragments, some large, some small, that were
810 not covered by any specific licence requirements. It is assumed that the
811 contributors are happy to see their code incoporated into Exim under the GPL.
818 . ////////////////////////////////////////////////////////////////////////////
819 . ////////////////////////////////////////////////////////////////////////////
821 .chapter "How Exim receives and delivers mail" "" &&&
822 "Receiving and delivering mail"
825 .section "Overall philosophy"
826 .cindex "design philosophy"
827 Exim is designed to work efficiently on systems that are permanently connected
828 to the Internet and are handling a general mix of mail. In such circumstances,
829 most messages can be delivered immediately. Consequently, Exim does not
830 maintain independent queues of messages for specific domains or hosts, though
831 it does try to send several messages in a single SMTP connection after a host
832 has been down, and it also maintains per-host retry information.
835 .section "Policy control"
836 .cindex "policy control" "overview"
837 Policy controls are now an important feature of MTAs that are connected to the
838 Internet. Perhaps their most important job is to stop MTAs being abused as
839 &"open relays"& by misguided individuals who send out vast amounts of
840 unsolicited junk, and want to disguise its source. Exim provides flexible
841 facilities for specifying policy controls on incoming mail:
844 .cindex "&ACL;" "introduction"
845 Exim 4 (unlike previous versions of Exim) implements policy controls on
846 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
847 series of statements that may either grant or deny access. ACLs can be used at
848 several places in the SMTP dialogue while receiving a message from a remote
849 host. However, the most common places are after each RCPT command, and at the
850 very end of the message. The sysadmin can specify conditions for accepting or
851 rejecting individual recipients or the entire message, respectively, at these
852 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
855 An ACL is also available for locally generated, non-SMTP messages. In this
856 case, the only available actions are to accept or deny the entire message.
858 When Exim is compiled with the content-scanning extension, facilities are
859 provided in the ACL mechanism for passing the message to external virus and/or
860 spam scanning software. The result of such a scan is passed back to the ACL,
861 which can then use it to decide what to do with the message.
863 When a message has been received, either from a remote host or from the local
864 host, but before the final acknowledgement has been sent, a locally supplied C
865 function called &[local_scan()]& can be run to inspect the message and decide
866 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
867 is accepted, the list of recipients can be modified by the function.
869 Using the &[local_scan()]& mechanism is another way of calling external scanner
870 software. The &%SA-Exim%& add-on package works this way. It does not require
871 Exim to be compiled with the content-scanning extension.
873 After a message has been accepted, a further checking mechanism is available in
874 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
875 runs at the start of every delivery process.
880 .section "User filters"
881 .cindex "filter" "introduction"
882 .cindex "Sieve filter"
883 In a conventional Exim configuration, users are able to run private filters by
884 setting up appropriate &_.forward_& files in their home directories. See
885 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
886 configuration needed to support this, and the separate document entitled
887 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
888 of filtering are available:
891 Sieve filters are written in the standard filtering language that is defined
894 Exim filters are written in a syntax that is unique to Exim, but which is more
895 powerful than Sieve, which it pre-dates.
898 User filters are run as part of the routing process, described below.
902 .section "Message identification" "SECTmessiden"
903 .cindex "message ids" "details of format"
904 .cindex "format" "of message id"
905 .cindex "id of message"
910 Every message handled by Exim is given a &'message id'& which is sixteen
911 characters long. It is divided into three parts, separated by hyphens, for
912 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
913 normally encoding numbers in base 62. However, in the Darwin operating
914 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
915 (avoiding the use of lower case letters) is used instead, because the message
916 id is used to construct file names, and the names of files in those systems are
917 not always case-sensitive.
919 .cindex "pid (process id)" "re-use of"
920 The detail of the contents of the message id have changed as Exim has evolved.
921 Earlier versions relied on the operating system not re-using a process id (pid)
922 within one second. On modern operating systems, this assumption can no longer
923 be made, so the algorithm had to be changed. To retain backward compatibility,
924 the format of the message id was retained, which is why the following rules are
928 The first six characters of the message id are the time at which the message
929 started to be received, to a granularity of one second. That is, this field
930 contains the number of seconds since the start of the epoch (the normal Unix
931 way of representing the date and time of day).
933 After the first hyphen, the next six characters are the id of the process that
934 received the message.
936 There are two different possibilities for the final two characters:
938 .cindex "&%localhost_number%&"
939 If &%localhost_number%& is not set, this value is the fractional part of the
940 time of reception, normally in units of 1/2000 of a second, but for systems
941 that must use base 36 instead of base 62 (because of case-insensitive file
942 systems), the units are 1/1000 of a second.
944 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
945 the fractional part of the time, which in this case is in units of 1/200
950 After a message has been received, Exim waits for the clock to tick at the
951 appropriate resolution before proceeding, so that if another message is
952 received by the same process, or by another process with the same (re-used)
953 pid, it is guaranteed that the time will be different. In most cases, the clock
954 will already have ticked while the message was being received.
957 .section "Receiving mail"
958 .cindex "receiving mail"
959 .cindex "message" "reception"
960 The only way Exim can receive mail from another host is using SMTP over
961 TCP/IP, in which case the sender and recipient addresses are transferred using
962 SMTP commands. However, from a locally running process (such as a user's MUA),
963 there are several possibilities:
966 If the process runs Exim with the &%-bm%& option, the message is read
967 non-interactively (usually via a pipe), with the recipients taken from the
968 command line, or from the body of the message if &%-t%& is also used.
970 If the process runs Exim with the &%-bS%& option, the message is also read
971 non-interactively, but in this case the recipients are listed at the start of
972 the message in a series of SMTP RCPT commands, terminated by a DATA
973 command. This is so-called &"batch SMTP"& format,
974 but it isn't really SMTP. The SMTP commands are just another way of passing
975 envelope addresses in a non-interactive submission.
977 If the process runs Exim with the &%-bs%& option, the message is read
978 interactively, using the SMTP protocol. A two-way pipe is normally used for
979 passing data between the local process and the Exim process.
980 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
981 example, the ACLs for SMTP commands are used for this form of submission.
983 A local process may also make a TCP/IP call to the host's loopback address
984 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
985 does not treat the loopback address specially. It treats all such connections
986 in the same way as connections from other hosts.
990 .cindex "message sender" "constructed by Exim"
991 .cindex "sender" "constructed by Exim"
992 In the three cases that do not involve TCP/IP, the sender address is
993 constructed from the login name of the user that called Exim and a default
994 qualification domain (which can be set by the &%qualify_domain%& configuration
995 option). For local or batch SMTP, a sender address that is passed using the
996 SMTP MAIL command is ignored. However, the system administrator may allow
997 certain users (&"trusted users"&) to specify a different sender address
998 unconditionally, or all users to specify certain forms of different sender
999 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1000 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1001 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1002 users to change sender addresses.
1004 Messages received by either of the non-interactive mechanisms are subject to
1005 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1006 (either over TCP/IP, or interacting with a local process) can be checked by a
1007 number of ACLs that operate at different times during the SMTP session. Either
1008 individual recipients, or the entire message, can be rejected if local policy
1009 requirements are not met. The &[local_scan()]& function (see chapter
1010 &<<CHAPlocalscan>>&) is run for all incoming messages.
1012 Exim can be configured not to start a delivery process when a message is
1013 received; this can be unconditional, or depend on the number of incoming SMTP
1014 connections or the system load. In these situations, new messages wait on the
1015 queue until a queue runner process picks them up. However, in standard
1016 configurations under normal conditions, delivery is started as soon as a
1017 message is received.
1023 .section "Handling an incoming message"
1024 .cindex "spool directory" "files that hold a message"
1025 .cindex "file" "how a message is held"
1026 When Exim accepts a message, it writes two files in its spool directory. The
1027 first contains the envelope information, the current status of the message, and
1028 the header lines, and the second contains the body of the message. The names of
1029 the two spool files consist of the message id, followed by &`-H`& for the
1030 file containing the envelope and header, and &`-D`& for the data file.
1032 .cindex "spool directory" "&_input_& sub-directory"
1033 By default all these message files are held in a single directory called
1034 &_input_& inside the general Exim spool directory. Some operating systems do
1035 not perform very well if the number of files in a directory gets very large; to
1036 improve performance in such cases, the &%split_spool_directory%& option can be
1037 used. This causes Exim to split up the input files into 62 sub-directories
1038 whose names are single letters or digits.
1040 The envelope information consists of the address of the message's sender and
1041 the addresses of the recipients. This information is entirely separate from
1042 any addresses contained in the header lines. The status of the message includes
1043 a list of recipients who have already received the message. The format of the
1044 first spool file is described in chapter &<<CHAPspool>>&.
1046 .cindex "rewriting" "addresses"
1047 Address rewriting that is specified in the rewrite section of the configuration
1048 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1049 both in the header lines and the envelope, at the time the message is accepted.
1050 If during the course of delivery additional addresses are generated (for
1051 example, via aliasing), these new addresses are rewritten as soon as they are
1052 generated. At the time a message is actually delivered (transported) further
1053 rewriting can take place; because this is a transport option, it can be
1054 different for different forms of delivery. It is also possible to specify the
1055 addition or removal of certain header lines at the time the message is
1056 delivered (see chapters &<<CHAProutergeneric>>& and
1057 &<<CHAPtransportgeneric>>&).
1061 .section "Life of a message"
1062 .cindex "message" "life of"
1063 .cindex "message" "frozen"
1064 A message remains in the spool directory until it is completely delivered to
1065 its recipients or to an error address, or until it is deleted by an
1066 administrator or by the user who originally created it. In cases when delivery
1067 cannot proceed &-- for example, when a message can neither be delivered to its
1068 recipients nor returned to its sender, the message is marked &"frozen"& on the
1069 spool, and no more deliveries are attempted.
1071 .cindex "frozen messages" "thawing"
1072 .cindex "message" "thawing frozen"
1073 An administrator can &"thaw"& such messages when the problem has been
1074 corrected, and can also freeze individual messages by hand if necessary. In
1075 addition, an administrator can force a delivery error, causing a bounce message
1078 .cindex "&%timeout_frozen_after%&"
1079 .cindex "&%ignore_bounce_errors_after%&"
1080 There are options called &%ignore_bounce_errors_after%& and
1081 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1082 The first applies only to frozen bounces, the second to any frozen messages.
1084 .cindex "message" "log file for"
1085 .cindex "log" "file for each message"
1086 While Exim is working on a message, it writes information about each delivery
1087 attempt to its main log file. This includes successful, unsuccessful, and
1088 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1089 lines are also written to a separate &'message log'& file for each message.
1090 These logs are solely for the benefit of the administrator, and are normally
1091 deleted along with the spool files when processing of a message is complete.
1092 The use of individual message logs can be disabled by setting
1093 &%no_message_logs%&; this might give an improvement in performance on very busy
1096 .cindex "journal file"
1097 .cindex "file" "journal"
1098 All the information Exim itself needs to set up a delivery is kept in the first
1099 spool file, along with the header lines. When a successful delivery occurs, the
1100 address is immediately written at the end of a journal file, whose name is the
1101 message id followed by &`-J`&. At the end of a delivery run, if there are some
1102 addresses left to be tried again later, the first spool file (the &`-H`& file)
1103 is updated to indicate which these are, and the journal file is then deleted.
1104 Updating the spool file is done by writing a new file and renaming it, to
1105 minimize the possibility of data loss.
1107 Should the system or the program crash after a successful delivery but before
1108 the spool file has been updated, the journal is left lying around. The next
1109 time Exim attempts to deliver the message, it reads the journal file and
1110 updates the spool file before proceeding. This minimizes the chances of double
1111 deliveries caused by crashes.
1115 .section "Processing an address for delivery" "SECTprocaddress"
1116 .cindex "drivers" "definition of"
1117 .cindex "router" "definition of"
1118 .cindex "transport" "definition of"
1119 The main delivery processing elements of Exim are called &'routers'& and
1120 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1121 number of them is provided in the source distribution, and compile-time options
1122 specify which ones are included in the binary. Run time options specify which
1123 ones are actually used for delivering messages.
1125 .cindex "drivers" "instance definition"
1126 Each driver that is specified in the run time configuration is an &'instance'&
1127 of that particular driver type. Multiple instances are allowed; for example,
1128 you can set up several different &(smtp)& transports, each with different
1129 option values that might specify different ports or different timeouts. Each
1130 instance has its own identifying name. In what follows we will normally use the
1131 instance name when discussing one particular instance (that is, one specific
1132 configuration of the driver), and the generic driver name when discussing
1133 the driver's features in general.
1135 A &'router'& is a driver that operates on an address, either determining how
1136 its delivery should happen, by assigning it to a specific transport, or
1137 converting the address into one or more new addresses (for example, via an
1138 alias file). A router may also explicitly choose to fail an address, causing it
1141 A &'transport'& is a driver that transmits a copy of the message from Exim's
1142 spool to some destination. There are two kinds of transport: for a &'local'&
1143 transport, the destination is a file or a pipe on the local host, whereas for a
1144 &'remote'& transport the destination is some other host. A message is passed
1145 to a specific transport as a result of successful routing. If a message has
1146 several recipients, it may be passed to a number of different transports.
1148 .cindex "preconditions" "definition of"
1149 An address is processed by passing it to each configured router instance in
1150 turn, subject to certain preconditions, until a router accepts the address or
1151 specifies that it should be bounced. We will describe this process in more
1152 detail shortly. First, as a simple example, we consider how each recipient
1153 address in a message is processed in a small configuration of three routers.
1155 To make this a more concrete example, it is described in terms of some actual
1156 routers, but remember, this is only an example. You can configure Exim's
1157 routers in many different ways, and there may be any number of routers in a
1160 The first router that is specified in a configuration is often one that handles
1161 addresses in domains that are not recognized specially by the local host. These
1162 are typically addresses for arbitrary domains on the Internet. A precondition
1163 is set up which looks for the special domains known to the host (for example,
1164 its own domain name), and the router is run for addresses that do &'not'&
1165 match. Typically, this is a router that looks up domains in the DNS in order to
1166 find the hosts to which this address routes. If it succeeds, the address is
1167 assigned to a suitable SMTP transport; if it does not succeed, the router is
1168 configured to fail the address.
1170 The second router is reached only when the domain is recognized as one that
1171 &"belongs"& to the local host. This router does redirection &-- also known as
1172 aliasing and forwarding. When it generates one or more new addresses from the
1173 original, each of them is routed independently from the start. Otherwise, the
1174 router may cause an address to fail, or it may simply decline to handle the
1175 address, in which case the address is passed to the next router.
1177 The final router in many configurations is one that checks to see if the
1178 address belongs to a local mailbox. The precondition may involve a check to
1179 see if the local part is the name of a login account, or it may look up the
1180 local part in a file or a database. If its preconditions are not met, or if
1181 the router declines, we have reached the end of the routers. When this happens,
1182 the address is bounced.
1186 .section "Processing an address for verification"
1187 .cindex "router" "for verification"
1188 .cindex "verifying address" "overview"
1189 As well as being used to decide how to deliver to an address, Exim's routers
1190 are also used for &'address verification'&. Verification can be requested as
1191 one of the checks to be performed in an ACL for incoming messages, on both
1192 sender and recipient addresses, and it can be tested using the &%-bv%& and
1193 &%-bvs%& command line options.
1195 When an address is being verified, the routers are run in &"verify mode"&. This
1196 does not affect the way the routers work, but it is a state that can be
1197 detected. By this means, a router can be skipped or made to behave differently
1198 when verifying. A common example is a configuration in which the first router
1199 sends all messages to a message-scanning program, unless they have been
1200 previously scanned. Thus, the first router accepts all addresses without any
1201 checking, making it useless for verifying. Normally, the &%no_verify%& option
1202 would be set for such a router, causing it to be skipped in verify mode.
1207 .section "Running an individual router" "SECTrunindrou"
1208 .cindex "router" "running details"
1209 .cindex "preconditions" "checking"
1210 .cindex "router" "result of running"
1211 As explained in the example above, a number of preconditions are checked before
1212 running a router. If any are not met, the router is skipped, and the address is
1213 passed to the next router. When all the preconditions on a router &'are'& met,
1214 the router is run. What happens next depends on the outcome, which is one of
1218 &'accept'&: The router accepts the address, and either assigns it to a
1219 transport, or generates one or more &"child"& addresses. Processing the
1220 original address ceases,
1221 .cindex "&%unseen%& option"
1222 unless the &%unseen%& option is set on the router. This option
1223 can be used to set up multiple deliveries with different routing (for example,
1224 for keeping archive copies of messages). When &%unseen%& is set, the address is
1225 passed to the next router. Normally, however, an &'accept'& return marks the
1228 Any child addresses generated by the router are processed independently,
1229 starting with the first router by default. It is possible to change this by
1230 setting the &%redirect_router%& option to specify which router to start at for
1231 child addresses. Unlike &%pass_router%& (see below) the router specified by
1232 &%redirect_router%& may be anywhere in the router configuration.
1234 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1235 requests that the address be passed to another router. By default the address
1236 is passed to the next router, but this can be changed by setting the
1237 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1238 must be below the current router (to avoid loops).
1240 &'decline'&: The router declines to accept the address because it does not
1241 recognize it at all. By default, the address is passed to the next router, but
1242 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1243 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1244 &'decline'& into &'fail'&.
1246 &'fail'&: The router determines that the address should fail, and queues it for
1247 the generation of a bounce message. There is no further processing of the
1248 original address unless &%unseen%& is set on the router.
1250 &'defer'&: The router cannot handle the address at the present time. (A
1251 database may be offline, or a DNS lookup may have timed out.) No further
1252 processing of the address happens in this delivery attempt. It is tried again
1253 next time the message is considered for delivery.
1255 &'error'&: There is some error in the router (for example, a syntax error in
1256 its configuration). The action is as for defer.
1259 If an address reaches the end of the routers without having been accepted by
1260 any of them, it is bounced as unrouteable. The default error message in this
1261 situation is &"unrouteable address"&, but you can set your own message by
1262 making use of the &%cannot_route_message%& option. This can be set for any
1263 router; the value from the last router that &"saw"& the address is used.
1265 Sometimes while routing you want to fail a delivery when some conditions are
1266 met but others are not, instead of passing the address on for further routing.
1267 You can do this by having a second router that explicitly fails the delivery
1268 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1269 facility for this purpose.
1272 .section "Duplicate addresses"
1273 .cindex "case of local parts"
1274 .cindex "address duplicate" "discarding"
1275 Once routing is complete, Exim scans the addresses that are assigned to local
1276 and remote transports, and discards any duplicates that it finds. During this
1277 check, local parts are treated as case-sensitive.
1280 .section "Router preconditions" "SECTrouprecon"
1281 .cindex "router preconditions" "order of processing"
1282 .cindex "preconditions" "order of processing"
1283 The preconditions that are tested for each router are listed below, in the
1284 order in which they are tested. The individual configuration options are
1285 described in more detail in chapter &<<CHAProutergeneric>>&.
1288 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1289 the local parts handled by the router may or must have certain prefixes and/or
1290 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1291 skipped. These conditions are tested first. When an affix is present, it is
1292 removed from the local part before further processing, including the evaluation
1293 of any other conditions.
1295 Routers can be designated for use only when not verifying an address, that is,
1296 only when routing it for delivery (or testing its delivery routing). If the
1297 &%verify%& option is set false, the router is skipped when Exim is verifying an
1299 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1300 &%verify_recipient%&, which independently control the use of the router for
1301 sender and recipient verification. You can set these options directly if
1302 you want a router to be used for only one type of verification.
1304 If the &%address_test%& option is set false, the router is skipped when Exim is
1305 run with the &%-bt%& option to test an address routing. This can be helpful
1306 when the first router sends all new messages to a scanner of some sort; it
1307 makes it possible to use &%-bt%& to test subsequent delivery routing without
1308 having to simulate the effect of the scanner.
1310 Routers can be designated for use only when verifying an address, as
1311 opposed to routing it for delivery. The &%verify_only%& option controls this.
1313 Individual routers can be explicitly skipped when running the routers to
1314 check an address given in the SMTP EXPN command (see the &%expn%& option).
1316 If the &%domains%& option is set, the domain of the address must be in the set
1317 of domains that it defines.
1319 .cindex "&$local_part_prefix$&"
1320 .cindex "&$local_part$&"
1321 .cindex "&$local_part_suffix$&"
1322 If the &%local_parts%& option is set, the local part of the address must be in
1323 the set of local parts that it defines. If &%local_part_prefix%& or
1324 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1325 part before this check. If you want to do precondition tests on local parts
1326 that include affixes, you can do so by using a &%condition%& option (see below)
1327 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1328 &$local_part_suffix$& as necessary.
1330 .cindex "&$local_user_uid$&"
1331 .cindex "&$local_user_gid$&"
1333 If the &%check_local_user%& option is set, the local part must be the name of
1334 an account on the local host. If this check succeeds, the uid and gid of the
1335 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1336 user's home directory is placed in &$home$&; these values can be used in the
1337 remaining preconditions.
1339 If the &%router_home_directory%& option is set, it is expanded at this point,
1340 because it overrides the value of &$home$&. If this expansion were left till
1341 later, the value of &$home$& as set by &%check_local_user%& would be used in
1342 subsequent tests. Having two different values of &$home$& in the same router
1343 could lead to confusion.
1345 If the &%senders%& option is set, the envelope sender address must be in the
1346 set of addresses that it defines.
1348 If the &%require_files%& option is set, the existence or non-existence of
1349 specified files is tested.
1351 .cindex "customizing" "precondition"
1352 If the &%condition%& option is set, it is evaluated and tested. This option
1353 uses an expanded string to allow you to set up your own custom preconditions.
1354 Expanded strings are described in chapter &<<CHAPexpand>>&.
1358 Note that &%require_files%& comes near the end of the list, so you cannot use
1359 it to check for the existence of a file in which to lookup up a domain, local
1360 part, or sender. However, as these options are all expanded, you can use the
1361 &%exists%& expansion condition to make such tests within each condition. The
1362 &%require_files%& option is intended for checking files that the router may be
1363 going to use internally, or which are needed by a specific transport (for
1364 example, &_.procmailrc_&).
1368 .section "Delivery in detail"
1369 .cindex "delivery" "in detail"
1370 When a message is to be delivered, the sequence of events is as follows:
1373 If a system-wide filter file is specified, the message is passed to it. The
1374 filter may add recipients to the message, replace the recipients, discard the
1375 message, cause a new message to be generated, or cause the message delivery to
1376 fail. The format of the system filter file is the same as for Exim user filter
1377 files, described in the separate document entitled &'Exim's interfaces to mail
1379 .cindex "Sieve filter" "not available for system filter"
1380 (&*Note*&: Sieve cannot be used for system filter files.)
1382 Some additional features are available in system filters &-- see chapter
1383 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1384 filter only once per delivery attempt, however many recipients it has. However,
1385 if there are several delivery attempts because one or more addresses could not
1386 be immediately delivered, the system filter is run each time. The filter
1387 condition &%first_delivery%& can be used to detect the first run of the system
1390 Each recipient address is offered to each configured router in turn, subject to
1391 its preconditions, until one is able to handle it. If no router can handle the
1392 address, that is, if they all decline, the address is failed. Because routers
1393 can be targeted at particular domains, several locally handled domains can be
1394 processed entirely independently of each other.
1396 .cindex "routing" "loops in"
1397 .cindex "loop" "while routing"
1398 A router that accepts an address may assign it to a local or a remote
1399 transport. However, the transport is not run at this time. Instead, the address
1400 is placed on a list for the particular transport, which will be run later.
1401 Alternatively, the router may generate one or more new addresses (typically
1402 from alias, forward, or filter files). New addresses are fed back into this
1403 process from the top, but in order to avoid loops, a router ignores any address
1404 which has an identically-named ancestor that was processed by itself.
1406 When all the routing has been done, addresses that have been successfully
1407 handled are passed to their assigned transports. When local transports are
1408 doing real local deliveries, they handle only one address at a time, but if a
1409 local transport is being used as a pseudo-remote transport (for example, to
1410 collect batched SMTP messages for transmission by some other means) multiple
1411 addresses can be handled. Remote transports can always handle more than one
1412 address at a time, but can be configured not to do so, or to restrict multiple
1413 addresses to the same domain.
1415 Each local delivery to a file or a pipe runs in a separate process under a
1416 non-privileged uid, and these deliveries are run one at a time. Remote
1417 deliveries also run in separate processes, normally under a uid that is private
1418 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1419 run in parallel. The maximum number of simultaneous remote deliveries for any
1420 one message is set by the &%remote_max_parallel%& option.
1421 The order in which deliveries are done is not defined, except that all local
1422 deliveries happen before any remote deliveries.
1424 .cindex "queue runner"
1425 When it encounters a local delivery during a queue run, Exim checks its retry
1426 database to see if there has been a previous temporary delivery failure for the
1427 address before running the local transport. If there was a previous failure,
1428 Exim does not attempt a new delivery until the retry time for the address is
1429 reached. However, this happens only for delivery attempts that are part of a
1430 queue run. Local deliveries are always attempted when delivery immediately
1431 follows message reception, even if retry times are set for them. This makes for
1432 better behaviour if one particular message is causing problems (for example,
1433 causing quota overflow, or provoking an error in a filter file).
1435 .cindex "delivery" "retry in remote transports"
1436 Remote transports do their own retry handling, since an address may be
1437 deliverable to one of a number of hosts, each of which may have a different
1438 retry time. If there have been previous temporary failures and no host has
1439 reached its retry time, no delivery is attempted, whether in a queue run or
1440 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1442 If there were any permanent errors, a bounce message is returned to an
1443 appropriate address (the sender in the common case), with details of the error
1444 for each failing address. Exim can be configured to send copies of bounce
1445 messages to other addresses.
1447 .cindex "delivery" "deferral"
1448 If one or more addresses suffered a temporary failure, the message is left on
1449 the queue, to be tried again later. Delivery of these addresses is said to be
1452 When all the recipient addresses have either been delivered or bounced,
1453 handling of the message is complete. The spool files and message log are
1454 deleted, though the message log can optionally be preserved if required.
1460 .section "Retry mechanism"
1461 .cindex "delivery" "retry mechanism"
1462 .cindex "retry" "description of mechanism"
1463 .cindex "queue runner"
1464 Exim's mechanism for retrying messages that fail to get delivered at the first
1465 attempt is the queue runner process. You must either run an Exim daemon that
1466 uses the &%-q%& option with a time interval to start queue runners at regular
1467 intervals, or use some other means (such as &'cron'&) to start them. If you do
1468 not arrange for queue runners to be run, messages that fail temporarily at the
1469 first attempt will remain on your queue for ever. A queue runner process works
1470 its way through the queue, one message at a time, trying each delivery that has
1471 passed its retry time.
1472 You can run several queue runners at once.
1474 Exim uses a set of configured rules to determine when next to retry the failing
1475 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1476 should give up trying to deliver to the address, at which point it generates a
1477 bounce message. If no retry rules are set for a particular host, address, and
1478 error combination, no retries are attempted, and temporary errors are treated
1483 .section "Temporary delivery failure"
1484 .cindex "delivery" "temporary failure"
1485 There are many reasons why a message may not be immediately deliverable to a
1486 particular address. Failure to connect to a remote machine (because it, or the
1487 connection to it, is down) is one of the most common. Temporary failures may be
1488 detected during routing as well as during the transport stage of delivery.
1489 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1490 is on a file system where the user is over quota. Exim can be configured to
1491 impose its own quotas on local mailboxes; where system quotas are set they will
1494 If a host is unreachable for a period of time, a number of messages may be
1495 waiting for it by the time it recovers, and sending them in a single SMTP
1496 connection is clearly beneficial. Whenever a delivery to a remote host is
1499 .cindex "hints database"
1500 Exim makes a note in its hints database, and whenever a successful
1501 SMTP delivery has happened, it looks to see if any other messages are waiting
1502 for the same host. If any are found, they are sent over the same SMTP
1503 connection, subject to a configuration limit as to the maximum number in any
1509 .section "Permanent delivery failure"
1510 .cindex "delivery" "permanent failure"
1511 .cindex "bounce message" "when generated"
1512 When a message cannot be delivered to some or all of its intended recipients, a
1513 bounce message is generated. Temporary delivery failures turn into permanent
1514 errors when their timeout expires. All the addresses that fail in a given
1515 delivery attempt are listed in a single message. If the original message has
1516 many recipients, it is possible for some addresses to fail in one delivery
1517 attempt and others to fail subsequently, giving rise to more than one bounce
1518 message. The wording of bounce messages can be customized by the administrator.
1519 See chapter &<<CHAPemsgcust>>& for details.
1521 .cindex "&'X-Failed-Recipients:'& header line"
1522 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1523 failed addresses, for the benefit of programs that try to analyse such messages
1526 .cindex "bounce message" "recipient of"
1527 A bounce message is normally sent to the sender of the original message, as
1528 obtained from the message's envelope. For incoming SMTP messages, this is the
1529 address given in the MAIL command. However, when an address is expanded via a
1530 forward or alias file, an alternative address can be specified for delivery
1531 failures of the generated addresses. For a mailing list expansion (see section
1532 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1537 .section "Failures to deliver bounce messages"
1538 .cindex "bounce message" "failure to deliver"
1539 If a bounce message (either locally generated or received from a remote host)
1540 itself suffers a permanent delivery failure, the message is left on the queue,
1541 but it is frozen, awaiting the attention of an administrator. There are options
1542 that can be used to make Exim discard such failed messages, or to keep them
1543 for only a short time (see &%timeout_frozen_after%& and
1544 &%ignore_bounce_errors_after%&).
1550 . ////////////////////////////////////////////////////////////////////////////
1551 . ////////////////////////////////////////////////////////////////////////////
1553 .chapter "Building and installing Exim"
1554 .scindex IIDbuex "building Exim"
1556 .section "Unpacking"
1557 Exim is distributed as a gzipped or bzipped tar file which, when upacked,
1558 creates a directory with the name of the current release (for example,
1559 &_exim-&version;_&) into which the following files are placed:
1562 .row &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1563 .row &_CHANGES_& "contains a reference to where changes are documented"
1564 .row &_LICENCE_& "the GNU General Public Licence"
1565 .row &_Makefile_& "top-level make file"
1566 .row &_NOTICE_& "conditions for the use of Exim"
1567 .row &_README_& "list of files, directories and simple build &&&
1571 Other files whose names begin with &_README_& may also be present. The
1572 following subdirectories are created:
1575 .row &_Local_& "an empty directory for local configuration files"
1576 .row &_OS_& "OS-specific files"
1577 .row &_doc_& "documentation files"
1578 .row &_exim_monitor_& "source files for the Exim monitor"
1579 .row &_scripts_& "scripts used in the build process"
1580 .row &_src_& "remaining source files"
1581 .row &_util_& "independent utilities"
1584 The main utility programs are contained in the &_src_& directory, and are built
1585 with the Exim binary. The &_util_& directory contains a few optional scripts
1586 that may be useful to some sites.
1589 .section "Multiple machine architectures and operating systems"
1590 .cindex "building Exim" "multiple OS/architectures"
1591 The building process for Exim is arranged to make it easy to build binaries for
1592 a number of different architectures and operating systems from the same set of
1593 source files. Compilation does not take place in the &_src_& directory.
1594 Instead, a &'build directory'& is created for each architecture and operating
1596 .cindex "symbolic link" "to build directory"
1597 Symbolic links to the sources are installed in this directory, which is where
1598 the actual building takes place. In most cases, Exim can discover the machine
1599 architecture and operating system for itself, but the defaults can be
1600 overridden if necessary.
1603 .section "DBM libraries" "SECTdb"
1604 .cindex "DBM libraries" "discussion of"
1605 .cindex "hints database" "DBM files used for"
1606 Even if you do not use any DBM files in your configuration, Exim still needs a
1607 DBM library in order to operate, because it uses indexed files for its hints
1608 databases. Unfortunately, there are a number of DBM libraries in existence, and
1609 different operating systems often have different ones installed.
1611 .cindex "Solaris" "DBM library for"
1612 .cindex "IRIX" "DBM library for"
1613 .cindex "BSD" "DBM library for"
1614 .cindex "Linux" "DBM library for"
1615 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1616 Linux distribution, the DBM configuration should happen automatically, and you
1617 may be able to ignore this section. Otherwise, you may have to learn more than
1618 you would like about DBM libraries from what follows.
1620 .cindex "&'ndbm'& DBM library"
1621 Licensed versions of Unix normally contain a library of DBM functions operating
1622 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1623 versions of Unix seem to vary in what they contain as standard. In particular,
1624 some early versions of Linux have no default DBM library, and different
1625 distributors have chosen to bundle different libraries with their packaged
1626 versions. However, the more recent releases seem to have standardised on the
1627 Berkeley DB library.
1629 Different DBM libraries have different conventions for naming the files they
1630 use. When a program opens a file called &_dbmfile_&, there are several
1634 A traditional &'ndbm'& implementation, such as that supplied as part of
1635 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1637 .cindex "&'gdbm'& DBM library"
1638 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1639 compatibility interface it makes two different hard links to it with names
1640 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1641 file name is used unmodified.
1643 .cindex "Berkeley DB library"
1644 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1645 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1646 programmer exactly the same as the traditional &'ndbm'& implementation.
1648 If the Berkeley package is used in its native mode, it operates on a single
1649 file called &_dbmfile_&; the programmer's interface is somewhat different to
1650 the traditional &'ndbm'& interface.
1652 To complicate things further, there are several very different versions of the
1653 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1654 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1655 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1656 versions of Berkeley DB can be obtained from
1657 &url(http://www.sleepycat.com/).
1659 .cindex "&'tdb'& DBM library"
1660 Yet another DBM library, called &'tdb'&, is available from
1661 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1662 operates on a single file.
1666 .cindex "DBM libraries" "configuration for building"
1667 Exim and its utilities can be compiled to use any of these interfaces. In order
1668 to use any version of the Berkeley DB package in native mode, you must set
1669 USE_DB in an appropriate configuration file (typically
1670 &_Local/Makefile_&). For example:
1674 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1675 error is diagnosed if you set more than one of these.
1677 At the lowest level, the build-time configuration sets none of these options,
1678 thereby assuming an interface of type (1). However, some operating system
1679 configuration files (for example, those for the BSD operating systems and
1680 Linux) assume type (4) by setting USE_DB as their default, and the
1681 configuration files for Cygwin set USE_GDBM. Anything you set in
1682 &_Local/Makefile_&, however, overrides these system defaults.
1684 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1685 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1686 in one of these lines:
1691 Settings like that will work if the DBM library is installed in the standard
1692 place. Sometimes it is not, and the library's header file may also not be in
1693 the default path. You may need to set INCLUDE to specify where the header
1694 file is, and to specify the path to the library more fully in DBMLIB, as in
1697 INCLUDE=-I/usr/local/include/db-4.1
1698 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1700 There is further detailed discussion about the various DBM libraries in the
1701 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1705 .section "Pre-building configuration"
1706 .cindex "building Exim" "pre-building configuration"
1707 .cindex "configuration for building Exim"
1708 .cindex "&_Local/Makefile_&"
1709 .cindex "&_src/EDITME_&"
1710 Before building Exim, a local configuration file that specifies options
1711 independent of any operating system has to be created with the name
1712 &_Local/Makefile_&. A template for this file is supplied as the file
1713 &_src/EDITME_&, and it contains full descriptions of all the option settings
1714 therein. These descriptions are therefore not repeated here. If you are
1715 building Exim for the first time, the simplest thing to do is to copy
1716 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1718 There are three settings that you must supply, because Exim will not build
1719 without them. They are the location of the run time configuration file
1720 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1721 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1722 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1723 a colon-separated list of file names; Exim uses the first of them that exists.
1725 There are a few other parameters that can be specified either at build time or
1726 at run time, to enable the same binary to be used on a number of different
1727 machines. However, if the locations of Exim's spool directory and log file
1728 directory (if not within the spool directory) are fixed, it is recommended that
1729 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1730 detected early in Exim's execution (such as a malformed configuration file) can
1733 .cindex "content scanning" "specifying at build time"
1734 Exim's interfaces for calling virus and spam scanning software directly from
1735 access control lists are not compiled by default. If you want to include these
1736 facilities, you need to set
1738 WITH_CONTENT_SCAN=yes
1740 in your &_Local/Makefile_&. For details of the facilities themselves, see
1741 chapter &<<CHAPexiscan>>&.
1744 .cindex "&_Local/eximon.conf_&"
1745 .cindex "_exim_monitor/EDITME_"
1746 If you are going to build the Exim monitor, a similar configuration process is
1747 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1748 your installation and saved under the name &_Local/eximon.conf_&. If you are
1749 happy with the default settings described in &_exim_monitor/EDITME_&,
1750 &_Local/eximon.conf_& can be empty, but it must exist.
1752 This is all the configuration that is needed in straightforward cases for known
1753 operating systems. However, the building process is set up so that it is easy
1754 to override options that are set by default or by operating-system-specific
1755 configuration files, for example to change the name of the C compiler, which
1756 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1761 .section "Support for iconv()"
1762 .cindex "&[iconv()]& support"
1764 The contents of header lines in messages may be encoded according to the rules
1765 described RFC 2047. This makes it possible to transmit characters that are not
1766 in the ASCII character set, and to label them as being in a particular
1767 character set. When Exim is inspecting header lines by means of the &%$h_%&
1768 mechanism, it decodes them, and translates them into a specified character set
1769 (default ISO-8859-1). The translation is possible only if the operating system
1770 supports the &[iconv()]& function.
1772 However, some of the operating systems that supply &[iconv()]& do not support
1773 very many conversions. The GNU &%libiconv%& library (available from
1774 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1775 systems to remedy this deficiency, as well as on systems that do not supply
1776 &[iconv()]& at all. After installing &%libiconv%&, you should add
1780 to your &_Local/Makefile_& and rebuild Exim.
1784 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1785 .cindex "TLS" "including support for TLS"
1786 .cindex "encryption" "including support for"
1787 .cindex "SUPPORT_TLS"
1788 .cindex "OpenSSL" "building Exim with"
1789 .cindex "GnuTLS" "building Exim with"
1790 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1791 command as per RFC 2487. It can also support legacy clients that expect to
1792 start a TLS session immediately on connection to a non-standard port (see the
1793 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1796 If you want to build Exim with TLS support, you must first install either the
1797 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1800 If OpenSSL is installed, you should set
1803 TLS_LIBS=-lssl -lcrypto
1805 in &_Local/Makefile_&. You may also need to specify the locations of the
1806 OpenSSL library and include files. For example:
1809 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1810 TLS_INCLUDE=-I/usr/local/openssl/include/
1812 .cindex "USE_GNUTLS"
1813 If GnuTLS is installed, you should set
1817 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1819 in &_Local/Makefile_&, and again you may need to specify the locations of the
1820 library and include files. For example:
1824 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1825 TLS_INCLUDE=-I/usr/gnu/include
1827 You do not need to set TLS_INCLUDE if the relevant directory is already
1828 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1829 given in chapter &<<CHAPTLS>>&.
1834 .section "Use of tcpwrappers"
1835 .cindex "tcpwrappers" "building Exim to support"
1836 .cindex "USE_TCP_WRAPPERS"
1837 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1838 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1839 alternative to Exim's own checking facilities for installations that are
1840 already making use of &'tcpwrappers'& for other purposes. To do this, you
1841 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1842 &_tcpd.h_& to be available at compile time, and also ensure that the library
1843 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1844 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1847 USE_TCP_WRAPPERS=yes
1848 CFLAGS=-O -I/usr/local/include
1849 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1851 in &_Local/Makefile_&. The name to use in the &'tcpwrappers'& control files is
1852 &"exim"&. For example, the line
1854 exim : LOCAL 192.168.1. .friendly.domain.example
1856 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1857 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1858 All other connections are denied. Consult the &'tcpwrappers'& documentation for
1863 .section "Including support for IPv6"
1864 .cindex "IPv6" "including support for"
1865 Exim contains code for use on systems that have IPv6 support. Setting
1866 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1867 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1868 where the IPv6 support is not fully integrated into the normal include and
1871 Two different types of DNS record for handling IPv6 addresses have been
1872 defined. AAAA records (analagous to A records for IPv4) are in use, and are
1873 currently seen as the mainstream. Another record type called A6 was proposed
1874 as better than AAAA because it had more flexibility. However, it was felt to be
1875 over-complex, and its status was reduced to &"experimental"&. It is not known
1876 if anyone is actually using A6 records. Exim has support for A6 records, but
1877 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1878 support has not been tested for some time.
1882 .section "The building process"
1883 .cindex "build directory"
1884 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
1885 created, run &'make'& at the top level. It determines the architecture and
1886 operating system types, and creates a build directory if one does not exist.
1887 For example, on a Sun system running Solaris 8, the directory
1888 &_build-SunOS5-5.8-sparc_& is created.
1889 .cindex "symbolic link" "to source files"
1890 Symbolic links to relevant source files are installed in the build directory.
1892 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
1893 building process fails if it is set.
1895 If this is the first time &'make'& has been run, it calls a script that builds
1896 a make file inside the build directory, using the configuration files from the
1897 &_Local_& directory. The new make file is then passed to another instance of
1898 &'make'&. This does the real work, building a number of utility scripts, and
1899 then compiling and linking the binaries for the Exim monitor (if configured), a
1900 number of utility programs, and finally Exim itself. The command &`make
1901 makefile`& can be used to force a rebuild of the make file in the build
1902 directory, should this ever be necessary.
1904 If you have problems building Exim, check for any comments there may be in the
1905 &_README_& file concerning your operating system, and also take a look at the
1906 FAQ, where some common problems are covered.
1910 .section 'Output from &"make"&'
1911 The output produced by the &'make'& process for compile lines is often very
1912 unreadable, because these lines can be very long. For this reason, the normal
1913 output is suppressed by default, and instead output similar to that which
1914 appears when compiling the 2.6 Linux kernel is generated: just a short line for
1915 each module that is being compiled or linked. However, it is still possible to
1916 get the full output, by calling &'make'& like this:
1920 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
1921 command reflection in &'make'&. When you ask for the full output, it is
1922 given in addition to the the short output.
1926 .section "Overriding build-time options for Exim" "SECToverride"
1927 .cindex "build-time options" "overriding"
1928 The main make file that is created at the beginning of the building process
1929 consists of the concatenation of a number of files which set configuration
1930 values, followed by a fixed set of &'make'& instructions. If a value is set
1931 more than once, the last setting overrides any previous ones. This provides a
1932 convenient way of overriding defaults. The files that are concatenated are, in
1935 &_OS/Makefile-Default_&
1936 &_OS/Makefile-_&<&'ostype'&>
1938 &_Local/Makefile-_&<&'ostype'&>
1939 &_Local/Makefile-_&<&'archtype'&>
1940 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
1941 &_OS/Makefile-Base_&
1943 .cindex "&_Local/Makefile_&"
1944 .cindex "building Exim" "operating system type"
1945 .cindex "building Exim" "architecture type"
1946 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
1947 architecture type. &_Local/Makefile_& is required to exist, and the building
1948 process fails if it is absent. The other three &_Local_& files are optional,
1949 and are often not needed.
1951 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
1952 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
1953 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
1954 values are used, thereby providing a means of forcing particular settings.
1955 Otherwise, the scripts try to get values from the &%uname%& command. If this
1956 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
1957 of &'ad hoc'& transformations are then applied, to produce the standard names
1958 that Exim expects. You can run these scripts directly from the shell in order
1959 to find out what values are being used on your system.
1962 &_OS/Makefile-Default_& contains comments about the variables that are set
1963 therein. Some (but not all) are mentioned below. If there is something that
1964 needs changing, review the contents of this file and the contents of the make
1965 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
1969 .cindex "building Exim" "overriding default settings"
1970 If you need to change any of the values that are set in &_OS/Makefile-Default_&
1971 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
1972 need to change the original files. Instead, you should make the changes by
1973 putting the new values in an appropriate &_Local_& file. For example,
1974 .cindex "Tru64-Unix build-time settings"
1975 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
1976 formerly DEC-OSF1) operating system, it is necessary to specify that the C
1977 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
1978 called with the option &%-std1%&, to make it recognize some of the features of
1979 Standard C that Exim uses. (Most other compilers recognize Standard C by
1980 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
1981 containing the lines
1986 If you are compiling for just one operating system, it may be easier to put
1987 these lines directly into &_Local/Makefile_&.
1989 Keeping all your local configuration settings separate from the distributed
1990 files makes it easy to transfer them to new versions of Exim simply by copying
1991 the contents of the &_Local_& directory.
1994 .cindex "NIS lookup type" "including support for"
1995 .cindex "NIS+ lookup type" "including support for"
1996 .cindex "LDAP" "including support for"
1997 .cindex "lookup" "inclusion in binary"
1998 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
1999 lookup, but not all systems have these components installed, so the default is
2000 not to include the relevant code in the binary. All the different kinds of file
2001 and database lookup that Exim supports are implemented as separate code modules
2002 which are included only if the relevant compile-time options are set. In the
2003 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2009 and similar settings apply to the other lookup types. They are all listed in
2010 &_src/EDITME_&. In many cases the relevant include files and interface
2011 libraries need to be installed before compiling Exim.
2012 .cindex "cdb" "including support for"
2013 However, there are some optional lookup types (such as cdb) for which
2014 the code is entirely contained within Exim, and no external include
2015 files or libraries are required. When a lookup type is not included in the
2016 binary, attempts to configure Exim to use it cause run time configuration
2019 .cindex "Perl" "including support for"
2020 Exim can be linked with an embedded Perl interpreter, allowing Perl
2021 subroutines to be called during string expansion. To enable this facility,
2025 must be defined in &_Local/Makefile_&. Details of this facility are given in
2026 chapter &<<CHAPperl>>&.
2028 .cindex "X11 libraries" "location of"
2029 The location of the X11 libraries is something that varies a lot between
2030 operating systems, and there may be different versions of X11 to cope
2031 with. Exim itself makes no use of X11, but if you are compiling the Exim
2032 monitor, the X11 libraries must be available.
2033 The following three variables are set in &_OS/Makefile-Default_&:
2036 XINCLUDE=-I$(X11)/include
2037 XLFLAGS=-L$(X11)/lib
2039 These are overridden in some of the operating-system configuration files. For
2040 example, in &_OS/Makefile-SunOS5_& there is
2043 XINCLUDE=-I$(X11)/include
2044 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2046 If you need to override the default setting for your operating system, place a
2047 definition of all three of these variables into your
2048 &_Local/Makefile-<ostype>_& file.
2051 If you need to add any extra libraries to the link steps, these can be put in a
2052 variable called EXTRALIBS, which appears in all the link commands, but by
2053 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2054 command for linking the main Exim binary, and not for any associated utilities.
2056 .cindex "DBM libraries" "configuration for building"
2057 There is also DBMLIB, which appears in the link commands for binaries that
2058 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2059 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2060 binary, and which can be used, for example, to include additional X11
2063 .cindex "configuration file" "editing"
2064 The make file copes with rebuilding Exim correctly if any of the configuration
2065 files are edited. However, if an optional configuration file is deleted, it is
2066 necessary to touch the associated non-optional file (that is,
2067 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2070 .section "OS-specific header files"
2072 .cindex "building Exim" "OS-specific C header files"
2073 The &_OS_& directory contains a number of files with names of the form
2074 &_os.h-<ostype>_&. These are system-specific C header files that should not
2075 normally need to be changed. There is a list of macro settings that are
2076 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2077 are porting Exim to a new operating system.
2081 .section "Overriding build-time options for the monitor"
2082 .cindex "building Eximon" "overriding default options"
2083 A similar process is used for overriding things when building the Exim monitor,
2084 where the files that are involved are
2086 &_OS/eximon.conf-Default_&
2087 &_OS/eximon.conf-_&<&'ostype'&>
2088 &_Local/eximon.conf_&
2089 &_Local/eximon.conf-_&<&'ostype'&>
2090 &_Local/eximon.conf-_&<&'archtype'&>
2091 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2093 .cindex "&_Local/eximon.conf_&"
2094 As with Exim itself, the final three files need not exist, and in this case the
2095 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2096 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2097 variables of the same name, preceded by EXIMON_. For example, setting
2098 EXIMON_LOG_DEPTH in the environment overrides the value of
2099 LOG_DEPTH at run time.
2103 .section "Installing Exim binaries and scripts"
2104 .cindex "installing Exim"
2105 .cindex "BIN_DIRECTORY"
2106 The command &`make install`& runs the &(exim_install)& script with no
2107 arguments. The script copies binaries and utility scripts into the directory
2108 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2109 .cindex "setuid" "installing Exim with"
2110 The install script copies files only if they are newer than the files they are
2111 going to replace. The Exim binary is required to be owned by root and have the
2112 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2113 install`& as root so that it can set up the Exim binary in this way. However, in
2114 some special situations (for example, if a host is doing no local deliveries)
2115 it may be possible to run Exim without making the binary setuid root (see
2116 chapter &<<CHAPsecurity>>& for details).
2118 .cindex "CONFIGURE_FILE"
2119 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2120 in &_Local/Makefile_&. If this names a single file, and the file does not
2121 exist, the default configuration file &_src/configure.default_& is copied there
2122 by the installation script. If a run time configuration file already exists, it
2123 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2124 alternative files, no default is installed.
2126 .cindex "system aliases file"
2127 .cindex "&_/etc/aliases_&"
2128 One change is made to the default configuration file when it is installed: the
2129 default configuration contains a router that references a system aliases file.
2130 The path to this file is set to the value specified by
2131 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2132 If the system aliases file does not exist, the installation script creates it,
2133 and outputs a comment to the user.
2135 The created file contains no aliases, but it does contain comments about the
2136 aliases a site should normally have. Mail aliases have traditionally been
2137 kept in &_/etc/aliases_&. However, some operating systems are now using
2138 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2139 Exim's configuration if necessary.
2141 The default configuration uses the local host's name as the only local domain,
2142 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2143 running as the local user. System aliases and &_.forward_& files in users' home
2144 directories are supported, but no NIS or NIS+ support is configured. Domains
2145 other than the name of the local host are routed using the DNS, with delivery
2148 It is possible to install Exim for special purposes (such as building a binary
2149 distribution) in a private part of the file system. You can do this by a
2152 make DESTDIR=/some/directory/ install
2154 This has the effect of pre-pending the specified directory to all the file
2155 paths, except the name of the system aliases file that appears in the default
2156 configuration. (If a default alias file is created, its name &'is'& modified.)
2157 For backwards compatibility, ROOT is used if DESTDIR is not set,
2158 but this usage is deprecated.
2160 .cindex "installing Exim" "what is not installed"
2161 Running &'make install'& does not copy the Exim 4 conversion script
2162 &'convert4r4'&, or the &'pcretest'& test program. You will probably run the
2163 first of these only once (if you are upgrading from Exim 3), and the second
2164 isn't really part of Exim. None of the documentation files in the &_doc_&
2165 directory are copied, except for the info files when you have set
2166 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2168 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2169 to their names. The Exim binary itself, however, is handled differently. It is
2170 installed under a name that includes the version number and the compile number,
2171 for example &_exim-&version;-1_&. The script then arranges for a symbolic link
2172 called &_exim_& to point to the binary. If you are updating a previous version
2173 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2174 from the directory (as seen by other processes).
2176 .cindex "installing Exim" "testing the script"
2177 If you want to see what the &'make install'& will do before running it for
2178 real, you can pass the &%-n%& option to the installation script by this
2181 make INSTALL_ARG=-n install
2183 The contents of the variable INSTALL_ARG are passed to the installation
2184 script. You do not need to be root to run this test. Alternatively, you can run
2185 the installation script directly, but this must be from within the build
2186 directory. For example, from the top-level Exim directory you could use this
2189 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2191 .cindex "installing Exim" "install script options"
2192 There are two other options that can be supplied to the installation script.
2195 &%-no_chown%& bypasses the call to change the owner of the installed binary
2196 to root, and the call to make it a setuid binary.
2198 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2202 INSTALL_ARG can be used to pass these options to the script. For example:
2204 make INSTALL_ARG=-no_symlink install
2206 The installation script can also be given arguments specifying which files are
2207 to be copied. For example, to install just the Exim binary, and nothing else,
2208 without creating the symbolic link, you could use:
2210 make INSTALL_ARG='-no_symlink exim' install
2215 .section "Installing info documentation" "SECTinsinfdoc"
2216 .cindex "installing Exim" "&'info'& documentation"
2217 Not all systems use the GNU &'info'& system for documentation, and for this
2218 reason, the Texinfo source of Exim's documentation is not included in the main
2219 distribution. Instead it is available separately from the ftp site (see section
2222 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2223 source of the documentation is found in the source tree, running &`make
2224 install`& automatically builds the info files and installs them.
2228 .section "Setting up the spool directory"
2229 .cindex "spool directory" "creating"
2230 When it starts up, Exim tries to create its spool directory if it does not
2231 exist. The Exim uid and gid are used for the owner and group of the spool
2232 directory. Sub-directories are automatically created in the spool directory as
2239 .cindex "testing" "installation"
2240 Having installed Exim, you can check that the run time configuration file is
2241 syntactically valid by running the following command, which assumes that the
2242 Exim binary directory is within your PATH environment variable:
2246 If there are any errors in the configuration file, Exim outputs error messages.
2247 Otherwise it outputs the version number and build date,
2248 the DBM library that is being used, and information about which drivers and
2249 other optional code modules are included in the binary.
2250 Some simple routing tests can be done by using the address testing option. For
2253 &`exim -bt`& <&'local username'&>
2255 should verify that it recognizes a local mailbox, and
2257 &`exim -bt`& <&'remote address'&>
2259 a remote one. Then try getting it to deliver mail, both locally and remotely.
2260 This can be done by passing messages directly to Exim, without going through a
2261 user agent. For example:
2263 exim -v postmaster@your.domain.example
2264 From: user@your.domain.example
2265 To: postmaster@your.domain.example
2266 Subject: Testing Exim
2268 This is a test message.
2271 The &%-v%& option causes Exim to output some verification of what it is doing.
2272 In this case you should see copies of three log lines, one for the message's
2273 arrival, one for its delivery, and one containing &"Completed"&.
2275 .cindex "delivery" "problems with"
2276 If you encounter problems, look at Exim's log files (&'mainlog'& and
2277 &'paniclog'&) to see if there is any relevant information there. Another source
2278 of information is running Exim with debugging turned on, by specifying the
2279 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2280 with debugging turned on by a command of the form
2282 &`exim -d -M`& <&'exim-message-id'&>
2284 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2285 produces rather a lot of output, but you can cut this down to specific areas.
2286 For example, if you use &%-d-all+route%& only the debugging information
2287 relevant to routing is included. (See the &%-d%& option in chapter
2288 &<<CHAPcommandline>>& for more details.)
2290 .cindex '&"sticky"& bit'
2291 .cindex "lock files"
2292 One specific problem that has shown up on some sites is the inability to do
2293 local deliveries into a shared mailbox directory, because it does not have the
2294 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2295 writing to a mailbox file, and if it cannot create the lock file, the delivery
2296 is deferred. You can get round this either by setting the &"sticky bit"& on the
2297 directory, or by setting a specific group for local deliveries and allowing
2298 that group to create files in the directory (see the comments above the
2299 &(local_delivery)& transport in the default configuration file). Another
2300 approach is to configure Exim not to use lock files, but just to rely on
2301 &[fcntl()]& locking instead. However, you should do this only if all user
2302 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2303 see chapter &<<CHAPappendfile>>&.
2305 One thing that cannot be tested on a system that is already running an MTA is
2306 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2307 &%-oX%& option can be used to run an Exim daemon that listens on some other
2308 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2309 &'exim_checkaccess'& utility can be used to check out policy controls on
2312 Testing a new version on a system that is already running Exim can most easily
2313 be done by building a binary with a different CONFIGURE_FILE setting. From
2314 within the run time configuration, all other file and directory names
2315 that Exim uses can be altered, in order to keep it entirely clear of the
2319 .section "Replacing another MTA with Exim"
2320 .cindex "replacing another MTA"
2321 Building and installing Exim for the first time does not of itself put it in
2322 general use. The name by which the system's MTA is called by mail user agents
2323 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2324 operating system), and it is necessary to make this name point to the &'exim'&
2325 binary in order to get the user agents to pass messages to Exim. This is
2326 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2327 or &_/usr/lib/sendmail_&
2328 .cindex "symbolic link" "to &'exim'& binary"
2329 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2330 privilege and executable status from the old MTA. It is then necessary to stop
2331 and restart the mailer daemon, if one is running.
2333 .cindex "FreeBSD" "MTA indirection"
2334 .cindex "&_/etc/mail/mailer.conf_&"
2335 Some operating systems have introduced alternative ways of switching MTAs. For
2336 example, if you are running FreeBSD, you need to edit the file
2337 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2338 described. A typical example of the contents of this file for running Exim is
2341 sendmail /usr/exim/bin/exim
2342 send-mail /usr/exim/bin/exim
2343 mailq /usr/exim/bin/exim -bp
2344 newaliases /usr/bin/true
2346 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2347 your Exim installation is &"live"&. Check it by sending a message from your
2348 favourite user agent.
2350 You should consider what to tell your users about the change of MTA. Exim may
2351 have different capabilities to what was previously running, and there are
2352 various operational differences such as the text of messages produced by
2353 command line options and in bounce messages. If you allow your users to make
2354 use of Exim's filtering capabilities, you should make the document entitled
2355 &'Exim's interface to mail filtering'& available to them.
2359 .section "Upgrading Exim"
2360 .cindex "upgrading Exim"
2361 If you are already running Exim on your host, building and installing a new
2362 version automatically makes it available to MUAs, or any other programs that
2363 call the MTA directly. However, if you are running an Exim daemon, you do need
2364 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2365 new binary. You do not need to stop processing mail in order to install a new
2366 version of Exim. The install script does not modify an existing runtime
2372 .section "Stopping the Exim daemon on Solaris"
2373 .cindex "Solaris" "stopping Exim on"
2374 The standard command for stopping the mailer daemon on Solaris is
2376 /etc/init.d/sendmail stop
2378 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2379 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2380 for the text &"sendmail"&; this is not present because the actual program name
2381 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2382 solution is to replace the line that finds the process id with something like
2384 pid=`cat /var/spool/exim/exim-daemon.pid`
2386 to obtain the daemon's pid directly from the file that Exim saves it in.
2388 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2389 still be received from local processes, and if automatic delivery is configured
2390 (the normal case), deliveries will still occur.
2395 . ////////////////////////////////////////////////////////////////////////////
2396 . ////////////////////////////////////////////////////////////////////////////
2398 .chapter "The Exim command line" "CHAPcommandline"
2399 .scindex IIDclo1 "command line" "options"
2400 .scindex IIDclo2 "options" "command line"
2401 Exim's command line takes the standard Unix form of a sequence of options,
2402 each starting with a hyphen character, followed by a number of arguments. The
2403 options are compatible with the main options of Sendmail, and there are also
2404 some additional options, some of which are compatible with Smail 3. Certain
2405 combinations of options do not make sense, and provoke an error if used.
2406 The form of the arguments depends on which options are set.
2409 .section "Setting options by program name"
2411 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2412 were present before any other options.
2413 The &%-bp%& option requests a listing of the contents of the mail queue on the
2415 This feature is for compatibility with some systems that contain a command of
2416 that name in one of the standard libraries, symbolically linked to
2417 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2420 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2421 were present before any other options, for compatibility with Smail. The
2422 &%-bS%& option is used for reading in a number of messages in batched SMTP
2426 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2427 &%-oee%& options were present before any other options, for compatibility with
2428 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2431 .cindex "queue runner"
2432 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2433 were present before any other options, for compatibility with Smail. The &%-q%&
2434 option causes a single queue runner process to be started.
2436 .cindex "&'newaliases'&"
2437 .cindex "alias file" "building"
2438 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2439 If Exim is called under the name &'newaliases'& it behaves as if the option
2440 &%-bi%& were present before any other options, for compatibility with Sendmail.
2441 This option is used for rebuilding Sendmail's alias file. Exim does not have
2442 the concept of a single alias file, but can be configured to run a given
2443 command if called with the &%-bi%& option.
2446 .section "Trusted and admin users" "SECTtrustedadmin"
2447 Some Exim options are available only to &'trusted users'& and others are
2448 available only to &'admin users'&. In the description below, the phrases &"Exim
2449 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2450 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2451 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2454 .cindex "trusted user" "definition of"
2455 .cindex "user" "trusted definition of"
2456 The trusted users are root, the Exim user, any user listed in the
2457 &%trusted_users%& configuration option, and any user whose current group or any
2458 supplementary group is one of those listed in the &%trusted_groups%&
2459 configuration option. Note that the Exim group is not automatically trusted.
2461 .cindex '&"From"& line'
2462 .cindex "envelope sender"
2463 Trusted users are always permitted to use the &%-f%& option or a leading
2464 &"From&~"& line to specify the envelope sender of a message that is passed to
2465 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2466 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2467 users to set envelope senders.
2469 .cindex "&'From:'& header line"
2470 .cindex "&'Sender:'& header line"
2471 For a trusted user, there is never any check on the contents of the &'From:'&
2472 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2473 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2475 Trusted users may also specify a host name, host address, interface address,
2476 protocol name, ident value, and authentication data when submitting a message
2477 locally. Thus, they are able to insert messages into Exim's queue locally that
2478 have the characteristics of messages received from a remote host. Untrusted
2479 users may in some circumstances use &%-f%&, but can never set the other values
2480 that are available to trusted users.
2482 .cindex "user" "admin definition of"
2483 .cindex "admin user" "definition of"
2484 The admin users are root, the Exim user, and any user that is a member of the
2485 Exim group or of any group listed in the &%admin_groups%& configuration option.
2486 The current group does not have to be one of these groups.
2488 Admin users are permitted to list the queue, and to carry out certain
2489 operations on messages, for example, to force delivery failures. It is also
2490 necessary to be an admin user in order to see the full information provided by
2491 the Exim monitor, and full debugging output.
2493 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2494 Exim to attempt delivery of messages on its queue is restricted to admin users.
2495 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2496 option false (that is, specifying &%no_prod_requires_admin%&).
2498 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2499 is restricted to admin users unless &%queue_list_requires_admin%& is set
2504 &*Warning*&: If you configure your system so that admin users are able to
2505 edit Exim's configuration file, you are giving those users an easy way of
2506 getting root. There is further discussion of this issue at the start of chapter
2512 .section "Command line options"
2513 The command options are described in alphabetical order below.
2515 . ////////////////////////////////////////////////////////////////////////////
2516 . Insert a stylized XML comment here, to identify the start of the command line
2517 . options. This is for the benefit of the Perl script that automatically
2518 . creates a man page for the options.
2519 . ////////////////////////////////////////////////////////////////////////////
2522 <!-- === Start of command line options === -->
2529 .cindex "options" "command line; terminating"
2530 This is a pseudo-option whose only purpose is to terminate the options and
2531 therefore to cause subsequent command line items to be treated as arguments
2532 rather than options, even if they begin with hyphens.
2535 .oindex "&%--help%&"
2536 This option causes Exim to output a few sentences stating what it is.
2537 The same output is generated if the Exim binary is called with no options and
2540 .vitem &%-B%&<&'type'&>
2542 .cindex "8-bit characters"
2543 .cindex "Sendmail compatibility" "8-bit characters"
2544 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2545 clean; it ignores this option.
2550 .cindex "SMTP listener"
2551 .cindex "queue runner"
2552 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2553 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2554 that the daemon should also initiate periodic queue runs.
2556 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2557 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2558 disconnect from the controlling terminal. When running this way, it can be
2559 stopped by pressing ctrl-C.
2561 By default, Exim listens for incoming connections to the standard SMTP port on
2562 all the host's running interfaces. However, it is possible to listen on other
2563 ports, on multiple ports, and only on specific interfaces. Chapter
2564 &<<CHAPinterfaces>>& contains a description of the options that control this.
2566 When a listening daemon
2567 .cindex "daemon" "process id (pid)"
2568 .cindex "pid (process id)" "of daemon"
2569 is started without the use of &%-oX%& (that is, without overriding the normal
2570 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2571 in Exim's spool directory. This location can be overridden by setting
2572 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2575 When &%-oX%& is used on the command line to start a listening daemon, the
2576 process id is not written to the normal pid file path. However, &%-oP%& can be
2577 used to specify a path on the command line if a pid file is required.
2581 can be used to cause the daemon to re-exec itself. This should be done whenever
2582 Exim's configuration file, or any file that is incorporated into it by means of
2583 the &%.include%& facility, is changed, and also whenever a new version of Exim
2584 is installed. It is not necessary to do this when other files that are
2585 referenced from the configuration (for example, alias files) are changed,
2586 because these are reread each time they are used.
2590 This option has the same effect as &%-bd%& except that it never disconnects
2591 from the controlling terminal, even when no debugging is specified.
2595 .cindex "testing" "string expansion"
2596 .cindex "expansion" "testing"
2597 Run Exim in expansion testing mode. Exim discards its root privilege, to
2598 prevent ordinary users from using this mode to read otherwise inaccessible
2599 files. If no arguments are given, Exim runs interactively, prompting for lines
2600 of data. Otherwise, it processes each argument in turn.
2602 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2603 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2604 used without command line arguments. If successful, it uses the &[readline()]&
2605 function, which provides extensive line-editing facilities, for reading the
2606 test data. A line history is supported.
2608 Long expansion expressions can be split over several lines by using backslash
2609 continuations. As in Exim's run time configuration, white space at the start of
2610 continuation lines is ignored. Each argument or data line is passed through the
2611 string expansion mechanism, and the result is output. Variable values from the
2612 configuration file (for example, &$qualify_domain$&) are available, but no
2613 message-specific values (such as &$domain$&) are set, because no message is
2616 &*Note*&: If you use this mechanism to test lookups, and you change the data
2617 files or databases you are using, you must exit and restart Exim before trying
2618 the same lookup again. Otherwise, because each Exim process caches the results
2619 of lookups, you will just get the same result as before.
2621 .vitem &%-bF%&&~<&'filename'&>
2623 .cindex "system filter" "testing"
2624 .cindex "testing" "system filter"
2625 This option is the same as &%-bf%& except that it assumes that the filter being
2626 tested is a system filter. The additional commands that are available only in
2627 system filters are recognized.
2629 .vitem &%-bf%&&~<&'filename'&>
2631 .cindex "filter" "testing"
2632 .cindex "testing" "filter file"
2633 .cindex "forward file" "testing"
2634 .cindex "testing" "forward file"
2635 .cindex "Sieve filter" "testing"
2636 This option runs Exim in user filter testing mode; the file is the filter file
2637 to be tested, and a test message must be supplied on the standard input. If
2638 there are no message-dependent tests in the filter, an empty file can be
2641 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2642 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2643 filter and a user filter in the same run. For example:
2645 exim -bF /system/filter -bf /user/filter </test/message
2647 This is helpful when the system filter adds header lines or sets filter
2648 variables that are used by the user filter.
2650 If the test filter file does not begin with one of the special lines
2655 it is taken to be a normal &_.forward_& file, and is tested for validity under
2656 that interpretation. See sections &<<SECTitenonfilred>>& to
2657 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2660 The result of an Exim command that uses &%-bf%&, provided no errors are
2661 detected, is a list of the actions that Exim would try to take if presented
2662 with the message for real. More details of filter testing are given in the
2663 separate document entitled &'Exim's interfaces to mail filtering'&.
2665 When testing a filter file,
2666 .cindex "&""From""& line"
2667 .cindex "envelope sender"
2668 .cindex "&%-f%& option" "for filter testing"
2669 the envelope sender can be set by the &%-f%& option,
2670 or by a &"From&~"& line at the start of the test message. Various parameters
2671 that would normally be taken from the envelope recipient address of the message
2672 can be set by means of additional command line options (see the next four
2675 .vitem &%-bfd%&&~<&'domain'&>
2677 .cindex "&$qualify_domain$&"
2678 This sets the domain of the recipient address when a filter file is being
2679 tested by means of the &%-bf%& option. The default is the value of
2682 .vitem &%-bfl%&&~<&'local&~part'&>
2684 This sets the local part of the recipient address when a filter file is being
2685 tested by means of the &%-bf%& option. The default is the username of the
2686 process that calls Exim. A local part should be specified with any prefix or
2687 suffix stripped, because that is how it appears to the filter when a message is
2688 actually being delivered.
2690 .vitem &%-bfp%&&~<&'prefix'&>
2692 This sets the prefix of the local part of the recipient address when a filter
2693 file is being tested by means of the &%-bf%& option. The default is an empty
2696 .vitem &%-bfs%&&~<&'suffix'&>
2698 This sets the suffix of the local part of the recipient address when a filter
2699 file is being tested by means of the &%-bf%& option. The default is an empty
2702 .vitem &%-bh%&&~<&'IP&~address'&>
2704 .cindex "testing" "incoming SMTP"
2705 .cindex "SMTP" "testing incoming"
2706 .cindex "testing" "relay control"
2707 .cindex "relaying" "testing configuration"
2708 .cindex "policy control" "testing"
2709 .cindex "debugging" "&%-bh%& option"
2710 This option runs a fake SMTP session as if from the given IP address, using the
2711 standard input and output. The IP address may include a port number at the end,
2712 after a full stop. For example:
2714 exim -bh 10.9.8.7.1234
2715 exim -bh fe80::a00:20ff:fe86:a061.5678
2717 When an IPv6 address is given, it is converted into canonical form. In the case
2718 of the second example above, the value of &$sender_host_address$& after
2719 conversion to the canonical form is
2720 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2722 Comments as to what is going on are written to the standard error file. These
2723 include lines beginning with &"LOG"& for anything that would have been logged.
2724 This facility is provided for testing configuration options for incoming
2725 messages, to make sure they implement the required policy. For example, you can
2726 test your relay controls using &%-bh%&.
2730 You cannot test features of the configuration that rely on
2731 ident (RFC 1413) callouts. These cannot be done when testing using
2732 &%-bh%& because there is no incoming SMTP connection.
2734 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2735 are also skipped when testing using &%-bh%&. If you want these callouts to
2736 occur, use &%-bhc%& instead.
2738 Messages supplied during the testing session are discarded, and nothing is
2739 written to any of the real log files. There may be pauses when DNS (and other)
2740 lookups are taking place, and of course these may time out. The &%-oMi%& option
2741 can be used to specify a specific IP interface and port if this is important.
2743 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2744 output just states whether a given recipient address from a given host is
2745 acceptable or not. See section &<<SECTcheckaccess>>&.
2747 .vitem &%-bhc%&&~<&'IP&~address'&>
2749 This option operates in the same way as &%-bh%&, except that address
2750 verification callouts are performed if required. This includes consulting and
2751 updating the callout cache database.
2755 .cindex "alias file" "building"
2756 .cindex "building alias file"
2757 .cindex "Sendmail compatibility" "&%-bi%& option"
2758 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2759 Exim does not have the concept of a single alias file, and so it cannot mimic
2760 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2761 tend to appear in various scripts such as NIS make files, so the option must be
2764 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2765 configuration option is run, under the uid and gid of the caller of Exim. If
2766 the &%-oA%& option is used, its value is passed to the command as an argument.
2767 The command set by &%bi_command%& may not contain arguments. The command can
2768 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2769 if this is required. If the &%bi_command%& option is not set, calling Exim with
2774 .cindex "local message reception"
2775 This option runs an Exim receiving process that accepts an incoming,
2776 locally-generated message on the current input. The recipients are given as the
2777 command arguments (except when &%-t%& is also present &-- see below). Each
2778 argument can be a comma-separated list of RFC 2822 addresses. This is the
2779 default option for selecting the overall action of an Exim call; it is assumed
2780 if no other conflicting option is present.
2782 If any addresses in the message are unqualified (have no domain), they are
2783 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
2784 options, as appropriate. The &%-bnq%& option (see below) provides a way of
2785 suppressing this for special cases.
2787 Policy checks on the contents of local messages can be enforced by means of
2788 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
2790 .cindex "return code" "for &%-bm%&"
2791 The return code is zero if the message is successfully accepted. Otherwise, the
2792 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
2795 .cindex "message" "format"
2796 .cindex "format" "message"
2797 .cindex "&""From""& line"
2798 .cindex "UUCP" "&""From""& line"
2799 .cindex "Sendmail compatibility" "&""From""& line"
2800 of the message must be as defined in RFC 2822, except that, for
2801 compatibility with Sendmail and Smail, a line in one of the forms
2803 From sender Fri Jan 5 12:55 GMT 1997
2804 From sender Fri, 5 Jan 97 12:55:01
2806 (with the weekday optional, and possibly with additional text after the date)
2807 is permitted to appear at the start of the message. There appears to be no
2808 authoritative specification of the format of this line. Exim recognizes it by
2809 matching against the regular expression defined by the &%uucp_from_pattern%&
2810 option, which can be changed if necessary.
2813 .cindex "&%-f%& option" "overriding &""From""& line"
2814 specified sender is treated as if it were given as the argument to the
2815 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
2816 preference to the address taken from the message. The caller of Exim must be a
2817 trusted user for the sender of a message to be set in this way.
2821 .cindex "address qualification" "suppressing"
2822 By default, Exim automatically qualifies unqualified addresses (those
2823 without domains) that appear in messages that are submitted locally (that
2824 is, not over TCP/IP). This qualification applies both to addresses in
2825 envelopes, and addresses in header lines. Sender addresses are qualified using
2826 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
2827 defaults to the value of &%qualify_domain%&).
2829 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
2830 being used to re-submit messages that originally came from remote hosts after
2831 content scanning, you probably do not want to qualify unqualified addresses in
2832 header lines. (Such lines will be present only if you have not enabled a header
2833 syntax check in the appropriate ACL.)
2835 The &%-bnq%& option suppresses all qualification of unqualified addresses in
2836 messages that originate on the local host. When this is used, unqualified
2837 addresses in the envelope provoke errors (causing message rejection) and
2838 unqualified addresses in header lines are left alone.
2843 .cindex "configuration options" "extracting"
2844 .cindex "options" "configuration &-- extracting"
2845 If this option is given with no arguments, it causes the values of all Exim's
2846 main configuration options to be written to the standard output. The values
2847 of one or more specific options can be requested by giving their names as
2848 arguments, for example:
2850 exim -bP qualify_domain hold_domains
2852 However, any option setting that is preceded by the word &"hide"& in the
2853 configuration file is not shown in full, except to an admin user. For other
2854 users, the output is as in this example:
2856 mysql_servers = <value not displayable>
2858 If &%configure_file%& is given as an argument, the name of the run time
2859 configuration file is output.
2860 If a list of configuration files was supplied, the value that is output here
2861 is the name of the file that was actually used.
2863 .cindex "daemon" "process id (pid)"
2864 .cindex "pid (process id)" "of daemon"
2865 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
2866 directories where log files and daemon pid files are written are output,
2867 respectively. If these values are unset, log files are written in a
2868 sub-directory of the spool directory called &%log%&, and the pid file is
2869 written directly into the spool directory.
2871 If &%-bP%& is followed by a name preceded by &`+`&, for example,
2873 exim -bP +local_domains
2875 it searches for a matching named list of any type (domain, host, address, or
2876 local part) and outputs what it finds.
2878 .cindex "options" "router &-- extracting"
2879 .cindex "options" "transport &-- extracting"
2880 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
2881 followed by the name of an appropriate driver instance, the option settings for
2882 that driver are output. For example:
2884 exim -bP transport local_delivery
2886 The generic driver options are output first, followed by the driver's private
2887 options. A list of the names of drivers of a particular type can be obtained by
2888 using one of the words &%router_list%&, &%transport_list%&, or
2889 &%authenticator_list%&, and a complete list of all drivers with their option
2890 settings can be obtained by using &%routers%&, &%transports%&, or
2896 .cindex "queue" "listing messages on"
2897 .cindex "listing" "messages on the queue"
2898 This option requests a listing of the contents of the mail queue on the
2899 standard output. If the &%-bp%& option is followed by a list of message ids,
2900 just those messages are listed. By default, this option can be used only by an
2901 admin user. However, the &%queue_list_requires_admin%& option can be set false
2902 to allow any user to see the queue.
2904 Each message on the queue is displayed as in the following example:
2906 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
2907 red.king@looking-glass.fict.example
2910 .cindex "message" "size in queue listing"
2911 .cindex "size" "of message"
2912 The first line contains the length of time the message has been on the queue
2913 (in this case 25 minutes), the size of the message (2.9K), the unique local
2914 identifier for the message, and the message sender, as contained in the
2915 envelope. For bounce messages, the sender address is empty, and appears as
2916 &"<>"&. If the message was submitted locally by an untrusted user who overrode
2917 the default sender address, the user's login name is shown in parentheses
2918 before the sender address.
2920 .cindex "frozen messages" "in queue listing"
2921 If the message is frozen (attempts to deliver it are suspended) then the text
2922 &"*** frozen ***"& is displayed at the end of this line.
2924 The recipients of the message (taken from the envelope, not the headers) are
2925 displayed on subsequent lines. Those addresses to which the message has already
2926 been delivered are marked with the letter D. If an original address gets
2927 expanded into several addresses via an alias or forward file, the original is
2928 displayed with a D only when deliveries for all of its child addresses are
2934 This option operates like &%-bp%&, but in addition it shows delivered addresses
2935 that were generated from the original top level address(es) in each message by
2936 alias or forwarding operations. These addresses are flagged with &"+D"& instead
2942 .cindex "queue" "count of messages on"
2943 This option counts the number of messages on the queue, and writes the total
2944 to the standard output. It is restricted to admin users, unless
2945 &%queue_list_requires_admin%& is set false.
2950 This option operates like &%-bp%&, but the output is not sorted into
2951 chronological order of message arrival. This can speed it up when there are
2952 lots of messages on the queue, and is particularly useful if the output is
2953 going to be post-processed in a way that doesn't need the sorting.
2957 This option is a combination of &%-bpr%& and &%-bpa%&.
2961 This option is a combination of &%-bpr%& and &%-bpu%&.
2966 This option operates like &%-bp%& but shows only undelivered top-level
2967 addresses for each message displayed. Addresses generated by aliasing or
2968 forwarding are not shown, unless the message was deferred after processing by a
2969 router with the &%one_time%& option set.
2974 .cindex "testing" "retry configuration"
2975 .cindex "retry" "configuration testing"
2976 This option is for testing retry rules, and it must be followed by up to three
2977 arguments. It causes Exim to look for a retry rule that matches the values
2978 and to write it to the standard output. For example:
2980 exim -brt bach.comp.mus.example
2981 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
2984 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
2985 argument, which is required, can be a complete address in the form
2986 &'local_part@domain'&, or it can be just a domain name. If the second argument
2987 contains a dot, it is interpreted as an optional second domain name; if no
2988 retry rule is found for the first argument, the second is tried. This ties in
2989 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
2990 rule is found that matches the host, one that matches the mail domain is
2991 sought. Finally, an argument that is the name of a specific delivery error, as
2992 used in setting up retry rules, can be given. For example:
2994 exim -brt haydn.comp.mus.example quota_3d
2995 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3001 .cindex "testing" "rewriting"
3002 .cindex "rewriting" "testing"
3003 This option is for testing address rewriting rules, and it must be followed by
3004 a single argument, consisting of either a local part without a domain, or a
3005 complete address with a fully qualified domain. Exim outputs how this address
3006 would be rewritten for each possible place it might appear. See chapter
3007 &<<CHAPrewrite>>& for further details.
3011 .cindex "SMTP" "batched incoming"
3012 .cindex "batched SMTP input"
3013 This option is used for batched SMTP input, which is an alternative interface
3014 for non-interactive local message submission. A number of messages can be
3015 submitted in a single run. However, despite its name, this is not really SMTP
3016 input. Exim reads each message's envelope from SMTP commands on the standard
3017 input, but generates no responses. If the caller is trusted, or
3018 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3019 believed; otherwise the sender is always the caller of Exim.
3021 The message itself is read from the standard input, in SMTP format (leading
3022 dots doubled), terminated by a line containing just a single dot. An error is
3023 provoked if the terminating dot is missing. A further message may then follow.
3025 As for other local message submissions, the contents of incoming batch SMTP
3026 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3027 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3028 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3030 Some other SMTP commands are recognized in the input. HELO and EHLO act
3031 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3032 QUIT quits, ignoring the rest of the standard input.
3034 .cindex "return code" "for &%-bS%&"
3035 If any error is encountered, reports are written to the standard output and
3036 error streams, and Exim gives up immediately. The return code is 0 if no error
3037 was detected; it is 1 if one or more messages were accepted before the error
3038 was detected; otherwise it is 2.
3040 More details of input using batched SMTP are given in section
3041 &<<SECTincomingbatchedSMTP>>&.
3045 .cindex "SMTP" "local input"
3046 .cindex "local SMTP input"
3047 This option causes Exim to accept one or more messages by reading SMTP commands
3048 on the standard input, and producing SMTP replies on the standard output. SMTP
3049 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3050 Some user agents use this interface as a way of passing locally-generated
3051 messages to the MTA.
3054 .cindex "sender" "source of"
3055 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3056 set, the senders of messages are taken from the SMTP MAIL commands.
3057 Otherwise the content of these commands is ignored and the sender is set up as
3058 the calling user. Unqualified addresses are automatically qualified using
3059 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3060 &%-bnq%& option is used.
3064 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3065 using a listening daemon. Exim can distinguish the two cases by checking
3066 whether the standard input is a TCP/IP socket. When Exim is called from
3067 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3068 above concerning senders and qualification do not apply. In this situation,
3069 Exim behaves in exactly the same way as it does when receiving a message via
3070 the listening daemon.
3074 .cindex "testing" "addresses"
3075 .cindex "address" "testing"
3076 This option runs Exim in address testing mode, in which each argument is taken
3077 as an address to be tested for deliverability. The results are written to the
3078 standard output. If a test fails, and the caller is not an admin user, no
3079 details of the failure are output, because these might contain sensitive
3080 information such as usernames and passwords for database lookups.
3082 If no arguments are given, Exim runs in an interactive manner, prompting with a
3083 right angle bracket for addresses to be tested.
3085 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3086 &[readline()]& function, because it is running as &'root'& and there are
3089 Each address is handled as if it were the recipient address of a message
3090 (compare the &%-bv%& option). It is passed to the routers and the result is
3091 written to the standard output. However, any router that has
3092 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3093 genuine routing tests if your first router passes everything to a scanner
3097 .cindex "return code" "for &%-bt%&"
3098 return code is 2 if any address failed outright; it is 1 if no address
3099 failed outright but at least one could not be resolved for some reason. Return
3100 code 0 is given only when all addresses succeed.
3102 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3103 routers in the configuration makes any tests on the sender address of a
3105 .cindex "&%-f%& option" "for address testing"
3106 you can use the &%-f%& option to set an appropriate sender when running
3107 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3108 default qualifying domain. However, if you have set up (for example) routers
3109 whose behaviour depends on the contents of an incoming message, you cannot test
3110 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3115 .cindex "version number of Exim" "verifying"
3116 This option causes Exim to write the current version number, compilation
3117 number, and compilation date of the &'exim'& binary to the standard output.
3118 It also lists the DBM library this is being used, the optional modules (such as
3119 specific lookup types), the drivers that are included in the binary, and the
3120 name of the run time configuration file that is in use.
3122 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3123 configuration file. However, this is a static check only. It cannot check
3124 values that are to be expanded. For example, although a misspelt ACL verb is
3125 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3126 alone to discover (for example) all the typos in the configuration; some
3127 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3128 dynamic testing facilities.
3132 .cindex "verifying address" "using &%-bv%&"
3133 .cindex "address" "verification"
3134 This option runs Exim in address verification mode, in which each argument is
3135 taken as an address to be verified. During normal operation, verification
3136 happens mostly as a consequence processing a &%verify%& condition in an ACL
3137 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, see the &%-bh%&
3140 If verification fails, and the caller is not an admin user, no details of the
3141 failure are output, because these might contain sensitive information such as
3142 usernames and passwords for database lookups.
3144 If no arguments are given, Exim runs in an interactive manner, prompting with a
3145 right angle bracket for addresses to be verified.
3147 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3148 &[readline()]& function, because it is running as &'exim'& and there are
3151 Verification differs from address testing (the &%-bt%& option) in that routers
3152 that have &%no_verify%& set are skipped, and if the address is accepted by a
3153 router that has &%fail_verify%& set, verification fails. The address is
3154 verified as a recipient if &%-bv%& is used; to test verification for a sender
3155 address, &%-bvs%& should be used.
3157 If the &%-v%& option is not set, the output consists of a single line for each
3158 address, stating whether it was verified or not, and giving a reason in the
3159 latter case. Otherwise, more details are given of how the address has been
3160 handled, and in the case of address redirection, all the generated addresses
3161 are also considered. Without &%-v%&, generating more than one address by
3162 redirection causes verification to end successfully.
3165 .cindex "return code" "for &%-bv%&"
3166 return code is 2 if any address failed outright; it is 1 if no address
3167 failed outright but at least one could not be resolved for some reason. Return
3168 code 0 is given only when all addresses succeed.
3170 If any of the routers in the configuration makes any tests on the sender
3171 address of a message, you should use the &%-f%& option to set an appropriate
3172 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3173 calling user at the default qualifying domain.
3177 This option acts like &%-bv%&, but verifies the address as a sender rather
3178 than a recipient address. This affects any rewriting and qualification that
3181 .vitem &%-C%&&~<&'filelist'&>
3183 .cindex "configuration file" "alternate"
3184 .cindex "CONFIGURE_FILE"
3185 .cindex "alternate configuration file"
3186 This option causes Exim to find the run time configuration file from the given
3187 list instead of from the list specified by the CONFIGURE_FILE
3188 compile-time setting. Usually, the list will consist of just a single file
3189 name, but it can be a colon-separated list of names. In this case, the first
3190 file that exists is used. Failure to open an existing file stops Exim from
3191 proceeding any further along the list, and an error is generated.
3193 When this option is used by a caller other than root or the Exim user, and the
3194 list is different from the compiled-in list, Exim gives up its root privilege
3195 immediately, and runs with the real and effective uid and gid set to those of
3196 the caller. However, if ALT_CONFIG_ROOT_ONLY is defined in
3197 &_Local/Makefile_&, root privilege is retained for &%-C%& only if the caller of
3200 That is, the Exim user is no longer privileged in this regard. This build-time
3201 option is not set by default in the Exim source distribution tarbundle.
3202 However, if you are using a &"packaged"& version of Exim (source or binary),
3203 the packagers might have enabled it.
3205 Setting ALT_CONFIG_ROOT_ONLY locks out the possibility of testing a
3206 configuration using &%-C%& right through message reception and delivery, even
3207 if the caller is root. The reception works, but by that time, Exim is running
3208 as the Exim user, so when it re-executes to regain privilege for the delivery,
3209 the use of &%-C%& causes privilege to be lost. However, root can test reception
3210 and delivery using two separate commands (one to put a message on the queue,
3211 using &%-odq%&, and another to do the delivery, using &%-M%&).
3213 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3214 prefix string with which any file named in a &%-C%& command line option
3215 must start. In addition, the file name must not contain the sequence &`/../`&.
3216 However, if the value of the &%-C%& option is identical to the value of
3217 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3218 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3219 unset, any file name can be used with &%-C%&.
3221 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3222 to a directory to which only root has access. This prevents someone who has
3223 broken into the Exim account from running a privileged Exim with an arbitrary
3226 The &%-C%& facility is useful for ensuring that configuration files are
3227 syntactically correct, but cannot be used for test deliveries, unless the
3228 caller is privileged, or unless it is an exotic configuration that does not
3229 require privilege. No check is made on the owner or group of the files
3230 specified by this option.
3232 .vitem &%-D%&<&'macro'&>=<&'value'&>
3234 .cindex "macro" "setting on command line"
3235 This option can be used to override macro definitions in the configuration file
3236 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3237 unprivileged caller, it causes Exim to give up its root privilege.
3238 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3239 completely disabled, and its use causes an immediate error exit.
3241 The entire option (including equals sign if present) must all be within one
3242 command line item. &%-D%& can be used to set the value of a macro to the empty
3243 string, in which case the equals sign is optional. These two commands are
3249 To include spaces in a macro definition item, quotes must be used. If you use
3250 quotes, spaces are permitted around the macro name and the equals sign. For
3253 exim '-D ABC = something' ...
3255 &%-D%& may be repeated up to 10 times on a command line.
3257 .vitem &%-d%&<&'debug&~options'&>
3259 .cindex "debugging" "list of selectors"
3260 .cindex "debugging" "&%-d%& option"
3261 This option causes debugging information to be written to the standard
3262 error stream. It is restricted to admin users because debugging output may show
3263 database queries that contain password information. Also, the details of users'
3264 filter files should be protected. When &%-d%& is used, &%-v%& is assumed. If
3265 &%-d%& is given on its own, a lot of standard debugging data is output. This
3266 can be reduced, or increased to include some more rarely needed information, by
3267 directly following &%-d%& with a string made up of names preceded by plus or
3268 minus characters. These add or remove sets of debugging data, respectively. For
3269 example, &%-d+filter%& adds filter debugging, whereas &%-d-all+filter%& selects
3270 only filter debugging. Note that no spaces are allowed in the debug setting.
3271 The available debugging categories are:
3273 &`acl `& ACL interpretation
3274 &`auth `& authenticators
3275 &`deliver `& general delivery logic
3276 &`dns `& DNS lookups (see also resolver)
3277 &`dnsbl `& DNS black list (aka RBL) code
3278 &`exec `& arguments for &[execv()]& calls
3279 &`expand `& detailed debugging for string expansions
3280 &`filter `& filter handling
3281 &`hints_lookup `& hints data lookups
3282 &`host_lookup `& all types of name-to-IP address handling
3283 &`ident `& ident lookup
3284 &`interface `& lists of local interfaces
3285 &`lists `& matching things in lists
3286 &`load `& system load checks
3287 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3288 &<<CHAPlocalscan>>&)
3289 &`lookup `& general lookup code and all lookups
3290 &`memory `& memory handling
3291 &`pid `& add pid to debug output lines
3292 &`process_info `& setting info for the process log
3293 &`queue_run `& queue runs
3294 &`receive `& general message reception logic
3295 &`resolver `& turn on the DNS resolver's debugging output
3296 &`retry `& retry handling
3297 &`rewrite `& address rewriting
3298 &`route `& address routing
3299 &`timestamp `& add timestamp to debug output lines
3301 &`transport `& transports
3302 &`uid `& changes of uid/gid and looking up uid/gid
3303 &`verify `& address verification logic
3304 &`all `& almost all of the above (see below), and also &%-v%&
3306 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3307 for &`-all`&. The reason for this is that &`+all`& is something that people
3308 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3309 is included, an awful lot of output that is very rarely of interest is
3310 generated, so it now has to be explicitly requested. However, &`-all`& does
3311 turn everything off.
3313 .cindex "resolver" "debugging output"
3314 .cindex "DNS resolver" "debugging output"
3315 The &`resolver`& option produces output only if the DNS resolver was compiled
3316 with DEBUG enabled. This is not the case in some operating systems. Also,
3317 unfortunately, debugging output from the DNS resolver is written to stdout
3320 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3321 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3322 However, the &`pid`& selector is forced when debugging is turned on for a
3323 daemon, which then passes it on to any re-executed Exims. Exim also
3324 automatically adds the pid to debug lines when several remote deliveries are
3327 The &`timestamp`& selector causes the current time to be inserted at the start
3328 of all debug output lines. This can be useful when trying to track down delays
3331 If the &%debug_print%& option is set in any driver, it produces output whenever
3332 any debugging is selected, or if &%-v%& is used.
3334 .vitem &%-dd%&<&'debug&~options'&>
3336 This option behaves exactly like &%-d%& except when used on a command that
3337 starts a daemon process. In that case, debugging is turned off for the
3338 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3339 behaviour of the daemon without creating as much output as full debugging does.
3342 .oindex "&%-dropcr%&"
3343 This is an obsolete option that is now a no-op. It used to affect the way Exim
3344 handled CR and LF characters in incoming messages. What happens now is
3345 described in section &<<SECTlineendings>>&.
3349 .cindex "bounce message" "generating"
3350 This option specifies that an incoming message is a locally-generated delivery
3351 failure report. It is used internally by Exim when handling delivery failures
3352 and is not intended for external use. Its only effect is to stop Exim
3353 generating certain messages to the postmaster, as otherwise message cascades
3354 could occur in some situations. As part of the same option, a message id may
3355 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3356 new message contains the id, following &"R="&, as a cross-reference.
3359 .oindex "&%-e%&&'x'&"
3360 There are a number of Sendmail options starting with &%-oe%& which seem to be
3361 called by various programs without the leading &%o%& in the option. For
3362 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3363 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3365 .vitem &%-F%&&~<&'string'&>
3367 .cindex "sender" "name"
3368 .cindex "name" "of sender"
3369 This option sets the sender's full name for use when a locally-generated
3370 message is being accepted. In the absence of this option, the user's &'gecos'&
3371 entry from the password data is used. As users are generally permitted to alter
3372 their &'gecos'& entries, no security considerations are involved. White space
3373 between &%-F%& and the <&'string'&> is optional.
3375 .vitem &%-f%&&~<&'address'&>
3377 .cindex "sender" "address"
3378 .cindex "address" "sender"
3379 .cindex "trusted user"
3380 .cindex "envelope sender"
3381 .cindex "user" "trusted"
3382 This option sets the address of the envelope sender of a locally-generated
3383 message (also known as the return path). The option can normally be used only
3384 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3387 Processes running as root or the Exim user are always trusted. Other
3388 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3389 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3390 of a local message is set to the caller's login name at the default qualify
3393 There is one exception to the restriction on the use of &%-f%&: an empty sender
3394 can be specified by any user, trusted or not, to create a message that can
3395 never provoke a bounce. An empty sender can be specified either as an empty
3396 string, or as a pair of angle brackets with nothing between them, as in these
3397 examples of shell commands:
3399 exim -f '<>' user@domain
3400 exim -f "" user@domain
3402 In addition, the use of &%-f%& is not restricted when testing a filter file
3403 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3406 Allowing untrusted users to change the sender address does not of itself make
3407 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3408 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3409 though this can be overridden by setting &%no_local_from_check%&.
3412 .cindex "&""From""& line"
3413 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3414 given as two arguments or one combined argument). The sender of a
3415 locally-generated message can also be set (when permitted) by an initial
3416 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3417 if &%-f%& is also present, it overrides &"From&~"&.
3421 .cindex "Sendmail compatibility" "&%-G%& option ignored"
3422 This is a Sendmail option which is ignored by Exim.
3424 .vitem &%-h%&&~<&'number'&>
3426 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3427 This option is accepted for compatibility with Sendmail, but has no effect. (In
3428 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3433 .cindex "Solaris" "&'mail'& command"
3434 .cindex "dot in incoming" "non-SMTP message"
3435 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3436 line by itself should not terminate an incoming, non-SMTP message. I can find
3437 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3438 command in Solaris 2.4 uses it. See also &%-ti%&.
3440 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3442 .cindex "forcing delivery"
3443 .cindex "delivery" "forcing attempt"
3444 .cindex "frozen messages" "forcing delivery"
3445 This option requests Exim to run a delivery attempt on each message in turn. If
3446 any of the messages are frozen, they are automatically thawed before the
3447 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3448 and &%hold_domains%& are ignored.
3451 .cindex "hints database" "overriding retry hints"
3452 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3453 the normal retry time has not yet been reached. This option requires the caller
3454 to be an admin user. However, there is an option called &%prod_requires_admin%&
3455 which can be set false to relax this restriction (and also the same requirement
3456 for the &%-q%&, &%-R%&, and &%-S%& options).
3458 The deliveries happen synchronously, that is, the original Exim process does
3459 not terminate until all the delivery attempts have finished. No output is
3460 produced unless there is a serious error. If you want to see what is happening,
3461 use the &%-v%& option as well, or inspect Exim's main log.
3463 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3465 .cindex "message" "adding recipients"
3466 .cindex "recipient" "adding"
3467 This option requests Exim to add the addresses to the list of recipients of the
3468 message (&"ar"& for &"add recipients"&). The first argument must be a message
3469 id, and the remaining ones must be email addresses. However, if the message is
3470 active (in the middle of a delivery attempt), it is not altered. This option
3471 can be used only by an admin user.
3473 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3474 &~<&'message&~id'&>"
3476 .cindex "SMTP" "passed connection"
3477 .cindex "SMTP" "multiple deliveries"
3478 .cindex "multiple SMTP deliveries"
3479 This option is not intended for use by external callers. It is used internally
3480 by Exim to invoke another instance of itself to deliver a waiting message using
3481 an existing SMTP connection, which is passed as the standard input. Details are
3482 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3483 must be root or the Exim user in order to use it.
3487 This option is not intended for use by external callers. It is used internally
3488 by Exim in conjunction with the &%-MC%& option. It signifies that the
3489 connection to the remote host has been authenticated.
3493 This option is not intended for use by external callers. It is used internally
3494 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3495 which Exim is connected supports pipelining.
3497 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3499 This option is not intended for use by external callers. It is used internally
3500 by Exim in conjunction with the &%-MC%& option when the original delivery was
3501 started by a queue runner. It passes on the process id of the queue runner,
3502 together with the file descriptor number of an open pipe. Closure of the pipe
3503 signals the final completion of the sequence of processes that are passing
3504 messages through the same SMTP connection.
3508 This option is not intended for use by external callers. It is used internally
3509 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3510 SMTP SIZE option should be used on messages delivered down the existing
3515 This option is not intended for use by external callers. It is used internally
3516 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3517 host to which Exim is connected supports TLS encryption.
3519 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3521 .cindex "hints database" "not overridden by &%-Mc%&"
3522 .cindex "delivery" "manually started &-- not forced"
3523 This option requests Exim to run a delivery attempt on each message in turn,
3524 but unlike the &%-M%& option, it does check for retry hints, and respects any
3525 that are found. This option is not very useful to external callers. It is
3526 provided mainly for internal use by Exim when it needs to re-invoke itself in
3527 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3528 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3529 respects retry times and other options such as &%hold_domains%& that are
3530 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3531 If you want to run a specific delivery as if in a queue run, you should use
3532 &%-q%& with a message id argument. A distinction between queue run deliveries
3533 and other deliveries is made in one or two places.
3535 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3537 .cindex "message" "changing sender"
3538 .cindex "sender" "changing"
3539 This option requests Exim to change the sender address in the message to the
3540 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3541 &"edit sender"&). There must be exactly two arguments. The first argument must
3542 be a message id, and the second one an email address. However, if the message
3543 is active (in the middle of a delivery attempt), its status is not altered.
3544 This option can be used only by an admin user.
3546 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3548 .cindex "freezing messages"
3549 .cindex "message" "manually freezing"
3550 This option requests Exim to mark each listed message as &"frozen"&. This
3551 prevents any delivery attempts taking place until the message is &"thawed"&,
3552 either manually or as a result of the &%auto_thaw%& configuration option.
3553 However, if any of the messages are active (in the middle of a delivery
3554 attempt), their status is not altered. This option can be used only by an admin
3557 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3559 .cindex "giving up on messages"
3560 .cindex "message" "abandoning delivery attempts"
3561 .cindex "delivery" "abandoning further attempts"
3562 This option requests Exim to give up trying to deliver the listed messages,
3563 including any that are frozen. However, if any of the messages are active,
3564 their status is not altered. For non-bounce messages, a delivery error message
3565 is sent to the sender, containing the text &"cancelled by administrator"&.
3566 Bounce messages are just discarded. This option can be used only by an admin
3569 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3571 .cindex "delivery" "cancelling all"
3572 This option requests Exim to mark all the recipient addresses in the messages
3573 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3574 message is active (in the middle of a delivery attempt), its status is not
3575 altered. This option can be used only by an admin user.
3577 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3579 .cindex "delivery" "cancelling by address"
3580 .cindex "recipient" "removing"
3581 .cindex "removing recipients"
3582 This option requests Exim to mark the given addresses as already delivered
3583 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3584 the remaining ones must be email addresses. These are matched to recipient
3585 addresses in the message in a case-sensitive manner. If the message is active
3586 (in the middle of a delivery attempt), its status is not altered. This option
3587 can be used only by an admin user.
3589 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3591 .cindex "removing messages"
3592 .cindex "abandoning mail"
3593 .cindex "message" "manually discarding"
3594 This option requests Exim to remove the given messages from the queue. No
3595 bounce messages are sent; each message is simply forgotten. However, if any of
3596 the messages are active, their status is not altered. This option can be used
3597 only by an admin user or by the user who originally caused the message to be
3598 placed on the queue.
3600 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3602 .cindex "thawing messages"
3603 .cindex "unfreezing messages"
3604 .cindex "frozen messages" "thawing"
3605 .cindex "message" "thawing frozen"
3606 This option requests Exim to &"thaw"& any of the listed messages that are
3607 &"frozen"&, so that delivery attempts can resume. However, if any of the
3608 messages are active, their status is not altered. This option can be used only
3611 .vitem &%-Mvb%&&~<&'message&~id'&>
3613 .cindex "listing" "message body"
3614 .cindex "message" "listing body of"
3615 This option causes the contents of the message body (-D) spool file to be
3616 written to the standard output. This option can be used only by an admin user.
3618 .vitem &%-Mvh%&&~<&'message&~id'&>
3620 .cindex "listing" "message headers"
3621 .cindex "header lines" "listing"
3622 .cindex "message" "listing header lines"
3623 This option causes the contents of the message headers (-H) spool file to be
3624 written to the standard output. This option can be used only by an admin user.
3626 .vitem &%-Mvl%&&~<&'message&~id'&>
3628 .cindex "listing" "message log"
3629 .cindex "message" "listing message log"
3630 This option causes the contents of the message log spool file to be written to
3631 the standard output. This option can be used only by an admin user.
3635 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3636 treats it that way too.
3640 .cindex "debugging" "&%-N%& option"
3641 .cindex "debugging" "suppressing delivery"
3642 This is a debugging option that inhibits delivery of a message at the transport
3643 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3644 it just doesn't actually transport the message, but instead behaves as if it
3645 had successfully done so. However, it does not make any updates to the retry
3646 database, and the log entries for deliveries are flagged with &"*>"& rather
3649 Because &%-N%& discards any message to which it applies, only root or the Exim
3650 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3651 words, an ordinary user can use it only when supplying an incoming message to
3652 which it will apply. Although transportation never fails when &%-N%& is set, an
3653 address may be deferred because of a configuration problem on a transport, or a
3654 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3655 the message, and applies to any subsequent delivery attempts that may happen
3660 .cindex "Sendmail compatibility" "&%-n%& option ignored"
3661 This option is interpreted by Sendmail to mean &"no aliasing"&. It is ignored
3664 .vitem &%-O%&&~<&'data'&>
3666 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
3669 .vitem &%-oA%&&~<&'file&~name'&>
3671 .cindex "Sendmail compatibility" "&%-oA%& option"
3672 This option is used by Sendmail in conjunction with &%-bi%& to specify an
3673 alternative alias file name. Exim handles &%-bi%& differently; see the
3676 .vitem &%-oB%&&~<&'n'&>
3678 .cindex "SMTP" "passed connection"
3679 .cindex "SMTP" "multiple deliveries"
3680 .cindex "multiple SMTP deliveries"
3681 This is a debugging option which limits the maximum number of messages that can
3682 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
3683 transport. If <&'n'&> is omitted, the limit is set to 1.
3687 .cindex "background delivery"
3688 .cindex "delivery" "in the background"
3689 This option applies to all modes in which Exim accepts incoming messages,
3690 including the listening daemon. It requests &"background"& delivery of such
3691 messages, which means that the accepting process automatically starts a
3692 delivery process for each message received, but does not wait for the delivery
3693 processes to finish.
3695 When all the messages have been received, the reception process exits,
3696 leaving the delivery processes to finish in their own time. The standard output
3697 and error streams are closed at the start of each delivery process.
3698 This is the default action if none of the &%-od%& options are present.
3700 If one of the queueing options in the configuration file
3701 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
3702 overrides it if &%queue_only_override%& is set true, which is the default
3703 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
3707 .cindex "foreground delivery"
3708 .cindex "delivery" "in the foreground"
3709 This option requests &"foreground"& (synchronous) delivery when Exim has
3710 accepted a locally-generated message. (For the daemon it is exactly the same as
3711 &%-odb%&.) A delivery process is automatically started to deliver the message,
3712 and Exim waits for it to complete before proceeding.
3714 The original Exim reception process does not finish until the delivery
3715 process for the final message has ended. The standard error stream is left open
3718 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
3719 false and one of the queueing options in the configuration file is in effect.
3721 If there is a temporary delivery error during foreground delivery, the
3722 message is left on the queue for later delivery, and the original reception
3723 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
3724 restricted configuration that never queues messages.
3729 This option is synonymous with &%-odf%&. It is provided for compatibility with
3734 .cindex "non-immediate delivery"
3735 .cindex "delivery" "suppressing immediate"
3736 .cindex "queueing incoming messages"
3737 This option applies to all modes in which Exim accepts incoming messages,
3738 including the listening daemon. It specifies that the accepting process should
3739 not automatically start a delivery process for each message received. Messages
3740 are placed on the queue, and remain there until a subsequent queue runner
3741 process encounters them. There are several configuration options (such as
3742 &%queue_only%&) that can be used to queue incoming messages under certain
3743 conditions. This option overrides all of them and also &%-odqs%&. It always
3748 .cindex "SMTP" "delaying delivery"
3749 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
3750 However, like &%-odb%& and &%-odi%&, this option has no effect if
3751 &%queue_only_override%& is false and one of the queueing options in the
3752 configuration file is in effect.
3754 When &%-odqs%& does operate, a delivery process is started for each incoming
3755 message, in the background by default, but in the foreground if &%-odi%& is
3756 also present. The recipient addresses are routed, and local deliveries are done
3757 in the normal way. However, if any SMTP deliveries are required, they are not
3758 done at this time, so the message remains on the queue until a subsequent queue
3759 runner process encounters it. Because routing was done, Exim knows which
3760 messages are waiting for which hosts, and so a number of messages for the same
3761 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
3762 configuration option has the same effect for specific domains. See also the
3767 .cindex "error" "reporting"
3768 If an error is detected while a non-SMTP message is being received (for
3769 example, a malformed address), the error is reported to the sender in a mail
3772 .cindex "return code" "for &%-oee%&"
3774 this error message is successfully sent, the Exim receiving process
3775 exits with a return code of zero. If not, the return code is 2 if the problem
3776 is that the original message has no recipients, or 1 any other error. This is
3777 the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
3781 .cindex "error" "reporting"
3782 .cindex "return code" "for &%-oem%&"
3783 This is the same as &%-oee%&, except that Exim always exits with a non-zero
3784 return code, whether or not the error message was successfully sent.
3785 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
3789 .cindex "error" "reporting"
3790 If an error is detected while a non-SMTP message is being received, the
3791 error is reported by writing a message to the standard error file (stderr).
3792 .cindex "return code" "for &%-oep%&"
3793 The return code is 1 for all errors.
3797 .cindex "error" "reporting"
3798 This option is supported for compatibility with Sendmail, but has the same
3803 .cindex "error" "reporting"
3804 This option is supported for compatibility with Sendmail, but has the same
3809 .cindex "dot in incoming" "non-SMTP message"
3810 This option, which has the same effect as &%-i%&, specifies that a dot on a
3811 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
3812 single dot does terminate, though Exim does no special processing for other
3813 lines that start with a dot. This option is set by default if Exim is called as
3814 &'rmail'&. See also &%-ti%&.
3817 .oindex "&%-oitrue%&"
3818 This option is treated as synonymous with &%-oi%&.
3820 .vitem &%-oMa%&&~<&'host&~address'&>
3822 .cindex "sender host address" "specifying for local message"
3823 A number of options starting with &%-oM%& can be used to set values associated
3824 with remote hosts on locally-submitted messages (that is, messages not received
3825 over TCP/IP). These options can be used by any caller in conjunction with the
3826 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
3827 other circumstances, they are ignored unless the caller is trusted.
3829 The &%-oMa%& option sets the sender host address. This may include a port
3830 number at the end, after a full stop (period). For example:
3832 exim -bs -oMa 10.9.8.7.1234
3834 An alternative syntax is to enclose the IP address in square brackets,
3835 followed by a colon and the port number:
3837 exim -bs -oMa [10.9.8.7]:1234
3839 The IP address is placed in the &$sender_host_address$& variable, and the
3840 port, if present, in &$sender_host_port$&.
3842 .vitem &%-oMaa%&&~<&'name'&>
3844 .cindex "authentication name" "specifying for local message"
3845 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
3846 option sets the value of &$sender_host_authenticated$& (the authenticator
3847 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
3849 .vitem &%-oMai%&&~<&'string'&>
3851 .cindex "authentication id" "specifying for local message"
3852 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
3853 option sets the value of &$authenticated_id$& (the id that was authenticated).
3854 This overrides the default value (the caller's login id) for messages from
3855 local sources. See chapter &<<CHAPSMTPAUTH>>& for a discussion of authenticated
3858 .vitem &%-oMas%&&~<&'address'&>
3860 .cindex "authentication sender" "specifying for local message"
3861 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
3862 option sets the authenticated sender value in &$authenticated_sender$&. It
3863 overrides the sender address that is created from the caller's login id for
3864 messages from local sources. See chapter &<<CHAPSMTPAUTH>>& for a discussion of
3865 authenticated senders.
3867 .vitem &%-oMi%&&~<&'interface&~address'&>
3869 .cindex "interface address" "specifying for local message"
3870 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
3871 option sets the IP interface address value. A port number may be included,
3872 using the same syntax as for &%-oMa%&. The interface address is placed in
3873 &$interface_address$& and the port number, if present, in &$interface_port$&.
3875 .vitem &%-oMr%&&~<&'protocol&~name'&>
3877 .cindex "protocol" "incoming &-- specifying for local message"
3878 .cindex "&$received_protocol$&"
3879 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
3880 option sets the received protocol value that is stored in
3881 &$received_protocol$&. However, this applies only when &%-bs%& is not used. For
3882 interactive SMTP input (&%-bs%&), the protocol is always &"local-"& followed by
3883 one of the standard SMTP protocol names (see the description of
3884 &$received_protocol$& in section &<<SECTexpvar>>&). For &%-bS%& (batch SMTP)
3885 however, the protocol can be set by &%-oMr%&.
3887 .vitem &%-oMs%&&~<&'host&~name'&>
3889 .cindex "sender host name" "specifying for local message"
3890 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
3891 option sets the sender host name in &$sender_host_name$&. When this option is
3892 present, Exim does not attempt to look up a host name from an IP address; it
3893 uses the name it is given.
3895 .vitem &%-oMt%&&~<&'ident&~string'&>
3897 .cindex "sender ident string" "specifying for local message"
3898 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
3899 option sets the sender ident value in &$sender_ident$&. The default setting for
3900 local callers is the login id of the calling process.
3904 .cindex "Sendmail compatibility" "&%-om%& option ignored"
3905 In Sendmail, this option means &"me too"&, indicating that the sender of a
3906 message should receive a copy of the message if the sender appears in an alias
3907 expansion. Exim always does this, so the option does nothing.
3911 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
3912 This option is ignored. In Sendmail it specifies &"old style headers"&,
3913 whatever that means.
3915 .vitem &%-oP%&&~<&'path'&>
3917 .cindex "pid (process id)" "of daemon"
3918 .cindex "daemon" "process id (pid)"
3919 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
3920 value. The option specifies the file to which the process id of the daemon is
3921 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
3922 without &%-bd%&, this is the only way of causing Exim to write a pid file,
3923 because in those cases, the normal pid file is not used.
3925 .vitem &%-or%&&~<&'time'&>
3927 .cindex "timeout" "for non-SMTP input"
3928 This option sets a timeout value for incoming non-SMTP messages. If it is not
3929 set, Exim will wait forever for the standard input. The value can also be set
3930 by the &%receive_timeout%& option. The format used for specifying times is
3931 described in section &<<SECTtimeformat>>&.
3933 .vitem &%-os%&&~<&'time'&>
3935 .cindex "timeout" "for SMTP input"
3936 .cindex "SMTP timeout" "input"
3937 This option sets a timeout value for incoming SMTP messages. The timeout
3938 applies to each SMTP command and block of data. The value can also be set by
3939 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
3940 for specifying times is described in section &<<SECTtimeformat>>&.
3944 This option has exactly the same effect as &%-v%&.
3946 .vitem &%-oX%&&~<&'number&~or&~string'&>
3948 .cindex "TCP/IP" "setting listening ports"
3949 .cindex "TCP/IP" "setting listening interfaces"
3950 .cindex "port" "receiving TCP/IP"
3951 This option is relevant only when the &%-bd%& (start listening daemon) option
3952 is also given. It controls which ports and interfaces the daemon uses. Details
3953 of the syntax, and how it interacts with configuration file options, are given
3954 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
3955 file is written unless &%-oP%& is also present to specify a pid file name.
3959 .cindex "Perl" "starting the interpreter"
3960 This option applies when an embedded Perl interpreter is linked with Exim (see
3961 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
3962 option, forcing the starting of the interpreter to be delayed until it is
3967 .cindex "Perl" "starting the interpreter"
3968 This option applies when an embedded Perl interpreter is linked with Exim (see
3969 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
3970 option, forcing the starting of the interpreter to occur as soon as Exim is
3973 .vitem &%-p%&<&'rval'&>:<&'sval'&>
3975 For compatibility with Sendmail, this option is equivalent to
3977 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
3979 It sets the incoming protocol and host name (for trusted callers). The
3980 host name and its colon can be omitted when only the protocol is to be set.
3981 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
3982 to embedded Perl. It is therefore impossible to set a protocol value of &`p`&
3983 or &`s`& using this option (but that does not seem a real limitation).
3987 .cindex "queue runner" "starting manually"
3988 This option is normally restricted to admin users. However, there is a
3989 configuration option called &%prod_requires_admin%& which can be set false to
3990 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
3991 and &%-S%& options).
3993 .cindex "queue runner" "description of operation"
3994 The &%-q%& option starts one queue runner process. This scans the queue of
3995 waiting messages, and runs a delivery process for each one in turn. It waits
3996 for each delivery process to finish before starting the next one. A delivery
3997 process may not actually do any deliveries if the retry times for the addresses
3998 have not been reached. Use &%-qf%& (see below) if you want to override this.
4001 .cindex "SMTP" "passed connection"
4002 .cindex "SMTP" "multiple deliveries"
4003 .cindex "multiple SMTP deliveries"
4004 the delivery process spawns other processes to deliver other messages down
4005 passed SMTP connections, the queue runner waits for these to finish before
4008 When all the queued messages have been considered, the original queue runner
4009 process terminates. In other words, a single pass is made over the waiting
4010 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4011 this to be repeated periodically.
4013 Exim processes the waiting messages in an unpredictable order. It isn't very
4014 random, but it is likely to be different each time, which is all that matters.
4015 If one particular message screws up a remote MTA, other messages to the same
4016 MTA have a chance of getting through if they get tried first.
4018 It is possible to cause the messages to be processed in lexical message id
4019 order, which is essentially the order in which they arrived, by setting the
4020 &%queue_run_in_order%& option, but this is not recommended for normal use.
4022 .vitem &%-q%&<&'qflags'&>
4023 The &%-q%& option may be followed by one or more flag letters that change its
4024 behaviour. They are all optional, but if more than one is present, they must
4025 appear in the correct order. Each flag is described in a separate item below.
4029 .cindex "queue" "double scanning"
4030 .cindex "queue" "routing"
4031 .cindex "routing" "whole queue before delivery"
4032 An option starting with &%-qq%& requests a two-stage queue run. In the first
4033 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4034 every domain. Addresses are routed, local deliveries happen, but no remote
4037 .cindex "hints database" "remembering routing"
4038 The hints database that remembers which messages are waiting for specific hosts
4039 is updated, as if delivery to those hosts had been deferred. After this is
4040 complete, a second, normal queue scan happens, with routing and delivery taking
4041 place as normal. Messages that are routed to the same host should mostly be
4042 delivered down a single SMTP
4043 .cindex "SMTP" "passed connection"
4044 .cindex "SMTP" "multiple deliveries"
4045 .cindex "multiple SMTP deliveries"
4046 connection because of the hints that were set up during the first queue scan.
4047 This option may be useful for hosts that are connected to the Internet
4050 .vitem &%-q[q]i...%&
4052 .cindex "queue" "initial delivery"
4053 If the &'i'& flag is present, the queue runner runs delivery processes only for
4054 those messages that haven't previously been tried. (&'i'& stands for &"initial
4055 delivery"&.) This can be helpful if you are putting messages on the queue using
4056 &%-odq%& and want a queue runner just to process the new messages.
4058 .vitem &%-q[q][i]f...%&
4060 .cindex "queue" "forcing delivery"
4061 .cindex "delivery" "forcing in queue run"
4062 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4063 message, whereas without &'f'& only those non-frozen addresses that have passed
4064 their retry times are tried.
4066 .vitem &%-q[q][i]ff...%&
4068 .cindex "frozen messages" "forcing delivery"
4069 If &'ff'& is present, a delivery attempt is forced for every message, whether
4072 .vitem &%-q[q][i][f[f]]l%&
4074 .cindex "queue" "local deliveries only"
4075 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4076 be done. If a message requires any remote deliveries, it remains on the queue
4079 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4080 .cindex "queue" "delivering specific messages"
4081 When scanning the queue, Exim can be made to skip over messages whose ids are
4082 lexically less than a given value by following the &%-q%& option with a
4083 starting message id. For example:
4085 exim -q 0t5C6f-0000c8-00
4087 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4088 second message id is given, messages whose ids are lexically greater than it
4089 are also skipped. If the same id is given twice, for example,
4091 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4093 just one delivery process is started, for that message. This differs from
4094 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4095 that it counts as a delivery from a queue run. Note that the selection
4096 mechanism does not affect the order in which the messages are scanned. There
4097 are also other ways of selecting specific sets of messages for delivery in a
4098 queue run &-- see &%-R%& and &%-S%&.
4100 .vitem &%-q%&<&'qflags'&><&'time'&>
4101 .cindex "queue runner" "starting periodically"
4102 .cindex "periodic queue running"
4103 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4104 starting a queue runner process at intervals specified by the given time value
4105 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4106 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4107 single daemon process handles both functions. A common way of starting up a
4108 combined daemon at system boot time is to use a command such as
4110 /usr/exim/bin/exim -bd -q30m
4112 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4113 process every 30 minutes.
4115 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4116 pid file is written unless one is explicitly requested by the &%-oP%& option.
4118 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4120 This option is synonymous with &%-R%&. It is provided for Sendmail
4123 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4125 This option is synonymous with &%-S%&.
4127 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4129 .cindex "queue runner" "for specific recipients"
4130 .cindex "delivery" "to given domain"
4131 .cindex "domain" "delivery to"
4132 The <&'rsflags'&> may be empty, in which case the white space before the string
4133 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4134 which are the possible values for <&'rsflags'&>. White space is required if
4135 <&'rsflags'&> is not empty.
4137 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4138 perform a single queue run, except that, when scanning the messages on the
4139 queue, Exim processes only those that have at least one undelivered recipient
4140 address containing the given string, which is checked in a case-independent
4141 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4142 regular expression; otherwise it is a literal string.
4144 Once a message is selected, all its addresses are processed. For the first
4145 selected message, Exim overrides any retry information and forces a delivery
4146 attempt for each undelivered address. This means that if delivery of any
4147 address in the first message is successful, any existing retry information is
4148 deleted, and so delivery attempts for that address in subsequently selected
4149 messages (which are processed without forcing) will run. However, if delivery
4150 of any address does not succeed, the retry information is updated, and in
4151 subsequently selected messages, the failing address will be skipped.
4153 .cindex "frozen messages" "forcing delivery"
4154 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4155 all selected messages, not just the first; frozen messages are included when
4158 The &%-R%& option makes it straightforward to initiate delivery of all messages
4159 to a given domain after a host has been down for some time. When the SMTP
4160 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4161 effect is to run Exim with the &%-R%& option, but it can be configured to run
4162 an arbitrary command instead.
4166 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4168 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4170 .cindex "delivery" "from given sender"
4171 .cindex "queue runner" "for specific senders"
4172 This option acts like &%-R%& except that it checks the string against each
4173 message's sender instead of against the recipients. If &%-R%& is also set, both
4174 conditions must be met for a message to be selected. If either of the options
4175 has &'f'& or &'ff'& in its flags, the associated action is taken.
4177 .vitem &%-Tqt%&&~<&'times'&>
4179 This an option that is exclusively for use by the Exim testing suite. It is not
4180 recognized when Exim is run normally. It allows for the setting up of explicit
4181 &"queue times"& so that various warning/retry features can be tested.
4185 .cindex "recipient" "extracting from header lines"
4186 .cindex "&'Bcc:'& header line"
4187 .cindex "&'Cc:'& header line"
4188 .cindex "&'To:'& header line"
4189 When Exim is receiving a locally-generated, non-SMTP message on its standard
4190 input, the &%-t%& option causes the recipients of the message to be obtained
4191 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4192 from the command arguments. The addresses are extracted before any rewriting
4193 takes place and the &'Bcc:'& header line, if present, is then removed.
4195 .cindex "Sendmail compatibility" "&%-t%& option"
4196 If the command has any arguments, they specify addresses to which the message
4197 is &'not'& to be delivered. That is, the argument addresses are removed from
4198 the recipients list obtained from the headers. This is compatible with Smail 3
4199 and in accordance with the documented behaviour of several versions of
4200 Sendmail, as described in man pages on a number of operating systems (e.g.
4201 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4202 argument addresses to those obtained from the headers, and the O'Reilly
4203 Sendmail book documents it that way. Exim can be made to add argument addresses
4204 instead of subtracting them by setting the option
4205 &%extract_addresses_remove_arguments%& false.
4207 .cindex "&%Resent-%& header lines" "with &%-t%&"
4208 If there are any &%Resent-%& header lines in the message, Exim extracts
4209 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4210 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4211 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4212 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4214 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4215 message is resent several times). The RFC also specifies that they should be
4216 added at the front of the message, and separated by &'Received:'& lines. It is
4217 not at all clear how &%-t%& should operate in the present of multiple sets,
4218 nor indeed exactly what constitutes a &"set"&.
4219 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4220 are often added at the end of the header, and if a message is resent more than
4221 once, it is common for the original set of &%Resent-%& headers to be renamed as
4222 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4226 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4227 compatibility with Sendmail.
4229 .vitem &%-tls-on-connect%&
4230 .oindex "&%-tls-on-connect%&"
4231 .cindex "TLS" "use without STARTTLS"
4232 .cindex "TLS" "automatic start"
4233 This option is available when Exim is compiled with TLS support. It forces all
4234 incoming SMTP connections to behave as if the incoming port is listed in the
4235 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4236 &<<CHAPTLS>>& for further details.
4241 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4242 Sendmail uses this option for &"initial message submission"&, and its
4243 documentation states that in future releases, it may complain about
4244 syntactically invalid messages rather than fixing them when this flag is not
4245 set. Exim ignores this option.
4249 This option causes Exim to write information to the standard error stream,
4250 describing what it is doing. In particular, it shows the log lines for
4251 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4252 dialogue is shown. Some of the log lines shown may not actually be written to
4253 the log if the setting of &%log_selector%& discards them. Any relevant
4254 selectors are shown with each log line. If none are shown, the logging is
4259 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4260 National Language Support extended characters in the body of the mail item"&).
4261 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4269 . ////////////////////////////////////////////////////////////////////////////
4270 . Insert a stylized DocBook comment here, to identify the end of the command
4271 . line options. This is for the benefit of the Perl script that automatically
4272 . creates a man page for the options.
4273 . ////////////////////////////////////////////////////////////////////////////
4276 <!-- === End of command line options === -->
4283 . ////////////////////////////////////////////////////////////////////////////
4284 . ////////////////////////////////////////////////////////////////////////////
4287 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4288 "The runtime configuration file"
4290 .cindex "run time configuration"
4291 .cindex "configuration file" "general description"
4292 .cindex "CONFIGURE_FILE"
4293 .cindex "configuration file" "errors in"
4294 .cindex "error" "in configuration file"
4295 .cindex "return code" "for bad configuration"
4296 Exim uses a single run time configuration file that is read whenever an Exim
4297 binary is executed. Note that in normal operation, this happens frequently,
4298 because Exim is designed to operate in a distributed manner, without central
4301 If a syntax error is detected while reading the configuration file, Exim
4302 writes a message on the standard error, and exits with a non-zero return code.
4303 The message is also written to the panic log. &*Note*&: Only simple syntax
4304 errors can be detected at this time. The values of any expanded options are
4305 not checked until the expansion happens, even when the expansion does not
4306 actually alter the string.
4308 The name of the configuration file is compiled into the binary for security
4309 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4310 most configurations, this specifies a single file. However, it is permitted to
4311 give a colon-separated list of file names, in which case Exim uses the first
4312 existing file in the list.
4315 .cindex "EXIM_GROUP"
4316 .cindex "CONFIGURE_OWNER"
4317 .cindex "CONFIGURE_GROUP"
4318 .cindex "configuration file" "ownership"
4319 .cindex "ownership" "configuration file"
4320 The run time configuration file must be owned by root or by the user that is
4321 specified at compile time by the EXIM_USER option, or by the user that is
4322 specified at compile time by the CONFIGURE_OWNER option (if set). The
4323 configuration file must not be world-writeable or group-writeable, unless its
4324 group is the one specified at compile time by the EXIM_GROUP option or by the
4325 CONFIGURE_GROUP option.
4327 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4328 to root, anybody who is able to edit the run time configuration file has an
4329 easy way to run commands as root. If you make your mail administrators members
4330 of the Exim group, but do not trust them with root, make sure that the run time
4331 configuration is not group writeable.
4333 A default configuration file, which will work correctly in simple situations,
4334 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4335 defines just one file name, the installation process copies the default
4336 configuration to a new file of that name if it did not previously exist. If
4337 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4338 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4343 .section "Using a different configuration file"
4344 .cindex "configuration file" "alternate"
4345 A one-off alternate configuration can be specified by the &%-C%& command line
4346 option, which may specify a single file or a list of files. However, when
4347 &%-C%& is used, Exim gives up its root privilege, unless called by root or the
4348 Exim user (or unless the argument for &%-C%& is identical to the built-in value
4349 from CONFIGURE_FILE). &%-C%& is useful mainly for checking the syntax of
4350 configuration files before installing them. No owner or group checks are done
4351 on a configuration file specified by &%-C%&.
4353 The privileged use of &%-C%& by the Exim user can be locked out by setting
4354 ALT_CONFIG_ROOT_ONLY in &_Local/Makefile_& when building Exim. However,
4355 if you do this, you also lock out the possibility of testing a
4356 configuration using &%-C%& right through message reception and delivery, even
4357 if the caller is root. The reception works, but by that time, Exim is running
4358 as the Exim user, so when it re-execs to regain privilege for the delivery, the
4359 use of &%-C%& causes privilege to be lost. However, root can test reception and
4360 delivery using two separate commands (one to put a message on the queue, using
4361 &%-odq%&, and another to do the delivery, using &%-M%&).
4363 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4364 prefix string with which any file named in a &%-C%& command line option must
4365 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4366 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4367 name can be used with &%-C%&.
4369 One-off changes to a configuration can be specified by the &%-D%& command line
4370 option, which defines and overrides values for macros used inside the
4371 configuration file. However, like &%-C%&, the use of this option by a
4372 non-privileged user causes Exim to discard its root privilege.
4373 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4374 completely disabled, and its use causes an immediate error exit.
4376 Some sites may wish to use the same Exim binary on different machines that
4377 share a file system, but to use different configuration files on each machine.
4378 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4379 looks for a file whose name is the configuration file name followed by a dot
4380 and the machine's node name, as obtained from the &[uname()]& function. If this
4381 file does not exist, the standard name is tried. This processing occurs for
4382 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4384 In some esoteric situations different versions of Exim may be run under
4385 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4386 help with this. See the comments in &_src/EDITME_& for details.
4390 .section "Configuration file format" "SECTconffilfor"
4391 .cindex "configuration file" "format of"
4392 .cindex "format" "configuration file"
4393 Exim's configuration file is divided into a number of different parts. General
4394 option settings must always appear at the start of the file. The other parts
4395 are all optional, and may appear in any order. Each part other than the first
4396 is introduced by the word &"begin"& followed by the name of the part. The
4400 &'ACL'&: Access control lists for controlling incoming SMTP mail.
4402 .cindex "AUTH" "configuration"
4403 &'authenticators'&: Configuration settings for the authenticator drivers. These
4404 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4406 &'routers'&: Configuration settings for the router drivers. Routers process
4407 addresses and determine how the message is to be delivered.
4409 &'transports'&: Configuration settings for the transport drivers. Transports
4410 define mechanisms for copying messages to destinations.
4412 &'retry'&: Retry rules, for use when a message cannot be immediately delivered.
4414 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4415 when new addresses are generated during delivery.
4417 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4418 want to use this feature, you must set
4420 LOCAL_SCAN_HAS_OPTIONS=yes
4422 in &_Local/Makefile_& before building Exim. Full details of the
4423 &[local_scan()]& facility are given in chapter &<<CHAPlocalscan>>&.
4426 .cindex "configuration file" "leading white space in"
4427 .cindex "configuration file" "trailing white space in"
4428 .cindex "white space" "in configuration file"
4429 Leading and trailing white space in configuration lines is always ignored.
4431 Blank lines in the file, and lines starting with a # character (ignoring
4432 leading white space) are treated as comments and are ignored. &*Note*&: A
4433 # character other than at the beginning of a line is not treated specially,
4434 and does not introduce a comment.
4436 Any non-comment line can be continued by ending it with a backslash. Note that
4437 the general rule for white space means that trailing white space after the
4438 backslash and leading white space at the start of continuation
4439 lines is ignored. Comment lines beginning with # (but not empty lines) may
4440 appear in the middle of a sequence of continuation lines.
4442 A convenient way to create a configuration file is to start from the
4443 default, which is supplied in &_src/configure.default_&, and add, delete, or
4444 change settings as required.
4446 The ACLs, retry rules, and rewriting rules have their own syntax which is
4447 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4448 respectively. The other parts of the configuration file have some syntactic
4449 items in common, and these are described below, from section &<<SECTcos>>&
4450 onwards. Before that, the inclusion, macro, and conditional facilities are
4455 .section "File inclusions in the configuration file"
4456 .cindex "inclusions in configuration file"
4457 .cindex "configuration file" "including other files"
4458 .cindex ".include in configuration file"
4459 .cindex ".include_if_exists in configuration file"
4460 You can include other files inside Exim's run time configuration file by
4463 &`.include`& <&'file name'&>
4464 &`.include_if_exists`& <&'file name'&>
4467 on a line by itself. Double quotes round the file name are optional. If you use
4468 the first form, a configuration error occurs if the file does not exist; the
4469 second form does nothing for non-existent files. In all cases, an absolute file
4473 Includes may be nested to any depth, but remember that Exim reads its
4474 configuration file often, so it is a good idea to keep them to a minimum.
4475 If you change the contents of an included file, you must HUP the daemon,
4476 because an included file is read only when the configuration itself is read.
4478 The processing of inclusions happens early, at a physical line level, so, like
4479 comment lines, an inclusion can be used in the middle of an option setting,
4482 hosts_lookup = a.b.c \
4485 Include processing happens after macro processing (see below). Its effect is to
4486 process the lines of the included file as if they occurred inline where the
4491 .section "Macros in the configuration file" "SECTmacrodefs"
4492 .cindex "macro" "description of"
4493 .cindex "configuration file" "macros"
4494 If a line in the main part of the configuration (that is, before the first
4495 &"begin"& line) begins with an upper case letter, it is taken as a macro
4496 definition, and must be of the form
4498 <&'name'&> = <&'rest of line'&>
4500 The name must consist of letters, digits, and underscores, and need not all be
4501 in upper case, though that is recommended. The rest of the line, including any
4502 continuations, is the replacement text, and has leading and trailing white
4503 space removed. Quotes are not removed. The replacement text can never end with
4504 a backslash character, but this doesn't seem to be a serious limitation.
4506 Macros may also be defined between router, transport, authenticator, or ACL
4507 definitions. They may not, however, be defined within an individual driver or
4508 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4510 .section "Macro substitution"
4511 Once a macro is defined, all subsequent lines in the file (and any included
4512 files) are scanned for the macro name; if there are several macros, the line is
4513 scanned for each in turn, in the order in which the macros are defined. The
4514 replacement text is not re-scanned for the current macro, though it is scanned
4515 for subsequently defined macros. For this reason, a macro name may not contain
4516 the name of a previously defined macro as a substring. You could, for example,
4519 &`ABCD_XYZ = `&<&'something'&>
4520 &`ABCD = `&<&'something else'&>
4522 but putting the definitions in the opposite order would provoke a configuration
4523 error. Macro expansion is applied to individual physical lines from the file,
4524 before checking for line continuation or file inclusion (see above). If a line
4525 consists solely of a macro name, and the expansion of the macro is empty, the
4526 line is ignored. A macro at the start of a line may turn the line into a
4527 comment line or a &`.include`& line.
4530 .section "Redefining macros"
4531 Once defined, the value of a macro can be redefined later in the configuration
4532 (or in an included file). Redefinition is specified by using &'=='& instead of
4537 MAC == updated value
4539 Redefinition does not alter the order in which the macros are applied to the
4540 subsequent lines of the configuration file. It is still the same order in which
4541 the macros were originally defined. All that changes is the macro's value.
4542 Redefinition makes it possible to accumulate values. For example:
4546 MAC == MAC and something added
4548 This can be helpful in situations where the configuration file is built
4549 from a number of other files.
4551 .section "Overriding macro values"
4552 The values set for macros in the configuration file can be overridden by the
4553 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4554 used, unless called by root or the Exim user. A definition on the command line
4555 using the &%-D%& option causes all definitions and redefinitions within the
4560 .section "Example of macro usage"
4561 As an example of macro usage, consider a configuration where aliases are looked
4562 up in a MySQL database. It helps to keep the file less cluttered if long
4563 strings such as SQL statements are defined separately as macros, for example:
4565 ALIAS_QUERY = select mailbox from user where \
4566 login=${quote_mysql:$local_part};
4568 This can then be used in a &(redirect)& router setting like this:
4570 data = ${lookup mysql{ALIAS_QUERY}}
4572 In earlier versions of Exim macros were sometimes used for domain, host, or
4573 address lists. In Exim 4 these are handled better by named lists &-- see
4574 section &<<SECTnamedlists>>&.
4577 .section "Conditional skips in the configuration file"
4578 .cindex "configuration file" "conditional skips"
4580 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4581 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4582 portions of the configuration file. The processing happens whenever the file is
4583 read (that is, when an Exim binary starts to run).
4585 The implementation is very simple. Instances of the first four directives must
4586 be followed by text that includes the names of one or macros. The condition
4587 that is tested is whether or not any macro substitution has taken place in the
4591 message_size_limit = 50M
4593 message_size_limit = 100M
4596 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
4597 otherwise. If there is more than one macro named on the line, the condition
4598 is true if any of them are defined. That is, it is an &"or"& condition. To
4599 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
4601 Although you can use a macro expansion to generate one of these directives,
4602 it is not very useful, because the condition &"there was a macro substitution
4603 in this line"& will always be true.
4605 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
4606 to clarify complicated nestings.
4610 .section "Common option syntax" "SECTcos"
4611 .cindex "common option syntax"
4612 .cindex "syntax of common options"
4613 .cindex "configuration file" "common option syntax"
4614 For the main set of options, driver options, and &[local_scan()]& options,
4615 each setting is on a line by itself, and starts with a name consisting of
4616 lower-case letters and underscores. Many options require a data value, and in
4617 these cases the name must be followed by an equals sign (with optional white
4618 space) and then the value. For example:
4620 qualify_domain = mydomain.example.com
4622 Some option settings may contain sensitive data, for example, passwords for
4623 accessing databases. To stop non-admin users from using the &%-bP%& command
4624 line option to read these values, you can precede the option settings with the
4625 word &"hide"&. For example:
4627 hide mysql_servers = localhost/users/admin/secret-password
4629 For non-admin users, such options are displayed like this:
4631 mysql_servers = <value not displayable>
4633 If &"hide"& is used on a driver option, it hides the value of that option on
4634 all instances of the same driver.
4636 The following sections describe the syntax used for the different data types
4637 that are found in option settings.
4640 .section "Boolean options"
4641 .cindex "format" "boolean"
4642 .cindex "boolean configuration values"
4643 .oindex "&%no_%&&'xxx'&"
4644 .oindex "&%not_%&&'xxx'&"
4645 Options whose type is given as boolean are on/off switches. There are two
4646 different ways of specifying such options: with and without a data value. If
4647 the option name is specified on its own without data, the switch is turned on;
4648 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
4649 boolean options may be followed by an equals sign and one of the words
4650 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
4651 the following two settings have exactly the same effect:
4656 The following two lines also have the same (opposite) effect:
4661 You can use whichever syntax you prefer.
4666 .section "Integer values"
4667 .cindex "integer configuration values"
4668 .cindex "format" "integer"
4669 If an integer data item starts with the characters &"0x"&, the remainder of it
4670 is interpreted as a hexadecimal number. Otherwise, it is treated as octal if it
4671 starts with the digit 0, and decimal if not. If an integer value is followed by
4672 the letter K, it is multiplied by 1024; if it is followed by the letter M, it
4673 is multiplied by 1024x1024.
4675 When the values of integer option settings are output, values which are an
4676 exact multiple of 1024 or 1024x1024 are
4677 sometimes, but not always,
4678 printed using the letters K and M. The printing style is independent of the
4679 actual input format that was used.
4682 .section "Octal integer values"
4683 .cindex "integer format"
4684 .cindex "format" "octal integer"
4685 The value of an option specified as an octal integer is always interpreted in
4686 octal, whether or not it starts with the digit zero. Such options are always
4691 .section "Fixed point number values"
4692 .cindex "fixed point configuration values"
4693 .cindex "format" "fixed point"
4694 A fixed point number consists of a decimal integer, optionally followed by a
4695 decimal point and up to three further digits.
4699 .section "Time interval values" "SECTtimeformat"
4700 .cindex "time interval" "specifying in configuration"
4701 .cindex "format" "time interval"
4702 A time interval is specified as a sequence of numbers, each followed by one of
4703 the following letters, with no intervening white space:
4706 .row &~&%s%& seconds
4707 .row &~&%m%& minutes
4713 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
4714 intervals are output in the same format. Exim does not restrict the values; it
4715 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
4719 .section "String values" "SECTstrings"
4720 .cindex "string" "format of configuration values"
4721 .cindex "format" "string"
4722 If a string data item does not start with a double-quote character, it is taken
4723 as consisting of the remainder of the line plus any continuation lines,
4724 starting at the first character after any leading white space, with trailing
4725 white space removed, and with no interpretation of the characters in the
4726 string. Because Exim removes comment lines (those beginning with #) at an early
4727 stage, they can appear in the middle of a multi-line string. The following
4728 settings are therefore equivalent:
4730 trusted_users = uucp:mail
4732 trusted_users = uucp:\
4733 # This comment line is ignored
4736 .cindex "string" "quoted"
4737 .cindex "escape characters in quoted strings"
4738 If a string does start with a double-quote, it must end with a closing
4739 double-quote, and any backslash characters other than those used for line
4740 continuation are interpreted as escape characters, as follows:
4743 .row &~&`\\`& "single backslash"
4744 .row &~&`\n`& "newline"
4745 .row &~&`\r`& "carriage return"
4747 .row "&~&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
4748 .row "&~&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
4752 If a backslash is followed by some other character, including a double-quote
4753 character, that character replaces the pair.
4755 Quoting is necessary only if you want to make use of the backslash escapes to
4756 insert special characters, or if you need to specify a value with leading or
4757 trailing spaces. These cases are rare, so quoting is almost never needed in
4758 current versions of Exim. In versions of Exim before 3.14, quoting was required
4759 in order to continue lines, so you may come across older configuration files
4760 and examples that apparently quote unnecessarily.
4763 .section "Expanded strings"
4764 .cindex "string expansion" "definition of"
4765 .cindex "expansion" "definition of"
4766 Some strings in the configuration file are subjected to &'string expansion'&,
4767 by which means various parts of the string may be changed according to the
4768 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
4769 is as just described; in particular, the handling of backslashes in quoted
4770 strings is done as part of the input process, before expansion takes place.
4771 However, backslash is also an escape character for the expander, so any
4772 backslashes that are required for that reason must be doubled if they are
4773 within a quoted configuration string.
4776 .section "User and group names"
4777 .cindex "user name" "format of"
4778 .cindex "format" "user name"
4779 .cindex "group" "name format"
4780 .cindex "format" "group name"
4781 User and group names are specified as strings, using the syntax described
4782 above, but the strings are interpreted specially. A user or group name must
4783 either consist entirely of digits, or be a name that can be looked up using the
4784 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
4787 .section "List construction" "SECTlistconstruct"
4788 .cindex "list" "syntax of in configuration"
4789 .cindex "format" "list item in configuration"
4790 .cindex "string list" "definition"
4791 The data for some configuration options is a list of items, with colon as the
4792 default separator. Many of these options are shown with type &"string list"& in
4793 the descriptions later in this document. Others are listed as &"domain list"&,
4794 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
4795 are all the same; however, those other than &"string list"& are subject to
4796 particular kinds of interpretation, as described in chapter
4797 &<<CHAPdomhosaddlists>>&.
4799 In all these cases, the entire list is treated as a single string as far as the
4800 input syntax is concerned. The &%trusted_users%& setting in section
4801 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
4802 in a list, it must be entered as two colons. Leading and trailing white space
4803 on each item in a list is ignored. This makes it possible to include items that
4804 start with a colon, and in particular, certain forms of IPv6 address. For
4807 local_interfaces = 127.0.0.1 : ::::1
4809 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
4811 &*Note*&: Although leading and trailing white space is ignored in individual
4812 list items, it is not ignored when parsing the list. The space after the first
4813 colon in the example above is necessary. If it were not there, the list would
4814 be interpreted as the two items 127.0.0.1:: and 1.
4816 .cindex "list separator" "changing"
4817 .cindex "IPv6" "addresses in lists"
4818 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
4819 introduced to allow the separator character to be changed. If a list begins
4820 with a left angle bracket, followed by any punctuation character, that
4821 character is used instead of colon as the list separator. For example, the list
4822 above can be rewritten to use a semicolon separator like this:
4824 local_interfaces = <; 127.0.0.1 ; ::1
4826 This facility applies to all lists, with the exception of the list in
4827 &%log_file_path%&. It is recommended that the use of non-colon separators be
4828 confined to circumstances where they really are needed.
4832 .section "Empty items in lists" "SECTempitelis"
4833 .cindex "list" "empty item in"
4834 An empty item at the end of a list is always ignored. In other words, trailing
4835 separator characters are ignored. Thus, the list in
4837 senders = user@domain :
4839 contains only a single item. If you want to include an empty string as one item
4840 in a list, it must not be the last item. For example, this list contains three
4841 items, the second of which is empty:
4843 senders = user1@domain : : user2@domain
4845 &*Note*&: There must be white space between the two colons, as otherwise they
4846 are interpreted as representing a single colon data character (and the list
4847 would then contain just one item). If you want to specify a list that contains
4848 just one, empty item, you can do it as in this example:
4852 In this case, the first item is empty, and the second is discarded because it
4853 is at the end of the list.
4858 .section "Format of driver configurations" "SECTfordricon"
4859 .cindex "drivers" "configuration format"
4860 There are separate parts in the configuration for defining routers, transports,
4861 and authenticators. In each part, you are defining a number of driver
4862 instances, each with its own set of options. Each driver instance is defined by
4863 a sequence of lines like this:
4865 <&'instance name'&>:
4870 In the following example, the instance name is &(localuser)&, and it is
4871 followed by three options settings:
4876 transport = local_delivery
4878 For each driver instance, you specify which Exim code module it uses &-- by the
4879 setting of the &%driver%& option &-- and (optionally) some configuration
4880 settings. For example, in the case of transports, if you want a transport to
4881 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
4882 a local file you would use the &(appendfile)& driver. Each of the drivers is
4883 described in detail in its own separate chapter later in this manual.
4885 You can have several routers, transports, or authenticators that are based on
4886 the same underlying driver (each must have a different instance name).
4888 The order in which routers are defined is important, because addresses are
4889 passed to individual routers one by one, in order. The order in which
4890 transports are defined does not matter at all. The order in which
4891 authenticators are defined is used only when Exim, as a client, is searching
4892 them to find one that matches an authentication mechanism offered by the
4895 .cindex "generic options"
4896 .cindex "options" "generic &-- definition of"
4897 Within a driver instance definition, there are two kinds of option: &'generic'&
4898 and &'private'&. The generic options are those that apply to all drivers of the
4899 same type (that is, all routers, all transports or all authenticators). The
4900 &%driver%& option is a generic option that must appear in every definition.
4901 .cindex "private options"
4902 The private options are special for each driver, and none need appear, because
4903 they all have default values.
4905 The options may appear in any order, except that the &%driver%& option must
4906 precede any private options, since these depend on the particular driver. For
4907 this reason, it is recommended that &%driver%& always be the first option.
4909 Driver instance names, which are used for reference in log entries and
4910 elsewhere, can be any sequence of letters, digits, and underscores (starting
4911 with a letter) and must be unique among drivers of the same type. A router and
4912 a transport (for example) can each have the same name, but no two router
4913 instances can have the same name. The name of a driver instance should not be
4914 confused with the name of the underlying driver module. For example, the
4915 configuration lines:
4920 create an instance of the &(smtp)& transport driver whose name is
4921 &(remote_smtp)&. The same driver code can be used more than once, with
4922 different instance names and different option settings each time. A second
4923 instance of the &(smtp)& transport, with different options, might be defined
4929 command_timeout = 10s
4931 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
4932 these transport instances from routers, and these names would appear in log
4935 Comment lines may be present in the middle of driver specifications. The full
4936 list of option settings for any particular driver instance, including all the
4937 defaulted values, can be extracted by making use of the &%-bP%& command line
4945 . ////////////////////////////////////////////////////////////////////////////
4946 . ////////////////////////////////////////////////////////////////////////////
4948 .chapter "The default configuration file" "CHAPdefconfil"
4949 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
4950 .cindex "default" "configuration file &""walk through""&"
4951 The default configuration file supplied with Exim as &_src/configure.default_&
4952 is sufficient for a host with simple mail requirements. As an introduction to
4953 the way Exim is configured, this chapter &"walks through"& the default
4954 configuration, giving brief explanations of the settings. Detailed descriptions
4955 of the options are given in subsequent chapters. The default configuration file
4956 itself contains extensive comments about ways you might want to modify the
4957 initial settings. However, note that there are many options that are not
4958 mentioned at all in the default configuration.
4962 .section "Main configuration settings"
4963 The main (global) configuration option settings must always come first in the
4964 file. The first thing you'll see in the file, after some initial comments, is
4967 # primary_hostname =
4969 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
4970 to know the official, fully qualified name of your host, and this is where you
4971 can specify it. However, in most cases you do not need to set this option. When
4972 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
4974 The first three non-comment configuration lines are as follows:
4976 domainlist local_domains = @
4977 domainlist relay_to_domains =
4978 hostlist relay_from_hosts = 127.0.0.1
4980 These are not, in fact, option settings. They are definitions of two named
4981 domain lists and one named host list. Exim allows you to give names to lists of
4982 domains, hosts, and email addresses, in order to make it easier to manage the
4983 configuration file (see section &<<SECTnamedlists>>&).
4985 The first line defines a domain list called &'local_domains'&; this is used
4986 later in the configuration to identify domains that are to be delivered
4989 .cindex "@ in a domain list"
4990 There is just one item in this list, the string &"@"&. This is a special form
4991 of entry which means &"the name of the local host"&. Thus, if the local host is
4992 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
4993 be delivered locally. Because the local host's name is referenced indirectly,
4994 the same configuration file can be used on different hosts.
4996 The second line defines a domain list called &'relay_to_domains'&, but the
4997 list itself is empty. Later in the configuration we will come to the part that
4998 controls mail relaying through the local host; it allows relaying to any
4999 domains in this list. By default, therefore, no relaying on the basis of a mail
5000 domain is permitted.
5002 The third line defines a host list called &'relay_from_hosts'&. This list is
5003 used later in the configuration to permit relaying from any host or IP address
5004 that matches the list. The default contains just the IP address of the IPv4
5005 loopback interface, which means that processes on the local host are able to
5006 submit mail for relaying by sending it over TCP/IP to that interface. No other
5007 hosts are permitted to submit messages for relaying.
5009 Just to be sure there's no misunderstanding: at this point in the configuration
5010 we aren't actually setting up any controls. We are just defining some domains
5011 and hosts that will be used in the controls that are specified later.
5013 The next two configuration lines are genuine option settings:
5015 acl_smtp_rcpt = acl_check_rcpt
5016 acl_smtp_data = acl_check_data
5018 These options specify &'Access Control Lists'& (ACLs) that are to be used
5019 during an incoming SMTP session for every recipient of a message (every RCPT
5020 command), and after the contents of the message have been received,
5021 respectively. The names of the lists are &'acl_check_rcpt'& and
5022 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5023 section of the configuration. The RCPT ACL controls which recipients are
5024 accepted for an incoming message &-- if a configuration does not provide an ACL
5025 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5026 contents of a message to be checked.
5028 Two commented-out option settings are next:
5030 # av_scanner = clamd:/tmp/clamd
5031 # spamd_address = 127.0.0.1 783
5033 These are example settings that can be used when Exim is compiled with the
5034 content-scanning extension. The first specifies the interface to the virus
5035 scanner, and the second specifies the interface to SpamAssassin. Further
5036 details are given in chapter &<<CHAPexiscan>>&.
5038 Two more commented-out options settings follow:
5041 # qualify_recipient =
5043 The first of these specifies a domain that Exim uses when it constructs a
5044 complete email address from a local login name. This is often needed when Exim
5045 receives a message from a local process. If you do not set &%qualify_domain%&,
5046 the value of &%primary_hostname%& is used. If you set both of these options,
5047 you can have different qualification domains for sender and recipient
5048 addresses. If you set only the first one, its value is used in both cases.
5050 .cindex "domain literal" "recognizing format"
5051 The following line must be uncommented if you want Exim to recognize
5052 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5053 (an IP address within square brackets) instead of a named domain.
5055 # allow_domain_literals
5057 The RFCs still require this form, but many people think that in the modern
5058 Internet it makes little sense to permit mail to be sent to specific hosts by
5059 quoting their IP addresses. This ancient format has been used by people who
5060 try to abuse hosts by using them for unwanted relaying. However, some
5061 people believe there are circumstances (for example, messages addressed to
5062 &'postmaster'&) where domain literals are still useful.
5064 The next configuration line is a kind of trigger guard:
5068 It specifies that no delivery must ever be run as the root user. The normal
5069 convention is to set up &'root'& as an alias for the system administrator. This
5070 setting is a guard against slips in the configuration.
5071 The list of users specified by &%never_users%& is not, however, the complete
5072 list; the build-time configuration in &_Local/Makefile_& has an option called
5073 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5074 contents of &%never_users%& are added to this list. By default
5075 FIXED_NEVER_USERS also specifies root.
5077 When a remote host connects to Exim in order to send mail, the only information
5078 Exim has about the host's identity is its IP address. The next configuration
5083 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5084 in order to get a host name. This improves the quality of the logging
5085 information, but if you feel it is too expensive, you can remove it entirely,
5086 or restrict the lookup to hosts on &"nearby"& networks.
5087 Note that it is not always possible to find a host name from an IP address,
5088 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5091 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5092 1413 (hence their names):
5095 rfc1413_query_timeout = 30s
5097 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5098 You can limit the hosts to which these calls are made, or change the timeout
5099 that is used. If you set the timeout to zero, all ident calls are disabled.
5100 Although they are cheap and can provide useful information for tracing problem
5101 messages, some hosts and firewalls have problems with ident calls. This can
5102 result in a timeout instead of an immediate refused connection, leading to
5103 delays on starting up an incoming SMTP session.
5105 When Exim receives messages over SMTP connections, it expects all addresses to
5106 be fully qualified with a domain, as required by the SMTP definition. However,
5107 if you are running a server to which simple clients submit messages, you may
5108 find that they send unqualified addresses. The two commented-out options:
5110 # sender_unqualified_hosts =
5111 # recipient_unqualified_hosts =
5113 show how you can specify hosts that are permitted to send unqualified sender
5114 and recipient addresses, respectively.
5116 The &%percent_hack_domains%& option is also commented out:
5118 # percent_hack_domains =
5120 It provides a list of domains for which the &"percent hack"& is to operate.
5121 This is an almost obsolete form of explicit email routing. If you do not know
5122 anything about it, you can safely ignore this topic.
5124 The last two settings in the main part of the default configuration are
5125 concerned with messages that have been &"frozen"& on Exim's queue. When a
5126 message is frozen, Exim no longer continues to try to deliver it. Freezing
5127 occurs when a bounce message encounters a permanent failure because the sender
5128 address of the original message that caused the bounce is invalid, so the
5129 bounce cannot be delivered. This is probably the most common case, but there
5130 are also other conditions that cause freezing, and frozen messages are not
5131 always bounce messages.
5133 ignore_bounce_errors_after = 2d
5134 timeout_frozen_after = 7d
5136 The first of these options specifies that failing bounce messages are to be
5137 discarded after 2 days on the queue. The second specifies that any frozen
5138 message (whether a bounce message or not) is to be timed out (and discarded)
5139 after a week. In this configuration, the first setting ensures that no failing
5140 bounce message ever lasts a week.
5144 .section "ACL configuration"
5145 .cindex "default" "ACLs"
5146 .cindex "&ACL;" "default configuration"
5147 In the default configuration, the ACL section follows the main configuration.
5148 It starts with the line
5152 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5153 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5154 and &%acl_smtp_data%& above.
5156 .cindex "RCPT" "ACL for"
5157 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5158 RCPT command specifies one of the message's recipients. The ACL statements
5159 are considered in order, until the recipient address is either accepted or
5160 rejected. The RCPT command is then accepted or rejected, according to the
5161 result of the ACL processing.
5165 This line, consisting of a name terminated by a colon, marks the start of the
5170 This ACL statement accepts the recipient if the sending host matches the list.
5171 But what does that strange list mean? It doesn't actually contain any host
5172 names or IP addresses. The presence of the colon puts an empty item in the
5173 list; Exim matches this only if the incoming message did not come from a remote
5174 host, because in that case, the remote hostname is empty. The colon is
5175 important. Without it, the list itself is empty, and can never match anything.
5177 What this statement is doing is to accept unconditionally all recipients in
5178 messages that are submitted by SMTP from local processes using the standard
5179 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5182 deny message = Restricted characters in address
5183 domains = +local_domains
5184 local_parts = ^[.] : ^.*[@%!/|]
5186 deny message = Restricted characters in address
5187 domains = !+local_domains
5188 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5190 These statements are concerned with local parts that contain any of the
5191 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5192 Although these characters are entirely legal in local parts (in the case of
5193 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5194 in Internet mail addresses.
5196 The first three have in the past been associated with explicitly routed
5197 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5198 option). Addresses containing these characters are regularly tried by spammers
5199 in an attempt to bypass relaying restrictions, and also by open relay testing
5200 programs. Unless you really need them it is safest to reject these characters
5201 at this early stage. This configuration is heavy-handed in rejecting these
5202 characters for all messages it accepts from remote hosts. This is a deliberate
5203 policy of being as safe as possible.
5205 The first rule above is stricter, and is applied to messages that are addressed
5206 to one of the local domains handled by this host. This is implemented by the
5207 first condition, which restricts it to domains that are listed in the
5208 &'local_domains'& domain list. The &"+"& character is used to indicate a
5209 reference to a named list. In this configuration, there is just one domain in
5210 &'local_domains'&, but in general there may be many.
5212 The second condition on the first statement uses two regular expressions to
5213 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5214 or &"|"&. If you have local accounts that include these characters, you will
5215 have to modify this rule.
5217 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5218 allows them because they have been encountered in practice. (Consider the
5219 common convention of local parts constructed as
5220 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5221 the author of Exim, who has no second initial.) However, a local part starting
5222 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5223 file name (for example, for a mailing list). This is also true for local parts
5224 that contain slashes. A pipe symbol can also be troublesome if the local part
5225 is incorporated unthinkingly into a shell command line.
5227 The second rule above applies to all other domains, and is less strict. This
5228 allows your own users to send outgoing messages to sites that use slashes
5229 and vertical bars in their local parts. It blocks local parts that begin
5230 with a dot, slash, or vertical bar, but allows these characters within the
5231 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5232 and &"!"& is blocked, as before. The motivation here is to prevent your users
5233 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5235 accept local_parts = postmaster
5236 domains = +local_domains
5238 This statement, which has two conditions, accepts an incoming address if the
5239 local part is &'postmaster'& and the domain is one of those listed in the
5240 &'local_domains'& domain list. The &"+"& character is used to indicate a
5241 reference to a named list. In this configuration, there is just one domain in
5242 &'local_domains'&, but in general there may be many.
5244 The presence of this statement means that mail to postmaster is never blocked
5245 by any of the subsequent tests. This can be helpful while sorting out problems
5246 in cases where the subsequent tests are incorrectly denying access.
5248 require verify = sender
5250 This statement requires the sender address to be verified before any subsequent
5251 ACL statement can be used. If verification fails, the incoming recipient
5252 address is refused. Verification consists of trying to route the address, to
5253 see if a bounce message could be delivered to it. In the case of remote
5254 addresses, basic verification checks only the domain, but &'callouts'& can be
5255 used for more verification if required. Section &<<SECTaddressverification>>&
5256 discusses the details of address verification.
5258 accept hosts = +relay_from_hosts
5259 control = submission
5261 This statement accepts the address if the message is coming from one of the
5262 hosts that are defined as being allowed to relay through this host. Recipient
5263 verification is omitted here, because in many cases the clients are dumb MUAs
5264 that do not cope well with SMTP error responses. For the same reason, the
5265 second line specifies &"submission mode"& for messages that are accepted. This
5266 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5267 messages that are deficient in some way, for example, because they lack a
5268 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5269 probably add recipient verification here, and disable submission mode.
5271 accept authenticated = *
5272 control = submission
5274 This statement accepts the address if the client host has authenticated itself.
5275 Submission mode is again specified, on the grounds that such messages are most
5276 likely to come from MUAs. The default configuration does not define any
5277 authenticators, which means that no client can in fact authenticate. You will
5278 need to add authenticator definitions if you want to make use of this ACL
5281 # deny message = rejected because $sender_host_address \
5282 # is in a black list at $dnslist_domain\n\
5284 # dnslists = black.list.example
5286 # warn message = X-Warning: $sender_host_address is \
5287 # in a black list at $dnslist_domain
5288 # log_message = found in $dnslist_domain
5289 # dnslists = black.list.example
5291 These commented-out lines are examples of how you could configure Exim to check
5292 sending hosts against a DNS black list. The first statement rejects messages
5293 from blacklisted hosts, whereas the second merely inserts a warning header
5296 accept domains = +local_domains
5300 This statement accepts the incoming recipient address if its domain is one of
5301 the local domains, but only if the address can be verified. Verification of
5302 local addresses normally checks both the local part and the domain. The
5303 &%endpass%& line needs some explanation: if the condition above &%endpass%&
5304 fails, that is, if the address is not in a local domain, control is passed to
5305 the next ACL statement. However, if the condition below &%endpass%& fails, that
5306 is, if a recipient in a local domain cannot be verified, access is denied and
5307 the recipient is rejected.
5309 accept domains = +relay_to_domains
5313 This statement accepts the incoming recipient address if its domain is one of
5314 the domains for which this host is a relay, but again, only if the address can
5317 deny message = relay not permitted
5319 The final statement denies access, giving a specific error message. Reaching
5320 the end of the ACL also causes access to be denied, but with the generic
5321 message &"administrative prohibition"&.
5325 This line marks the start of the second ACL, and names it. Most of the contents
5326 of this ACL are commented out:
5329 # message = This message contains a virus \
5332 These lines are examples of how to arrange for messages to be scanned for
5333 viruses when Exim has been compiled with the content-scanning extension, and a
5334 suitable virus scanner is installed. If the message is found to contain a
5335 virus, it is rejected with the given custom error message.
5337 # warn spam = nobody
5338 # message = X-Spam_score: $spam_score\n\
5339 # X-Spam_score_int: $spam_score_int\n\
5340 # X-Spam_bar: $spam_bar\n\
5341 # X-Spam_report: $spam_report
5343 These lines are an example of how to arrange for messages to be scanned by
5344 SpamAssassin when Exim has been compiled with the content-scanning extension,
5345 and SpamAssassin has been installed. The SpamAssassin check is run with
5346 &`nobody`& as its user parameter, and the results are added to the message as a
5347 series of extra header line. In this case, the message is not rejected,
5348 whatever the spam score.
5352 This final line in the DATA ACL accepts the message unconditionally.
5355 .section "Router configuration"
5356 .cindex "default" "routers"
5357 .cindex "routers" "default"
5358 The router configuration comes next in the default configuration, introduced
5363 Routers are the modules in Exim that make decisions about where to send
5364 messages. An address is passed to each router in turn, until it is either
5365 accepted, or failed. This means that the order in which you define the routers
5366 matters. Each router is fully described in its own chapter later in this
5367 manual. Here we give only brief overviews.
5370 # driver = ipliteral
5371 # domains = !+local_domains
5372 # transport = remote_smtp
5374 .cindex "domain literal" "default router"
5375 This router is commented out because the majority of sites do not want to
5376 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5377 you uncomment this router, you also need to uncomment the setting of
5378 &%allow_domain_literals%& in the main part of the configuration.
5382 domains = ! +local_domains
5383 transport = remote_smtp
5384 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5387 The first uncommented router handles addresses that do not involve any local
5388 domains. This is specified by the line
5390 domains = ! +local_domains
5392 The &%domains%& option lists the domains to which this router applies, but the
5393 exclamation mark is a negation sign, so the router is used only for domains
5394 that are not in the domain list called &'local_domains'& (which was defined at
5395 the start of the configuration). The plus sign before &'local_domains'&
5396 indicates that it is referring to a named list. Addresses in other domains are
5397 passed on to the following routers.
5399 The name of the router driver is &(dnslookup)&,
5400 and is specified by the &%driver%& option. Do not be confused by the fact that
5401 the name of this router instance is the same as the name of the driver. The
5402 instance name is arbitrary, but the name set in the &%driver%& option must be
5403 one of the driver modules that is in the Exim binary.
5405 The &(dnslookup)& router routes addresses by looking up their domains in the
5406 DNS in order to obtain a list of hosts to which the address is routed. If the
5407 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5408 specified by the &%transport%& option. If the router does not find the domain
5409 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5410 the address fails and is bounced.
5412 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5413 be entirely ignored. This option is present because a number of cases have been
5414 encountered where MX records in the DNS point to host names
5415 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5416 Completely ignoring these IP addresses causes Exim to fail to route the
5417 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5418 continue to try to deliver the message periodically until the address timed
5425 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5427 file_transport = address_file
5428 pipe_transport = address_pipe
5430 Control reaches this and subsequent routers only for addresses in the local
5431 domains. This router checks to see whether the local part is defined as an
5432 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5433 data that it looks up from that file. If no data is found for the local part,
5434 the value of the &%data%& option is empty, causing the address to be passed to
5437 &_/etc/aliases_& is a conventional name for the system aliases file that is
5438 often used. That is why it is referenced by from the default configuration
5439 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5440 &_Local/Makefile_& before building Exim.
5445 # local_part_suffix = +* : -*
5446 # local_part_suffix_optional
5447 file = $home/.forward
5452 file_transport = address_file
5453 pipe_transport = address_pipe
5454 reply_transport = address_reply
5456 This is the most complicated router in the default configuration. It is another
5457 redirection router, but this time it is looking for forwarding data set up by
5458 individual users. The &%check_local_user%& setting specifies a check that the
5459 local part of the address is the login name of a local user. If it is not, the
5460 router is skipped. The two commented options that follow &%check_local_user%&,
5463 # local_part_suffix = +* : -*
5464 # local_part_suffix_optional
5466 .cindex "&$local_part_suffix$&"
5467 show how you can specify the recognition of local part suffixes. If the first
5468 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5469 by any sequence of characters, is removed from the local part and placed in the
5470 variable &$local_part_suffix$&. The second suffix option specifies that the
5471 presence of a suffix in the local part is optional. When a suffix is present,
5472 the check for a local login uses the local part with the suffix removed.
5474 When a local user account is found, the file called &_.forward_& in the user's
5475 home directory is consulted. If it does not exist, or is empty, the router
5476 declines. Otherwise, the contents of &_.forward_& are interpreted as
5477 redirection data (see chapter &<<CHAPredirect>>& for more details).
5479 .cindex "Sieve filter" "enabling in default router"
5480 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5481 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5482 is commented out by default), the contents of the file are interpreted as a set
5483 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5484 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5485 separate document entitled &'Exim's interfaces to mail filtering'&.
5487 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5488 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5489 There are two reasons for doing this:
5492 Whether or not a local user has a &_.forward_& file is not really relevant when
5493 checking an address for validity; it makes sense not to waste resources doing
5496 More importantly, when Exim is verifying addresses or handling an EXPN
5497 command during an SMTP session, it is running as the Exim user, not as root.
5498 The group is the Exim group, and no additional groups are set up.
5499 It may therefore not be possible for Exim to read users' &_.forward_& files at
5503 The setting of &%check_ancestor%& prevents the router from generating a new
5504 address that is the same as any previous address that was redirected. (This
5505 works round a problem concerning a bad interaction between aliasing and
5506 forwarding &-- see section &<<SECTredlocmai>>&).
5508 The final three option settings specify the transports that are to be used when
5509 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5510 auto-reply, respectively. For example, if a &_.forward_& file contains
5512 a.nother@elsewhere.example, /home/spqr/archive
5514 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5520 # local_part_suffix = +* : -*
5521 # local_part_suffix_optional
5522 transport = local_delivery
5524 The final router sets up delivery into local mailboxes, provided that the local
5525 part is the name of a local login, by accepting the address and assigning it to
5526 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5527 routers, so the address is bounced. The commented suffix settings fulfil the
5528 same purpose as they do for the &(userforward)& router.
5531 .section "Transport configuration"
5532 .cindex "default" "transports"
5533 .cindex "transports" "default"
5534 Transports define mechanisms for actually delivering messages. They operate
5535 only when referenced from routers, so the order in which they are defined does
5536 not matter. The transports section of the configuration starts with
5540 One remote transport and four local transports are defined.
5545 This transport is used for delivering messages over SMTP connections. All its
5546 options are defaulted. The list of remote hosts comes from the router.
5550 file = /var/mail/$local_part
5557 This &(appendfile)& transport is used for local delivery to user mailboxes in
5558 traditional BSD mailbox format. By default it runs under the uid and gid of the
5559 local user, which requires the sticky bit to be set on the &_/var/mail_&
5560 directory. Some systems use the alternative approach of running mail deliveries
5561 under a particular group instead of using the sticky bit. The commented options
5562 show how this can be done.
5564 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
5565 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
5566 similarly-named options above.
5572 This transport is used for handling deliveries to pipes that are generated by
5573 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
5574 option specifies that any output generated by the pipe is to be returned to the
5583 This transport is used for handling deliveries to files that are generated by
5584 redirection. The name of the file is not specified in this instance of
5585 &(appendfile)&, because it comes from the &(redirect)& router.
5590 This transport is used for handling automatic replies generated by users'
5595 .section "Default retry rule"
5596 .cindex "retry" "default rule"
5597 .cindex "default" "retry rule"
5598 The retry section of the configuration file contains rules which affect the way
5599 Exim retries deliveries that cannot be completed at the first attempt. It is
5600 introduced by the line
5604 In the default configuration, there is just one rule, which applies to all
5607 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5609 This causes any temporarily failing address to be retried every 15 minutes for
5610 2 hours, then at intervals starting at one hour and increasing by a factor of
5611 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5612 is not delivered after 4 days of temporary failure, it is bounced.
5616 .section "Rewriting configuration"
5617 The rewriting section of the configuration, introduced by
5621 contains rules for rewriting addresses in messages as they arrive. There are no
5622 rewriting rules in the default configuration file.
5626 .section "Authenticators configuration"
5627 .cindex "AUTH" "configuration"
5628 The authenticators section of the configuration, introduced by
5630 begin authenticators
5632 defines mechanisms for the use of the SMTP AUTH command. No authenticators
5633 are specified in the default configuration file.
5634 .ecindex IIDconfiwal
5638 . ////////////////////////////////////////////////////////////////////////////
5639 . ////////////////////////////////////////////////////////////////////////////
5641 .chapter "Regular expressions" "CHAPregexp"
5643 .cindex "regular expressions" "library"
5645 Exim supports the use of regular expressions in many of its options. It
5646 uses the PCRE regular expression library; this provides regular expression
5647 matching that is compatible with Perl 5. The syntax and semantics of
5648 regular expressions is discussed in many Perl reference books, and also in
5649 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
5650 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
5652 The documentation for the syntax and semantics of the regular expressions that
5653 are supported by PCRE is included in plain text in the file
5654 &_doc/pcrepattern.txt_& in the Exim distribution, and also in the HTML
5655 tarbundle of Exim documentation. It describes in detail the features of the
5656 regular expressions that PCRE supports, so no further description is included
5657 here. The PCRE functions are called from Exim using the default option settings
5658 (that is, with no PCRE options set), except that the PCRE_CASELESS option is
5659 set when the matching is required to be case-insensitive.
5661 In most cases, when a regular expression is required in an Exim configuration,
5662 it has to start with a circumflex, in order to distinguish it from plain text
5663 or an &"ends with"& wildcard. In this example of a configuration setting, the
5664 second item in the colon-separated list is a regular expression.
5666 domains = a.b.c : ^\\d{3} : *.y.z : ...
5668 The doubling of the backslash is required because of string expansion that
5669 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
5670 of this issue, and a way of avoiding the need for doubling backslashes. The
5671 regular expression that is eventually used in this example contains just one
5672 backslash. The circumflex is included in the regular expression, and has the
5673 normal effect of &"anchoring"& it to the start of the string that is being
5676 There are, however, two cases where a circumflex is not required for the
5677 recognition of a regular expression: these are the &%match%& condition in a
5678 string expansion, and the &%matches%& condition in an Exim filter file. In
5679 these cases, the relevant string is always treated as a regular expression; if
5680 it does not start with a circumflex, the expression is not anchored, and can
5681 match anywhere in the subject string.
5683 In all cases, if you want a regular expression to match at the end of a string,
5684 you must code the $ metacharacter to indicate this. For example:
5686 domains = ^\\d{3}\\.example
5688 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
5691 domains = ^\\d{3}\\.example\$
5693 if you want &'example'& to be the top-level domain. The backslash before the
5694 $ is needed because string expansion also interprets dollar characters.
5698 .section "Testing regular expressions"
5699 .cindex "testing" "regular expressions"
5700 .cindex "regular expressions" "testing"
5701 .cindex "&'pcretest'&"
5702 A program called &'pcretest'& forms part of the PCRE distribution and is built
5703 with PCRE during the process of building Exim. It is primarily intended for
5704 testing PCRE itself, but it can also be used for experimenting with regular
5705 expressions. After building Exim, the binary can be found in the build
5706 directory (it is not installed anywhere automatically). There is documentation
5707 of various options in &_doc/pcretest.txt_&, but for simple testing, none are
5708 needed. This is the output of a sample run of &'pcretest'&:
5710 &` re> `&&*&`/^([@]+)@.+\.(ac|edu)\.(?!kr)[a-z]{2}$/`&*&
5711 &`data> `&&*&`x@y.ac.uk`&*&
5715 &`data> `&&*&`x@y.ac.kr`&*&
5717 &`data> `&&*&`x@y.edu.com`&*&
5719 &`data> `&&*&`x@y.edu.co`&*&
5724 Input typed by the user is shown in bold face. After the &"re>"& prompt, a
5725 regular expression enclosed in delimiters is expected. If this compiles without
5726 error, &"data>"& prompts are given for strings against which the expression is
5727 matched. An empty data line causes a new regular expression to be read. If the
5728 match is successful, the captured substring values (that is, what would be in
5729 the variables &$0$&, &$1$&, &$2$&, etc.) are shown. The above example tests for
5730 an email address whose domain ends with either &"ac"& or &"edu"& followed by a
5731 two-character top-level domain that is not &"kr"&. The local part is captured
5732 in &$1$& and the &"ac"& or &"edu"& in &$2$&.
5739 . ////////////////////////////////////////////////////////////////////////////
5740 . ////////////////////////////////////////////////////////////////////////////
5742 .chapter "File and database lookups" "CHAPfdlookup"
5743 .scindex IIDfidalo1 "file" "lookups"
5744 .scindex IIDfidalo2 "database lookups"
5745 .cindex "lookup" "description of"
5746 Exim can be configured to look up data in files or databases as it processes
5747 messages. Two different kinds of syntax are used:
5750 A string that is to be expanded may contain explicit lookup requests. These
5751 cause parts of the string to be replaced by data that is obtained from the
5752 lookup. Lookups of this type are conditional expansion items. Different results
5753 can be defined for the cases of lookup success and failure. See chapter
5754 &<<CHAPexpand>>&, where string expansions are described in detail.
5756 Lists of domains, hosts, and email addresses can contain lookup requests as a
5757 way of avoiding excessively long linear lists. In this case, the data that is
5758 returned by the lookup is often (but not always) discarded; whether the lookup
5759 succeeds or fails is what really counts. These kinds of list are described in
5760 chapter &<<CHAPdomhosaddlists>>&.
5763 String expansions, lists, and lookups interact with each other in such a way
5764 that there is no order in which to describe any one of them that does not
5765 involve references to the others. Each of these three chapters makes more sense
5766 if you have read the other two first. If you are reading this for the first
5767 time, be aware that some of it will make a lot more sense after you have read
5768 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
5770 .section "Examples of different lookup syntax"
5771 It is easy to confuse the two different kinds of lookup, especially as the
5772 lists that may contain the second kind are always expanded before being
5773 processed as lists. Therefore, they may also contain lookups of the first kind.
5774 Be careful to distinguish between the following two examples:
5776 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
5777 domains = lsearch;/some/file
5779 The first uses a string expansion, the result of which must be a domain list.
5780 No strings have been specified for a successful or a failing lookup; the
5781 defaults in this case are the looked-up data and an empty string, respectively.
5782 The expansion takes place before the string is processed as a list, and the
5783 file that is searched could contain lines like this:
5785 192.168.3.4: domain1:domain2:...
5786 192.168.1.9: domain3:domain4:...
5788 When the lookup succeeds, the result of the expansion is a list of domains (and
5789 possibly other types of item that are allowed in domain lists).
5791 In the second example, the lookup is a single item in a domain list. It causes
5792 Exim to use a lookup to see if the domain that is being processed can be found
5793 in the file. The file could contains lines like this:
5798 Any data that follows the keys is not relevant when checking that the domain
5799 matches the list item.
5801 It is possible, though no doubt confusing, to use both kinds of lookup at once.
5802 Consider a file containing lines like this:
5804 192.168.5.6: lsearch;/another/file
5806 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
5807 first &%domains%& setting above generates the second setting, which therefore
5808 causes a second lookup to occur.
5810 The rest of this chapter describes the different lookup types that are
5811 available. Any of them can be used in any part of the configuration where a
5812 lookup is permitted.
5815 .section "Lookup types"
5816 .cindex "lookup" "types of"
5817 .cindex "single-key lookup" "definition of"
5818 Two different types of data lookup are implemented:
5821 The &'single-key'& type requires the specification of a file in which to look,
5822 and a single key to search for. The key must be a non-empty string for the
5823 lookup to succeed. The lookup type determines how the file is searched.
5825 .cindex "query-style lookup" "definition of"
5826 The &'query-style'& type accepts a generalized database query. No particular
5827 key value is assumed by Exim for query-style lookups. You can use whichever
5828 Exim variables you need to construct the database query.
5831 The code for each lookup type is in a separate source file that is included in
5832 the binary of Exim only if the corresponding compile-time option is set. The
5833 default settings in &_src/EDITME_& are:
5838 which means that only linear searching and DBM lookups are included by default.
5839 For some types of lookup (e.g. SQL databases), you need to install appropriate
5840 libraries and header files before building Exim.
5845 .section "Single-key lookup types" "SECTsinglekeylookups"
5846 .cindex "lookup" "single-key types"
5847 .cindex "single-key lookup" "list of types"
5848 The following single-key lookup types are implemented:
5851 .cindex "cdb" "description of"
5852 .cindex "lookup" "cdb"
5853 .cindex "binary zero" "in lookup key"
5854 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
5855 string without a terminating binary zero. The cdb format is designed for
5856 indexed files that are read frequently and never updated, except by total
5857 re-creation. As such, it is particulary suitable for large files containing
5858 aliases or other indexed data referenced by an MTA. Information about cdb can
5859 be found in several places:
5861 &url(http://www.pobox.com/~djb/cdb.html)
5862 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
5863 &url(http://packages.debian.org/stable/utils/freecdb.html)
5865 A cdb distribution is not needed in order to build Exim with cdb support,
5866 because the code for reading cdb files is included directly in Exim itself.
5867 However, no means of building or testing cdb files is provided with Exim, so
5868 you need to obtain a cdb distribution in order to do this.
5870 .cindex "DBM" "lookup type"
5871 .cindex "lookup" "dbm"
5872 .cindex "binary zero" "in lookup key"
5873 &(dbm)&: Calls to DBM library functions are used to extract data from the given
5874 DBM file by looking up the record with the given key. A terminating binary
5875 zero is included in the key that is passed to the DBM library. See section
5876 &<<SECTdb>>& for a discussion of DBM libraries.
5878 .cindex "Berkeley DB library" "file format"
5879 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
5880 when building DBM files using the &%exim_dbmbuild%& utility. However, when
5881 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
5882 the DB_UNKNOWN option. This enables it to handle any of the types of database
5883 that the library supports, and can be useful for accessing DBM files created by
5884 other applications. (For earlier DB versions, DB_HASH is always used.)
5886 .cindex "lookup" "dbmnz"
5887 .cindex "lookup" "dbm &-- terminating zero"
5888 .cindex "binary zero" "in lookup key"
5890 .cindex "&_/etc/userdbshadow.dat_&"
5891 .cindex "dmbnz lookup type"
5892 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
5893 is not included in the key that is passed to the DBM library. You may need this
5894 if you want to look up data in files that are created by or shared with some
5895 other application that does not use terminating zeros. For example, you need to
5896 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
5897 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
5898 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
5899 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
5901 .cindex "lookup" "dsearch"
5902 .cindex "dsearch lookup type"
5903 &(dsearch)&: The given file must be a directory; this is searched for a file
5904 whose name is the key. The key may not contain any forward slash characters.
5905 The result of a successful lookup is the name of the file. An example of how
5906 this lookup can be used to support virtual domains is given in section
5907 &<<SECTvirtualdomains>>&.
5909 .cindex "lookup" "iplsearch"
5910 .cindex "iplsearch lookup type"
5911 &(iplsearch)&: The given file is a text file containing keys and data. A key is
5912 terminated by a colon or white space or the end of the line. The keys in the
5913 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
5914 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
5915 being interpreted as a key terminator. For example:
5917 1.2.3.4: data for 1.2.3.4
5918 192.168.0.0/16 data for 192.168.0.0/16
5919 "abcd::cdab": data for abcd::cdab
5920 "abcd:abcd::/32" data for abcd:abcd::/32
5922 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
5923 file is searched linearly, using the CIDR masks where present, until a matching
5924 key is found. The first key that matches is used; there is no attempt to find a
5925 &"best"& match. Apart from the way the keys are matched, the processing for
5926 &(iplsearch)& is the same as for &(lsearch)&.
5928 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
5929 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
5930 lookup types support only literal keys.
5932 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
5933 the implicit key is the host's IP address rather than its name (see section
5934 &<<SECThoslispatsikey>>&).
5937 .cindex "linear search"
5938 .cindex "lookup" "lsearch"
5939 .cindex "lsearch lookup type"
5940 &(lsearch)&: The given file is a text file that is searched linearly for a
5941 line beginning with the search key, terminated by a colon or white space or the
5942 end of the line. The first occurrence that is found in the file is used. White
5943 space between the key and the colon is permitted. The remainder of the line,
5944 with leading and trailing white space removed, is the data. This can be
5945 continued onto subsequent lines by starting them with any amount of white
5946 space, but only a single space character is included in the data at such a
5947 junction. If the data begins with a colon, the key must be terminated by a
5952 Empty lines and lines beginning with # are ignored, even if they occur in the
5953 middle of an item. This is the traditional textual format of alias files. Note
5954 that the keys in an &(lsearch)& file are literal strings. There is no
5955 wildcarding of any kind.
5957 .cindex "lookup" "lsearch &-- colons in keys"
5958 .cindex "white space" "in lsearch key"
5959 In most &(lsearch)& files, keys are not required to contain colons or #
5960 characters, or white space. However, if you need this feature, it is available.
5961 If a key begins with a doublequote character, it is terminated only by a
5962 matching quote (or end of line), and the normal escaping rules apply to its
5963 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
5964 quoted keys (exactly as for unquoted keys). There is no special handling of
5965 quotes for the data part of an &(lsearch)& line.
5968 .cindex "NIS lookup type"
5969 .cindex "lookup" "NIS"
5970 .cindex "binary zero" "in lookup key"
5971 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
5972 the given key, without a terminating binary zero. There is a variant called
5973 &(nis0)& which does include the terminating binary zero in the key. This is
5974 reportedly needed for Sun-style alias files. Exim does not recognize NIS
5975 aliases; the full map names must be used.
5978 .cindex "wildlsearch lookup type"
5979 .cindex "lookup" "wildlsearch"
5980 .cindex "nwildlsearch lookup type"
5981 .cindex "lookup" "nwildlsearch"
5982 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
5983 &(lsearch)&, but instead of being interpreted as a literal string, each key in
5984 the file may be wildcarded. The difference between these two lookup types is
5985 that for &(wildlsearch)&, each key in the file is string-expanded before being
5986 used, whereas for &(nwildlsearch)&, no expansion takes place.
5988 Like &(lsearch)&, the testing is done case-insensitively. The following forms
5989 of wildcard are recognized:
5991 . ==== As this is a nested list, any displays it contains must be indented
5992 . ==== as otherwise they are too far to the left.
5995 The string may begin with an asterisk to mean &"ends with"&. For example:
5997 *.a.b.c data for anything.a.b.c
5998 *fish data for anythingfish
6001 The string may begin with a circumflex to indicate a regular expression. For
6002 example, for &(wildlsearch)&:
6004 ^\N\d+\.a\.b\N data for <digits>.a.b
6006 Note the use of &`\N`& to disable expansion of the contents of the regular
6007 expression. If you are using &(nwildlsearch)&, where the keys are not
6008 string-expanded, the equivalent entry is:
6010 ^\d+\.a\.b data for <digits>.a.b
6012 If the regular expression contains white space or colon characters, you must
6013 either quote it (see &(lsearch)& above), or represent these characters in other
6014 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6015 colon. This may be easier than quoting, because if you quote, you have to
6016 escape all the backslashes inside the quotes.
6018 &*Note*&: It is not possible to capture substrings in a regular expression
6019 match for later use, because the results of all lookups are cached. If a lookup
6020 is repeated, the result is taken from the cache, and no actual pattern matching
6021 takes place. The values of all the numeric variables are unset after a
6022 &((n)wildlsearch)& match.
6025 Although I cannot see it being of much use, the general matching function that
6026 is used to implement &((n)wildlsearch)& means that the string may begin with a
6027 lookup name terminated by a semicolon, and followed by lookup data. For
6030 cdb;/some/file data for keys that match the file
6032 The data that is obtained from the nested lookup is discarded.
6035 Keys that do not match any of these patterns are interpreted literally. The
6036 continuation rules for the data are the same as for &(lsearch)&, and keys may
6037 be followed by optional colons.
6039 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6040 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6041 lookup types support only literal keys.
6045 .section "Query-style lookup types"
6046 .cindex "lookup" "query-style types"
6047 .cindex "query-style lookup" "list of types"
6048 The supported query-style lookup types are listed below. Further details about
6049 many of them are given in later sections.
6052 .cindex "DNS" "as a lookup type"
6053 .cindex "lookup" "DNS"
6054 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6055 are given in the supplied query. The resulting data is the contents of the
6056 records. See section &<<SECTdnsdb>>&.
6058 .cindex "Interbase lookup type"
6059 .cindex "lookup" "Interbase"
6060 &(ibase)&: This does a lookup in an Interbase database.
6062 .cindex "LDAP" "lookup type"
6063 .cindex "lookup" "LDAP"
6064 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6065 returns attributes from a single entry. There is a variant called &(ldapm)&
6066 that permits values from multiple entries to be returned. A third variant
6067 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6068 any attribute values. See section &<<SECTldap>>&.
6070 .cindex "MySQL" "lookup type"
6071 .cindex "lookup" "MySQL"
6072 &(mysql)&: The format of the query is an SQL statement that is passed to a
6073 MySQL database. See section &<<SECTsql>>&.
6075 .cindex "NIS+ lookup type"
6076 .cindex "lookup" "NIS+"
6077 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6078 the field to be returned. See section &<<SECTnisplus>>&.
6080 .cindex "Oracle" "lookup type"
6081 .cindex "lookup" "Oracle"
6082 &(oracle)&: The format of the query is an SQL statement that is passed to an
6083 Oracle database. See section &<<SECTsql>>&.
6085 .cindex "lookup" "passwd"
6086 .cindex "passwd lookup type"
6087 .cindex "&_/etc/passwd_&"
6088 &(passwd)& is a query-style lookup with queries that are just user names. The
6089 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6090 success, the result string is the same as you would get from an &(lsearch)&
6091 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6092 password value. For example:
6094 *:42:42:King Rat:/home/kr:/bin/bash
6097 .cindex "PostgreSQL lookup type"
6098 .cindex "lookup" "PostgreSQL"
6099 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6100 PostgreSQL database. See section &<<SECTsql>>&.
6103 .cindex "sqlite lookup type"
6104 .cindex "lookup" "sqlite"
6105 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6106 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6109 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6110 not likely to be useful in normal operation.
6112 .cindex "whoson lookup type"
6113 .cindex "lookup" "whoson"
6114 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a proposed
6115 Internet protocol that allows Internet server programs to check whether a
6116 particular (dynamically allocated) IP address is currently allocated to a known
6117 (trusted) user and, optionally, to obtain the identity of the said user. In
6118 Exim, this can be used to implement &"POP before SMTP"& checking using ACL
6121 require condition = \
6122 ${lookup whoson {$sender_host_address}{yes}{no}}
6124 The query consists of a single IP address. The value returned is the name of
6125 the authenticated user, which is stored in the variable &$value$&. However, in
6126 this example, the data in &$value$& is not used; the result of the lookup is
6127 one of the fixed strings &"yes"& or &"no"&.
6132 .section "Temporary errors in lookups"
6133 .cindex "lookup" "temporary error in"
6134 Lookup functions can return temporary error codes if the lookup cannot be
6135 completed. For example, an SQL or LDAP database might be unavailable. For this
6136 reason, it is not advisable to use a lookup that might do this for critical
6137 options such as a list of local domains.
6139 When a lookup cannot be completed in a router or transport, delivery
6140 of the message (to the relevant address) is deferred, as for any other
6141 temporary error. In other circumstances Exim may assume the lookup has failed,
6142 or may give up altogether.
6146 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6147 .cindex "wildcard lookups"
6148 .cindex "lookup" "default values"
6149 .cindex "lookup" "wildcard"
6150 .cindex "lookup" "* added to type"
6151 .cindex "default" "in single-key lookups"
6152 In this context, a &"default value"& is a value specified by the administrator
6153 that is to be used if a lookup fails.
6155 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6156 and the initial lookup fails, the key &"*"& is looked up in the file to
6157 provide a default value. See also the section on partial matching below.
6159 .cindex "*@ with single-key lookup"
6160 .cindex "lookup" "*@ added to type"
6161 .cindex "alias file" "per-domain default"
6162 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6163 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6164 character, a second lookup is done with everything before the last @ replaced
6165 by *. This makes it possible to provide per-domain defaults in alias files
6166 that include the domains in the keys. If the second lookup fails (or doesn't
6167 take place because there is no @ in the key), &"*"& is looked up.
6168 For example, a &(redirect)& router might contain:
6170 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6172 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6173 looks up these keys, in this order:
6179 The data is taken from whichever key it finds first. &*Note*&: In an
6180 &(lsearch)& file, this does not mean the first of these keys in the file. A
6181 complete scan is done for each key, and only if it is not found at all does
6182 Exim move on to try the next key.
6186 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6187 .cindex "partial matching"
6188 .cindex "wildcard lookups"
6189 .cindex "lookup" "partial matching"
6190 .cindex "lookup" "wildcard"
6191 .cindex "asterisk" "in search type"
6192 The normal operation of a single-key lookup is to search the file for an exact
6193 match with the given key. However, in a number of situations where domains are
6194 being looked up, it is useful to be able to do partial matching. In this case,
6195 information in the file that has a key starting with &"*."& is matched by any
6196 domain that ends with the components that follow the full stop. For example, if
6197 a key in a DBM file is
6199 *.dates.fict.example
6201 then when partial matching is enabled this is matched by (amongst others)
6202 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6203 by &'dates.fict.example'&, if that does not appear as a separate key in the
6206 &*Note*&: Partial matching is not available for query-style lookups. It is
6207 also not available for any lookup items in address lists (see section
6208 &<<SECTaddresslist>>&).
6210 Partial matching is implemented by doing a series of separate lookups using
6211 keys constructed by modifying the original subject key. This means that it can
6212 be used with any of the single-key lookup types, provided that
6213 partial matching keys
6214 beginning with a special prefix (default &"*."&) are included in the data file.
6215 Keys in the file that do not begin with the prefix are matched only by
6216 unmodified subject keys when partial matching is in use.
6218 Partial matching is requested by adding the string &"partial-"& to the front of
6219 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6220 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6221 is added at the start of the subject key, and it is looked up again. If that
6222 fails, further lookups are tried with dot-separated components removed from the
6223 start of the subject key, one-by-one, and &"*."& added on the front of what
6226 A minimum number of two non-* components are required. This can be adjusted
6227 by including a number before the hyphen in the search type. For example,
6228 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6229 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6230 subject key is &'2250.dates.fict.example'& then the following keys are looked
6231 up when the minimum number of non-* components is two:
6233 2250.dates.fict.example
6234 *.2250.dates.fict.example
6235 *.dates.fict.example
6238 As soon as one key in the sequence is successfully looked up, the lookup
6241 .cindex "lookup" "partial matching &-- changing prefix"
6242 .cindex "prefix" "for partial matching"
6243 The use of &"*."& as the partial matching prefix is a default that can be
6244 changed. The motivation for this feature is to allow Exim to operate with file
6245 formats that are used by other MTAs. A different prefix can be supplied in
6246 parentheses instead of the hyphen after &"partial"&. For example:
6248 domains = partial(.)lsearch;/some/file
6250 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6251 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6252 components is unchanged). The prefix may consist of any punctuation characters
6253 other than a closing parenthesis. It may be empty, for example:
6255 domains = partial1()cdb;/some/file
6257 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6258 &`a.b.c`&, &`b.c`&, and &`c`&.
6260 If &"partial0"& is specified, what happens at the end (when the lookup with
6261 just one non-wild component has failed, and the original key is shortened right
6262 down to the null string) depends on the prefix:
6265 If the prefix has zero length, the whole lookup fails.
6267 If the prefix has length 1, a lookup for just the prefix is done. For
6268 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6270 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6271 remainder is looked up. With the default prefix, therefore, the final lookup is
6272 for &"*"& on its own.
6274 Otherwise, the whole prefix is looked up.
6278 If the search type ends in &"*"& or &"*@"& (see section
6279 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6280 this implies happens after all partial lookups have failed. If &"partial0"& is
6281 specified, adding &"*"& to the search type has no effect with the default
6282 prefix, because the &"*"& key is already included in the sequence of partial
6283 lookups. However, there might be a use for lookup types such as
6284 &"partial0(.)lsearch*"&.
6286 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6287 in domain lists and the like. Partial matching works only in terms of
6288 dot-separated components; a key such as &`*fict.example`&
6289 in a database file is useless, because the asterisk in a partial matching
6290 subject key is always followed by a dot.
6295 .section "Lookup caching"
6296 .cindex "lookup" "caching"
6297 .cindex "caching" "lookup data"
6298 Exim caches all lookup results in order to avoid needless repetition of
6299 lookups. However, because (apart from the daemon) Exim operates as a collection
6300 of independent, short-lived processes, this caching applies only within a
6301 single Exim process. There is no inter-process lookup caching facility.
6303 For single-key lookups, Exim keeps the relevant files open in case there is
6304 another lookup that needs them. In some types of configuration this can lead to
6305 many files being kept open for messages with many recipients. To avoid hitting
6306 the operating system limit on the number of simultaneously open files, Exim
6307 closes the least recently used file when it needs to open more files than its
6308 own internal limit, which can be changed via the &%lookup_open_max%& option.
6310 The single-key lookup files are closed and the lookup caches are flushed at
6311 strategic points during delivery &-- for example, after all routing is
6317 .section "Quoting lookup data"
6318 .cindex "lookup" "quoting"
6319 .cindex "quoting" "in lookups"
6320 When data from an incoming message is included in a query-style lookup, there
6321 is the possibility of special characters in the data messing up the syntax of
6322 the query. For example, a NIS+ query that contains
6326 will be broken if the local part happens to contain a closing square bracket.
6327 For NIS+, data can be enclosed in double quotes like this:
6329 [name="$local_part"]
6331 but this still leaves the problem of a double quote in the data. The rule for
6332 NIS+ is that double quotes must be doubled. Other lookup types have different
6333 rules, and to cope with the differing requirements, an expansion operator
6334 of the following form is provided:
6336 ${quote_<lookup-type>:<string>}
6338 For example, the safest way to write the NIS+ query is
6340 [name="${quote_nisplus:$local_part}"]
6342 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6343 operator can be used for all lookup types, but has no effect for single-key
6344 lookups, since no quoting is ever needed in their key strings.
6349 .section "More about dnsdb" "SECTdnsdb"
6350 .cindex "dnsdb lookup"
6351 .cindex "lookup" "dnsdb"
6352 .cindex "DNS" "as a lookup type"
6353 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6354 of a record type and a domain name, separated by an equals sign. For example,
6355 an expansion string could contain:
6357 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6359 If the lookup succeeds, the result is placed in &$value$&, which in this case
6360 is used on its own as the result. If the lookup succeeds, the &`fail`& keyword
6361 causes a &'forced expansion failure'& &-- see section &<<SECTforexpfai>>& for
6362 an explanation of what this means.
6364 The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and,
6365 when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6366 configured). If no type is given, TXT is assumed. When the type is PTR,
6367 the data can be an IP address, written as normal; inversion and the addition of
6368 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6370 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6372 If the data for a PTR record is not a syntactically valid IP address, it is not
6373 altered and nothing is added.
6375 .cindex "MX record" "in &(dnsdb)& lookup"
6376 .cindex "SRV record" "in &(dnsdb)& lookup"
6377 For an MX lookup, both the preference value and the host name are returned for
6378 each record, separated by a space. For an SRV lookup, the priority, weight,
6379 port, and host name are returned for each record, separated by spaces.
6381 For any record type, if multiple records are found (or, for A6 lookups, if a
6382 single record leads to multiple addresses), the data is returned as a
6383 concatenation, with newline as the default separator. The order, of course,
6384 depends on the DNS resolver. You can specify a different separator character
6385 between multiple records by putting a right angle-bracket followed immediately
6386 by the new separator at the start of the query. For example:
6388 ${lookup dnsdb{>: a=host1.example}}
6390 It is permitted to specify a space as the separator character. Further
6391 white space is ignored.
6393 .section "Pseudo dnsdb record types"
6394 .cindex "MX record" "in &(dnsdb)& lookup"
6395 By default, both the preference value and the host name are returned for
6396 each MX record, separated by a space. If you want only host names, you can use
6397 the pseudo-type MXH:
6399 ${lookup dnsdb{mxh=a.b.example}}
6401 In this case, the preference values are omitted, and just the host names are
6404 .cindex "name server" "for enclosing domain"
6405 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6406 records on the given domain, but if none are found, it removes the first
6407 component of the domain name, and tries again. This process continues until NS
6408 records are found or there are no more components left (or there is a DNS
6409 error). In other words, it may return the name servers for a top-level domain,
6410 but it never returns the root name servers. If there are no NS records for the
6411 top-level domain, the lookup fails. Consider these examples:
6413 ${lookup dnsdb{zns=xxx.quercite.com}}
6414 ${lookup dnsdb{zns=xxx.edu}}
6416 Assuming that in each case there are no NS records for the full domain name,
6417 the first returns the name servers for &%quercite.com%&, and the second returns
6418 the name servers for &%edu%&.
6420 You should be careful about how you use this lookup because, unless the
6421 top-level domain does not exist, the lookup always returns some host names. The
6422 sort of use to which this might be put is for seeing if the name servers for a
6423 given domain are on a blacklist. You can probably assume that the name servers
6424 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6427 .cindex "CSA" "in &(dnsdb)& lookup"
6428 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6429 records according to the CSA rules, which are described in section
6430 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6431 not sufficient because of the extra parent domain search behaviour of CSA. The
6432 result of a successful lookup such as:
6434 ${lookup dnsdb {csa=$sender_helo_name}}
6436 has two space-separated fields: an authorization code and a target host name.
6437 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6438 authorization required but absent, or &"?"& for unknown.
6441 .section "Multiple dnsdb lookups"
6442 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6443 However, you can specify a list of domains or IP addresses in a single
6444 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6445 the default separator, but with the ability to change this. For example:
6447 ${lookup dnsdb{one.domain.com:two.domain.com}}
6448 ${lookup dnsdb{a=one.host.com:two.host.com}}
6449 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6451 In order to retain backwards compatibility, there is one special case: if
6452 the lookup type is PTR and no change of separator is specified, Exim looks
6453 to see if the rest of the string is precisely one IPv6 address. In this
6454 case, it does not treat it as a list.
6456 The data from each lookup is concatenated, with newline separators by default,
6457 in the same way that multiple DNS records for a single item are handled. A
6458 different separator can be specified, as described above.
6460 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6461 temporary DNS error for any of them, the behaviour is controlled by
6462 an optional keyword followed by a comma that may appear before the record
6463 type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
6464 &"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
6465 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6466 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6467 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6468 error causes the whole lookup to defer only if none of the other lookups
6469 succeed. The default is &"lax"&, so the following lookups are equivalent:
6471 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6472 ${lookup dnsdb{a=one.host.com:two.host.com}}
6474 Thus, in the default case, as long as at least one of the DNS lookups
6475 yields some data, the lookup succeeds.
6480 .section "More about LDAP" "SECTldap"
6481 .cindex "LDAP lookup"
6482 .cindex "lookup" "LDAP"
6483 .cindex "Solaris" "LDAP"
6484 The original LDAP implementation came from the University of Michigan; this has
6485 become &"Open LDAP"&, and there are now two different releases. Another
6486 implementation comes from Netscape, and Solaris 7 and subsequent releases
6487 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6488 the lookup function level, their error handling is different. For this reason
6489 it is necessary to set a compile-time variable when building Exim with LDAP, to
6490 indicate which LDAP library is in use. One of the following should appear in
6491 your &_Local/Makefile_&:
6493 LDAP_LIB_TYPE=UMICHIGAN
6494 LDAP_LIB_TYPE=OPENLDAP1
6495 LDAP_LIB_TYPE=OPENLDAP2
6496 LDAP_LIB_TYPE=NETSCAPE
6497 LDAP_LIB_TYPE=SOLARIS
6499 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
6500 same interface as the University of Michigan version.
6502 There are three LDAP lookup types in Exim. These behave slightly differently in
6503 the way they handle the results of a query:
6506 &(ldap)& requires the result to contain just one entry; if there are more, it
6509 &(ldapdn)& also requires the result to contain just one entry, but it is the
6510 Distinguished Name that is returned rather than any attribute values.
6512 &(ldapm)& permits the result to contain more than one entry; the attributes
6513 from all of them are returned.
6517 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
6518 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6519 the data returned by a successful lookup is described in the next section.
6520 First we explain how LDAP queries are coded.
6523 .section "Format of LDAP queries" "SECTforldaque"
6524 .cindex "LDAP" "query format"
6525 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6526 the configuration of a &(redirect)& router one might have this setting:
6528 data = ${lookup ldap \
6529 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6530 c=UK?mailbox?base?}}
6532 .cindex "LDAP" "with TLS"
6533 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
6534 secure (encrypted) LDAP connections. The second of these ensures that an
6535 encrypted TLS connection is used.
6538 .section "LDAP quoting"
6539 .cindex "LDAP" "quoting"
6540 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6541 and the second because the LDAP query is represented as a URL. Furthermore,
6542 within an LDAP query, two different kinds of quoting are required. For this
6543 reason, there are two different LDAP-specific quoting operators.
6545 The &%quote_ldap%& operator is designed for use on strings that are part of
6546 filter specifications. Conceptually, it first does the following conversions on
6554 in accordance with RFC 2254. The resulting string is then quoted according
6555 to the rules for URLs, that is, all non-alphanumeric characters except
6559 are converted to their hex values, preceded by a percent sign. For example:
6561 ${quote_ldap: a(bc)*, a<yz>; }
6565 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6567 Removing the URL quoting, this is (with a leading and a trailing space):
6569 a\28bc\29\2A, a<yz>;
6571 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
6572 base DN specifications in queries. Conceptually, it first converts the string
6573 by inserting a backslash in front of any of the following characters:
6577 It also inserts a backslash before any leading spaces or # characters, and
6578 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6579 is then quoted according to the rules for URLs. For example:
6581 ${quote_ldap_dn: a(bc)*, a<yz>; }
6585 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6587 Removing the URL quoting, this is (with a trailing space):
6589 \ a(bc)*\, a\<yz\>\;\
6591 There are some further comments about quoting in the section on LDAP
6592 authentication below.
6595 .section "LDAP connections"
6596 .cindex "LDAP" "connections"
6597 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6598 is in use, via a Unix domain socket. The example given above does not specify
6599 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6602 ldap://<hostname>:<port>/...
6604 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6605 used. When no server is specified in a query, a list of default servers is
6606 taken from the &%ldap_default_servers%& configuration option. This supplies a
6607 colon-separated list of servers which are tried in turn until one successfully
6608 handles a query, or there is a serious error. Successful handling either
6609 returns the requested data, or indicates that it does not exist. Serious errors
6610 are syntactical, or multiple values when only a single value is expected.
6611 Errors which cause the next server to be tried are connection failures, bind
6612 failures, and timeouts.
6614 For each server name in the list, a port number can be given. The standard way
6615 of specifing a host and port is to use a colon separator (RFC 1738). Because
6616 &%ldap_default_servers%& is a colon-separated list, such colons have to be
6617 doubled. For example
6619 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6621 If &%ldap_default_servers%& is unset, a URL with no server name is passed
6622 to the LDAP library with no server name, and the library's default (normally
6623 the local host) is used.
6625 If you are using the OpenLDAP library, you can connect to an LDAP server using
6626 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6627 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
6628 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6631 For this type of connection, instead of a host name for the server, a pathname
6632 for the socket is required, and the port number is not relevant. The pathname
6633 can be specified either as an item in &%ldap_default_servers%&, or inline in
6634 the query. In the former case, you can have settings such as
6636 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6638 When the pathname is given in the query, you have to escape the slashes as
6639 &`%2F`& to fit in with the LDAP URL syntax. For example:
6641 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6643 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
6644 a pathname, it uses the Unix domain socket code, even if the query actually
6645 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
6646 socket connection. This behaviour means that you can use a setting of
6647 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
6648 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
6649 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6652 If an explicit &`ldapi`& type is given in a query when a host name is
6653 specified, an error is diagnosed. However, if there are more items in
6654 &%ldap_default_servers%&, they are tried. In other words:
6657 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
6660 Using &`ldapi`& with a host name causes an error.
6664 Using &`ldapi`& with no host or path in the query, and no setting of
6665 &%ldap_default_servers%&, does whatever the library does by default.
6669 .section "LDAP authentication and control information"
6670 .cindex "LDAP" "authentication"
6671 The LDAP URL syntax provides no way of passing authentication and other control
6672 information to the server. To make this possible, the URL in an LDAP query may
6673 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
6674 spaces. If a value contains spaces it must be enclosed in double quotes, and
6675 when double quotes are used, backslash is interpreted in the usual way inside
6676 them. The following names are recognized:
6678 &`DEREFERENCE`& set the dereferencing parameter
6679 &`NETTIME `& set a timeout for a network operation
6680 &`USER `& set the DN, for authenticating the LDAP bind
6681 &`PASS `& set the password, likewise
6682 &`SIZE `& set the limit for the number of entries returned
6683 &`TIME `& set the maximum waiting time for a query
6685 The value of the DEREFERENCE parameter must be one of the words &"never"&,
6686 &"searching"&, &"finding"&, or &"always"&.
6688 The name CONNECT is an obsolete name for NETTIME, retained for
6689 backwards compatibility. This timeout (specified as a number of seconds) is
6690 enforced from the client end for operations that can be carried out over a
6691 network. Specifically, it applies to network connections and calls to the
6692 &'ldap_result()'& function. If the value is greater than zero, it is used if
6693 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
6694 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
6695 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
6696 Netscape SDK; for OpenLDAP no action is taken.
6698 The TIME parameter (also a number of seconds) is passed to the server to
6699 set a server-side limit on the time taken to complete a search.
6702 Here is an example of an LDAP query in an Exim lookup that uses some of these
6703 values. This is a single line, folded to fit on the page:
6706 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6707 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6710 The encoding of spaces as &`%20`& is a URL thing which should not be done for
6711 any of the auxiliary data. Exim configuration settings that include lookups
6712 which contain password information should be preceded by &"hide"& to prevent
6713 non-admin users from using the &%-bP%& option to see their values.
6715 The auxiliary data items may be given in any order. The default is no
6716 connection timeout (the system timeout is used), no user or password, no limit
6717 on the number of entries returned, and no time limit on queries.
6719 When a DN is quoted in the USER= setting for LDAP authentication, Exim
6720 removes any URL quoting that it may contain before passing it LDAP. Apparently
6721 some libraries do this for themselves, but some do not. Removing the URL
6722 quoting has two advantages:
6725 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
6726 DNs as with DNs inside actual queries.
6728 It permits spaces inside USER= DNs.
6731 For example, a setting such as
6733 USER=cn=${quote_ldap_dn:$1}
6735 should work even if &$1$& contains spaces.
6737 Expanded data for the PASS= value should be quoted using the &%quote%&
6738 expansion operator, rather than the LDAP quote operators. The only reason this
6739 field needs quoting is to ensure that it conforms to the Exim syntax, which
6740 does not allow unquoted spaces. For example:
6744 The LDAP authentication mechanism can be used to check passwords as part of
6745 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
6750 .section "Format of data returned by LDAP"
6751 .cindex "LDAP" "returned data formats"
6752 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
6753 as a sequence of values, for example
6755 cn=manager, o=University of Cambridge, c=UK
6757 The &(ldap)& lookup type generates an error if more than one entry matches the
6758 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
6759 the result between the data from different entries. It is possible for multiple
6760 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
6761 you know that whatever values are returned all came from a single entry in the
6764 In the common case where you specify a single attribute in your LDAP query, the
6765 result is not quoted, and does not contain the attribute name. If the attribute
6766 has multiple values, they are separated by commas.
6768 If you specify multiple attributes, the result contains space-separated, quoted
6769 strings, each preceded by the attribute name and an equals sign. Within the
6770 quotes, the quote character, backslash, and newline are escaped with
6771 backslashes, and commas are used to separate multiple values for the attribute.
6772 Apart from the escaping, the string within quotes takes the same form as the
6773 output when a single attribute is requested. Specifying no attributes is the
6774 same as specifying all of an entry's attributes.
6776 Here are some examples of the output format. The first line of each pair is an
6777 LDAP query, and the second is the data that is returned. The attribute called
6778 &%attr1%& has two values, whereas &%attr2%& has only one value:
6780 ldap:///o=base?attr1?sub?(uid=fred)
6783 ldap:///o=base?attr2?sub?(uid=fred)
6786 ldap:///o=base?attr1,attr2?sub?(uid=fred)
6787 attr1="value1.1, value1.2" attr2="value two"
6789 ldap:///o=base??sub?(uid=fred)
6790 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
6792 The &%extract%& operator in string expansions can be used to pick out
6793 individual fields from data that consists of &'key'&=&'value'& pairs. You can
6794 make use of Exim's &%-be%& option to run expansion tests and thereby check the
6795 results of LDAP lookups.
6800 .section "More about NIS+" "SECTnisplus"
6801 .cindex "NIS+ lookup type"
6802 .cindex "lookup" "NIS+"
6803 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
6804 and field name. If this is given, the result of a successful query is the
6805 contents of the named field; otherwise the result consists of a concatenation
6806 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
6807 values containing spaces are quoted. For example, the query
6809 [name=mg1456],passwd.org_dir
6811 might return the string
6813 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
6814 home=/home/mg1456 shell=/bin/bash shadow=""
6816 (split over two lines here to fit on the page), whereas
6818 [name=mg1456],passwd.org_dir:gcos
6824 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
6825 for the given indexed key. The effect of the &%quote_nisplus%& expansion
6826 operator is to double any quote characters within the text.
6830 .section "SQL lookups" "SECTsql"
6831 .cindex "SQL lookup types"
6832 Exim can support lookups in Interbase, MySQL, Oracle, PostgreSQL, and SQLite
6833 databases. Queries for these databases contain SQL statements, so an example
6836 ${lookup mysql{select mailbox from users where id='userx'}\
6839 If the result of the query contains more than one field, the data for each
6840 field in the row is returned, preceded by its name, so the result of
6842 ${lookup pgsql{select home,name from users where id='userx'}\
6847 home=/home/userx name="Mister X"
6849 Empty values and values containing spaces are double quoted, with embedded
6850 quotes escaped by a backslash. If the result of the query contains just one
6851 field, the value is passed back verbatim, without a field name, for example:
6855 If the result of the query yields more than one row, it is all concatenated,
6856 with a newline between the data for each row.
6859 .section "More about MySQL, PostgreSQL, Oracle, and Interbase"
6860 .cindex "MySQL" "lookup type"
6861 .cindex "PostgreSQL lookup type"
6862 .cindex "lookup" "MySQL"
6863 .cindex "lookup" "PostgreSQL"
6864 .cindex "Oracle" "lookup type"
6865 .cindex "lookup" "Oracle"
6866 .cindex "Interbase lookup type"
6867 .cindex "lookup" "Interbase"
6868 If any MySQL, PostgreSQL, Oracle, or Interbase lookups are used, the
6869 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
6870 option (as appropriate) must be set to a colon-separated list of server
6871 information. Each item in the list is a slash-separated list of four items:
6872 host name, database name, user name, and password. In the case of Oracle, the
6873 host name field is used for the &"service name"&, and the database name field
6874 is not used and should be empty. For example:
6876 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
6878 Because password data is sensitive, you should always precede the setting with
6879 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
6880 option. Here is an example where two MySQL servers are listed:
6882 hide mysql_servers = localhost/users/root/secret:\
6883 otherhost/users/root/othersecret
6885 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
6886 because this is a colon-separated list, the colon has to be doubled. For each
6887 query, these parameter groups are tried in order until a connection and a query
6890 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
6891 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
6892 respectively, and the characters single-quote, double-quote, and backslash
6893 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
6894 addition, escapes the percent and underscore characters. This cannot be done
6895 for MySQL because these escapes are not recognized in contexts where these
6896 characters are not special.
6899 .section "Special MySQL features"
6900 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
6901 causes a connection to the server on the local host by means of a Unix domain
6902 socket. An alternate socket can be specified in parentheses. The full syntax of
6903 each item in &%mysql_servers%& is:
6905 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
6906 <&'user'&>/<&'password'&>
6908 Any of the three sub-parts of the first field can be omitted. For normal use on
6909 the local host it can be left blank or set to just &"localhost"&.
6911 No database need be supplied &-- but if it is absent here, it must be given in
6914 If a MySQL query is issued that does not request any data (an insert, update,
6915 or delete command), the result of the lookup is the number of rows affected.
6917 &*Warning*&: This can be misleading. If an update does not actually change
6918 anything (for example, setting a field to the value it already has), the result
6919 is zero because no rows are affected.
6922 .section "Special PostgreSQL features"
6923 PostgreSQL lookups can also use Unix domain socket connections to the database.
6924 This is usually faster and costs less CPU time than a TCP/IP connection.
6925 However it can be used only if the mail server runs on the same machine as the
6926 database server. A configuration line for PostgreSQL via Unix domain sockets
6929 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
6931 In other words, instead of supplying a host name, a path to the socket is
6932 given. The path name is enclosed in parentheses so that its slashes aren't
6933 visually confused with the delimiters for the other server parameters.
6935 If a PostgreSQL query is issued that does not request any data (an insert,
6936 update, or delete command), the result of the lookup is the number of rows
6939 .section "More about SQLite" "SECTsqlite"
6940 .cindex "lookup" "SQLite"
6941 .cindex "SQLite lookup type"
6942 SQLite is different to the other SQL lookups because a file name is required in
6943 addition to the SQL query. An SQLite database is a single file, and there is no
6944 daemon as in the other SQL databases. The interface to Exim requires the name
6945 of the file, as an absolute path, to be given at the start of the query. It is
6946 separated from the query by white space. This means that the path name cannot
6947 contain white space. Here is a lookup expansion example:
6949 ${lookup sqlite {/some/thing/sqlitedb \
6950 select name from aliases where id='userx';}}
6952 In a list, the syntax is similar. For example:
6954 domainlist relay_domains = sqlite;/some/thing/sqlitedb \
6955 select * from relays where ip='$sender_host_address';
6957 The only character affected by the &%quote_sqlite%& operator is a single
6958 quote, which it doubles.
6960 The SQLite library handles multiple simultaneous accesses to the database
6961 internally. Multiple readers are permitted, but only one process can
6962 update at once. Attempts to access the database while it is being updated
6963 are rejected after a timeout period, during which the SQLite library
6964 waits for the lock to be released. In Exim, the default timeout is set
6965 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
6971 . ////////////////////////////////////////////////////////////////////////////
6972 . ////////////////////////////////////////////////////////////////////////////
6974 .chapter "Domain, host, address, and local part lists" &&&
6975 "CHAPdomhosaddlists" &&&
6976 "Domain, host, and address lists"
6977 .scindex IIDdohoadli "lists of domains; hosts; etc."
6978 A number of Exim configuration options contain lists of domains, hosts,
6979 email addresses, or local parts. For example, the &%hold_domains%& option
6980 contains a list of domains whose delivery is currently suspended. These lists
6981 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
6982 arguments to expansion conditions such as &%match_domain%&.
6984 Each item in one of these lists is a pattern to be matched against a domain,
6985 host, email address, or local part, respectively. In the sections below, the
6986 different types of pattern for each case are described, but first we cover some
6987 general facilities that apply to all four kinds of list.
6991 .section "Expansion of lists"
6992 .cindex "expansion" "of lists"
6993 Each list is expanded as a single string before it is used. The result of
6994 expansion must be a list, possibly containing empty items, which is split up
6995 into separate items for matching. By default, colon is the separator character,
6996 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
6997 &<<SECTempitelis>>& for details of the list syntax; the second of these
6998 discusses the way to specify empty list items.
7001 If the string expansion is forced to fail, Exim behaves as if the item it is
7002 testing (domain, host, address, or local part) is not in the list. Other
7003 expansion failures cause temporary errors.
7005 If an item in a list is a regular expression, backslashes, dollars and possibly
7006 other special characters in the expression must be protected against
7007 misinterpretation by the string expander. The easiest way to do this is to use
7008 the &`\N`& expansion feature to indicate that the contents of the regular
7009 expression should not be expanded. For example, in an ACL you might have:
7011 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7012 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7014 The first item is a regular expression that is protected from expansion by
7015 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7016 senders based on the receiving domain.
7021 .section "Negated items in lists"
7022 .cindex "list" "negation"
7023 .cindex "negation" "in lists"
7024 Items in a list may be positive or negative. Negative items are indicated by a
7025 leading exclamation mark, which may be followed by optional white space. A list
7026 defines a set of items (domains, etc). When Exim processes one of these lists,
7027 it is trying to find out whether a domain, host, address, or local part
7028 (respectively) is in the set that is defined by the list. It works like this:
7030 The list is scanned from left to right. If a positive item is matched, the
7031 subject that is being checked is in the set; if a negative item is matched, the
7032 subject is not in the set. If the end of the list is reached without the
7033 subject having matched any of the patterns, it is in the set if the last item
7034 was a negative one, but not if it was a positive one. For example, the list in
7036 domainlist relay_domains = !a.b.c : *.b.c
7038 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7039 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7040 list is positive. However, if the setting were
7042 domainlist relay_domains = !a.b.c
7044 then all domains other than &'a.b.c'& would match because the last item in the
7045 list is negative. In other words, a list that ends with a negative item behaves
7046 as if it had an extra item &`:*`& on the end.
7048 Another way of thinking about positive and negative items in lists is to read
7049 the connector as &"or"& after a positive item and as &"and"& after a negative
7054 .section "File names in lists" "SECTfilnamlis"
7055 .cindex "list" "file name in"
7056 If an item in a domain, host, address, or local part list is an absolute file
7057 name (beginning with a slash character), each line of the file is read and
7058 processed as if it were an independent item in the list, except that further
7059 file names are not allowed,
7060 and no expansion of the data from the file takes place.
7061 Empty lines in the file are ignored, and the file may also contain comment
7065 For domain and host lists, if a # character appears anywhere in a line of the
7066 file, it and all following characters are ignored.
7068 Because local parts may legitimately contain # characters, a comment in an
7069 address list or local part list file is recognized only if # is preceded by
7070 white space or the start of the line. For example:
7072 not#comment@x.y.z # but this is a comment
7076 Putting a file name in a list has the same effect as inserting each line of the
7077 file as an item in the list (blank lines and comments excepted). However, there
7078 is one important difference: the file is read each time the list is processed,
7079 so if its contents vary over time, Exim's behaviour changes.
7081 If a file name is preceded by an exclamation mark, the sense of any match
7082 within the file is inverted. For example, if
7084 hold_domains = !/etc/nohold-domains
7086 and the file contains the lines
7091 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7092 any domain matching &`*.b.c`& is not.
7096 .section "An lsearch file is not an out-of-line list"
7097 As will be described in the sections that follow, lookups can be used in lists
7098 to provide indexed methods of checking list membership. There has been some
7099 confusion about the way &(lsearch)& lookups work in lists. Because
7100 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7101 sometimes thought that it is allowed to contain wild cards and other kinds of
7102 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7103 always fixed strings, just as for any other single-key lookup type.
7105 If you want to use a file to contain wild-card patterns that form part of a
7106 list, just give the file name on its own, without a search type, as described
7107 in the previous section.
7112 .section "Named lists" "SECTnamedlists"
7113 .cindex "named lists"
7114 .cindex "list" "named"
7115 A list of domains, hosts, email addresses, or local parts can be given a name
7116 which is then used to refer to the list elsewhere in the configuration. This is
7117 particularly convenient if the same list is required in several different
7118 places. It also allows lists to be given meaningful names, which can improve
7119 the readability of the configuration. For example, it is conventional to define
7120 a domain list called &'local_domains'& for all the domains that are handled
7121 locally on a host, using a configuration line such as
7123 domainlist local_domains = localhost:my.dom.example
7125 Named lists are referenced by giving their name preceded by a plus sign, so,
7126 for example, a router that is intended to handle local domains would be
7127 configured with the line
7129 domains = +local_domains
7131 The first router in a configuration is often one that handles all domains
7132 except the local ones, using a configuration with a negated item like this:
7136 domains = ! +local_domains
7137 transport = remote_smtp
7140 The four kinds of named list are created by configuration lines starting with
7141 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7142 respectively. Then there follows the name that you are defining, followed by an
7143 equals sign and the list itself. For example:
7145 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7146 addresslist bad_senders = cdb;/etc/badsenders
7148 A named list may refer to other named lists:
7150 domainlist dom1 = first.example : second.example
7151 domainlist dom2 = +dom1 : third.example
7152 domainlist dom3 = fourth.example : +dom2 : fifth.example
7154 &*Warning*&: If the last item in a referenced list is a negative one, the
7155 effect may not be what you intended, because the negation does not propagate
7156 out to the higher level. For example, consider:
7158 domainlist dom1 = !a.b
7159 domainlist dom2 = +dom1 : *.b
7161 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7162 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7163 means it matches the second list as well. The effect is not the same as
7165 domainlist dom2 = !a.b : *.b
7167 where &'x.y'& does not match. It's best to avoid negation altogether in
7168 referenced lists if you can.
7170 Named lists may have a performance advantage. When Exim is routing an
7171 address or checking an incoming message, it caches the result of tests on named
7172 lists. So, if you have a setting such as
7174 domains = +local_domains
7176 on several of your routers
7177 or in several ACL statements,
7178 the actual test is done only for the first one. However, the caching works only
7179 if there are no expansions within the list itself or any sublists that it
7180 references. In other words, caching happens only for lists that are known to be
7181 the same each time they are referenced.
7183 By default, there may be up to 16 named lists of each type. This limit can be
7184 extended by changing a compile-time variable. The use of domain and host lists
7185 is recommended for concepts such as local domains, relay domains, and relay
7186 hosts. The default configuration is set up like this.
7190 .section "Named lists compared with macros"
7191 .cindex "list" "named compared with macro"
7192 .cindex "macro" "compared with named list"
7193 At first sight, named lists might seem to be no different from macros in the
7194 configuration file. However, macros are just textual substitutions. If you
7197 ALIST = host1 : host2
7198 auth_advertise_hosts = !ALIST
7200 it probably won't do what you want, because that is exactly the same as
7202 auth_advertise_hosts = !host1 : host2
7204 Notice that the second host name is not negated. However, if you use a host
7207 hostlist alist = host1 : host2
7208 auth_advertise_hosts = ! +alist
7210 the negation applies to the whole list, and so that is equivalent to
7212 auth_advertise_hosts = !host1 : !host2
7216 .section "Named list caching"
7217 .cindex "list" "caching of named"
7218 .cindex "caching" "named lists"
7219 While processing a message, Exim caches the result of checking a named list if
7220 it is sure that the list is the same each time. In practice, this means that
7221 the cache operates only if the list contains no $ characters, which guarantees
7222 that it will not change when it is expanded. Sometimes, however, you may have
7223 an expanded list that you know will be the same each time within a given
7224 message. For example:
7226 domainlist special_domains = \
7227 ${lookup{$sender_host_address}cdb{/some/file}}
7229 This provides a list of domains that depends only on the sending host's IP
7230 address. If this domain list is referenced a number of times (for example,
7231 in several ACL lines, or in several routers) the result of the check is not
7232 cached by default, because Exim does not know that it is going to be the
7233 same list each time.
7235 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7236 cache the result anyway. For example:
7238 domainlist_cache special_domains = ${lookup{...
7240 If you do this, you should be absolutely sure that caching is going to do
7241 the right thing in all cases. When in doubt, leave it out.
7245 .section "Domain lists" "SECTdomainlist"
7246 .cindex "domain list" "patterns for"
7247 .cindex "list" "domain list"
7248 Domain lists contain patterns that are to be matched against a mail domain.
7249 The following types of item may appear in domain lists:
7252 .cindex "primary host name"
7253 .cindex "host name" "matched in domain list"
7254 .cindex "&%primary_hostname%&"
7255 .cindex "domain list" "matching primary host name"
7256 .cindex "@ in a domain list"
7257 If a pattern consists of a single @ character, it matches the local host name,
7258 as set by the &%primary_hostname%& option (or defaulted). This makes it
7259 possible to use the same configuration file on several different hosts that
7260 differ only in their names.
7262 .cindex "@[] in a domain list"
7263 .cindex "domain list" "matching local IP interfaces"
7264 .cindex "domain literal"
7265 If a pattern consists of the string &`@[]`& it matches any local IP interface
7266 address, enclosed in square brackets, as in an email address that contains a
7268 In today's Internet, the use of domain literals is controversial.
7271 .cindex "@mx_primary"
7272 .cindex "@mx_secondary"
7273 .cindex "domain list" "matching MX pointers to local host"
7274 If a pattern consists of the string &`@mx_any`& it matches any domain that
7275 has an MX record pointing to the local host or to any host that is listed in
7276 .cindex "&%hosts_treat_as_local%&"
7277 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7278 are similar, except that the first matches only when a primary MX target is the
7279 local host, and the second only when no primary MX target is the local host,
7280 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7281 preference value &-- there may of course be more than one of them.
7283 The MX lookup that takes place when matching a pattern of this type is
7284 performed with the resolver options for widening names turned off. Thus, for
7285 example, a single-component domain will &'not'& be expanded by adding the
7286 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7287 options of the &(dnslookup)& router for a discussion of domain widening.
7289 Sometimes you may want to ignore certain IP addresses when using one of these
7290 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7291 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7292 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7293 on a router). For example:
7295 domains = @mx_any/ignore=127.0.0.1
7297 This example matches any domain that has an MX record pointing to one of
7298 the local host's IP addresses other than 127.0.0.1.
7300 The list of IP addresses is in fact processed by the same code that processes
7301 host lists, so it may contain CIDR-coded network specifications and it may also
7302 contain negative items.
7304 Because the list of IP addresses is a sublist within a domain list, you have to
7305 be careful about delimiters if there is more than one address. Like any other
7306 list, the default delimiter can be changed. Thus, you might have:
7308 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7309 an.other.domain : ...
7311 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7312 involved, it is easiest to change the delimiter for the main list as well:
7314 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7315 an.other.domain ? ...
7318 .cindex "asterisk" "in domain list"
7319 .cindex "domain list" "asterisk in"
7320 .cindex "domain list" "matching &""ends with""&"
7321 If a pattern starts with an asterisk, the remaining characters of the pattern
7322 are compared with the terminating characters of the domain. The use of &"*"& in
7323 domain lists differs from its use in partial matching lookups. In a domain
7324 list, the character following the asterisk need not be a dot, whereas partial
7325 matching works only in terms of dot-separated components. For example, a domain
7326 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7330 .cindex "regular expressions" "in domain list"
7331 .cindex "domain list" "matching regular expression"
7332 If a pattern starts with a circumflex character, it is treated as a regular
7333 expression, and matched against the domain using a regular expression matching
7334 function. The circumflex is treated as part of the regular expression.
7335 References to descriptions of the syntax of regular expressions are given in
7336 chapter &<<CHAPregexp>>&.
7338 &*Warning*&: Because domain lists are expanded before being processed, you
7339 must escape any backslash and dollar characters in the regular expression, or
7340 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7341 it is not to be expanded (unless you really do want to build a regular
7342 expression by expansion, of course).
7344 .cindex "lookup" "in domain list"
7345 .cindex "domain list" "matching by lookup"
7346 If a pattern starts with the name of a single-key lookup type followed by a
7347 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7348 must be a file name in a suitable format for the lookup type. For example, for
7349 &"cdb;"& it must be an absolute path:
7351 domains = cdb;/etc/mail/local_domains.cdb
7353 The appropriate type of lookup is done on the file using the domain name as the
7354 key. In most cases, the data that is looked up is not used; Exim is interested
7355 only in whether or not the key is present in the file. However, when a lookup
7356 is used for the &%domains%& option on a router
7357 or a &%domains%& condition in an ACL statement, the data is preserved in the
7358 &$domain_data$& variable and can be referred to in other router options or
7359 other statements in the same ACL.
7362 Any of the single-key lookup type names may be preceded by
7363 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7365 domains = partial-dbm;/partial/domains
7367 This causes partial matching logic to be invoked; a description of how this
7368 works is given in section &<<SECTpartiallookup>>&.
7371 .cindex "asterisk" "in lookup type"
7372 Any of the single-key lookup types may be followed by an asterisk. This causes
7373 a default lookup for a key consisting of a single asterisk to be done if the
7374 original lookup fails. This is not a useful feature when using a domain list to
7375 select particular domains (because any domain would match), but it might have
7376 value if the result of the lookup is being used via the &$domain_data$&
7379 If the pattern starts with the name of a query-style lookup type followed by a
7380 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
7381 pattern must be an appropriate query for the lookup type, as described in
7382 chapter &<<CHAPfdlookup>>&. For example:
7384 hold_domains = mysql;select domain from holdlist \
7385 where domain = '$domain';
7387 In most cases, the data that is looked up is not used (so for an SQL query, for
7388 example, it doesn't matter what field you select). Exim is interested only in
7389 whether or not the query succeeds. However, when a lookup is used for the
7390 &%domains%& option on a router, the data is preserved in the &$domain_data$&
7391 variable and can be referred to in other options.
7393 .cindex "domain list" "matching literal domain name"
7394 If none of the above cases apply, a caseless textual comparison is made
7395 between the pattern and the domain.
7398 Here is an example that uses several different kinds of pattern:
7400 domainlist funny_domains = \
7403 *.foundation.fict.example : \
7404 \N^[1-2]\d{3}\.fict\.example$\N : \
7405 partial-dbm;/opt/data/penguin/book : \
7406 nis;domains.byname : \
7407 nisplus;[name=$domain,status=local],domains.org_dir
7409 There are obvious processing trade-offs among the various matching modes. Using
7410 an asterisk is faster than a regular expression, and listing a few names
7411 explicitly probably is too. The use of a file or database lookup is expensive,
7412 but may be the only option if hundreds of names are required. Because the
7413 patterns are tested in order, it makes sense to put the most commonly matched
7418 .section "Host lists" "SECThostlist"
7419 .cindex "host list" "patterns in"
7420 .cindex "list" "host list"
7421 Host lists are used to control what remote hosts are allowed to do. For
7422 example, some hosts may be allowed to use the local host as a relay, and some
7423 may be permitted to use the SMTP ETRN command. Hosts can be identified in
7424 two different ways, by name or by IP address. In a host list, some types of
7425 pattern are matched to a host name, and some are matched to an IP address.
7426 You need to be particularly careful with this when single-key lookups are
7427 involved, to ensure that the right value is being used as the key.
7430 .section "Special host list patterns"
7431 .cindex "empty item in hosts list"
7432 .cindex "host list" "empty string in"
7433 If a host list item is the empty string, it matches only when no remote host is
7434 involved. This is the case when a message is being received from a local
7435 process using SMTP on the standard input, that is, when a TCP/IP connection is
7438 .cindex "asterisk" "in host list"
7439 The special pattern &"*"& in a host list matches any host or no host. Neither
7440 the IP address nor the name is actually inspected.
7444 .section "Host list patterns that match by IP address" "SECThoslispatip"
7445 .cindex "host list" "matching IP addresses"
7446 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7447 the incoming address actually appears in the IPv6 host as
7448 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
7449 list, it is converted into a traditional IPv4 address first. (Not all operating
7450 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7453 The following types of pattern in a host list check the remote host by
7454 inspecting its IP address:
7457 If the pattern is a plain domain name (not a regular expression, not starting
7458 with *, not a lookup of any kind), Exim calls the operating system function
7459 to find the associated IP address(es). Exim uses the newer
7460 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
7461 This typically causes a forward DNS lookup of the name. The result is compared
7462 with the IP address of the subject host.
7464 If there is a temporary problem (such as a DNS timeout) with the host name
7465 lookup, a temporary error occurs. For example, if the list is being used in an
7466 ACL condition, the ACL gives a &"defer"& response, usually leading to a
7467 temporary SMTP error code. If no IP address can be found for the host name,
7468 what happens is described in section &<<SECTbehipnot>>& below.
7471 .cindex "@ in a host list"
7472 If the pattern is &"@"&, the primary host name is substituted and used as a
7473 domain name, as just described.
7476 If the pattern is an IP address, it is matched against the IP address of the
7477 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
7478 IPv6 addresses can be given in colon-separated format, but the colons have to
7479 be doubled so as not to be taken as item separators when the default list
7480 separator is used. IPv6 addresses are recognized even when Exim is compiled
7481 without IPv6 support. This means that if they appear in a host list on an
7482 IPv4-only host, Exim will not treat them as host names. They are just addresses
7483 that can never match a client host.
7486 .cindex "@[] in a host list"
7487 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
7488 the local host. For example, if the local host is an IPv4 host with one
7489 interface address 10.45.23.56, these two ACL statements have the same effect:
7491 accept hosts = 127.0.0.1 : 10.45.23.56
7495 .cindex "CIDR notation"
7496 If the pattern is an IP address followed by a slash and a mask length (for
7497 example 10.11.42.0/24), it is matched against the IP address of the subject
7498 host under the given mask. This allows, an entire network of hosts to be
7499 included (or excluded) by a single item. The mask uses CIDR notation; it
7500 specifies the number of address bits that must match, starting from the most
7501 significant end of the address.
7503 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
7504 of a range of addresses. It is the number of bits in the network portion of the
7505 address. The above example specifies a 24-bit netmask, so it matches all 256
7506 addresses in the 10.11.42.0 network. An item such as
7510 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7511 32 for an IPv4 address is the same as no mask at all; just a single address
7514 Here is another example which shows an IPv4 and an IPv6 network:
7516 recipient_unqualified_hosts = 192.168.0.0/16: \
7517 3ffe::ffff::836f::::/48
7519 The doubling of list separator characters applies only when these items
7520 appear inline in a host list. It is not required when indirecting via a file.
7523 recipient_unqualified_hosts = /opt/exim/unqualnets
7525 could make use of a file containing
7530 to have exactly the same effect as the previous example. When listing IPv6
7531 addresses inline, it is usually more convenient to use the facility for
7532 changing separator characters. This list contains the same two networks:
7534 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7537 The separator is changed to semicolon by the leading &"<;"& at the start of the
7543 .section "Host list patterns for single-key lookups by host address" &&&
7544 "SECThoslispatsikey"
7545 .cindex "host list" "lookup of IP address"
7546 When a host is to be identified by a single-key lookup of its complete IP
7547 address, the pattern takes this form:
7549 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7553 hosts_lookup = net-cdb;/hosts-by-ip.db
7555 The text form of the IP address of the subject host is used as the lookup key.
7556 IPv6 addresses are converted to an unabbreviated form, using lower case
7557 letters, with dots as separators because colon is the key terminator in
7558 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
7559 quoting the keys, but this is a facility that was added later.] The data
7560 returned by the lookup is not used.
7562 .cindex "IP address" "masking"
7563 .cindex "host list" "masked IP address"
7564 Single-key lookups can also be performed using masked IP addresses, using
7565 patterns of this form:
7567 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7571 net24-dbm;/networks.db
7573 The IP address of the subject host is masked using <&'number'&> as the mask
7574 length. A textual string is constructed from the masked value, followed by the
7575 mask, and this is used as the lookup key. For example, if the host's IP address
7576 is 192.168.34.6, the key that is looked up for the above example is
7577 &"192.168.34.0/24"&. IPv6 addresses are converted to a text value using lower
7578 case letters and dots as separators instead of the more usual colon, because
7579 colon is the key terminator in &(lsearch)& files. Full, unabbreviated IPv6
7580 addresses are always used.
7582 &*Warning*&: Specifing &%net32-%& (for an IPv4 address) or &%net128-%& (for an
7583 IPv6 address) is not the same as specifing just &%net-%& without a number. In
7584 the former case the key strings include the mask value, whereas in the latter
7585 case the IP address is used on its own.
7589 .section "Host list patterns that match by host name" "SECThoslispatnam"
7590 .cindex "host" "lookup failures"
7591 .cindex "unknown host name"
7592 .cindex "host list" "matching host name"
7593 There are several types of pattern that require Exim to know the name of the
7594 remote host. These are either wildcard patterns or lookups by name. (If a
7595 complete hostname is given without any wildcarding, it is used to find an IP
7596 address to match against, as described in the section &<<SECThoslispatip>>&
7599 If the remote host name is not already known when Exim encounters one of these
7600 patterns, it has to be found from the IP address.
7601 Although many sites on the Internet are conscientious about maintaining reverse
7602 DNS data for their hosts, there are also many that do not do this.
7603 Consequently, a name cannot always be found, and this may lead to unwanted
7604 effects. Take care when configuring host lists with wildcarded name patterns.
7605 Consider what will happen if a name cannot be found.
7607 Because of the problems of determining host names from IP addresses, matching
7608 against host names is not as common as matching against IP addresses.
7610 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7611 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
7612 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
7613 are done can be changed by setting the &%host_lookup_order%& option.
7615 There are some options that control what happens if a host name cannot be
7616 found. These are described in section &<<SECTbehipnot>>& below.
7618 .cindex "host" "alias for"
7619 .cindex "alias for host"
7620 As a result of aliasing, hosts may have more than one name. When processing any
7621 of the following types of pattern, all the host's names are checked:
7624 .cindex "asterisk" "in host list"
7625 If a pattern starts with &"*"& the remainder of the item must match the end of
7626 the host name. For example, &`*.b.c`& matches all hosts whose names end in
7627 &'.b.c'&. This special simple form is provided because this is a very common
7628 requirement. Other kinds of wildcarding require the use of a regular
7631 .cindex "regular expressions" "in host list"
7632 .cindex "host list" "regular expression in"
7633 If the item starts with &"^"& it is taken to be a regular expression which is
7634 matched against the host name. For example,
7638 is a regular expression that matches either of the two hosts &'a.c.d'& or
7639 &'b.c.d'&. When a regular expression is used in a host list, you must take care
7640 that backslash and dollar characters are not misinterpreted as part of the
7641 string expansion. The simplest way to do this is to use &`\N`& to mark that
7642 part of the string as non-expandable. For example:
7644 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
7646 &*Warning*&: If you want to match a complete host name, you must include the
7647 &`$`& terminating metacharacter in the regular expression, as in the above
7648 example. Without it, a match at the start of the host name is all that is
7655 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
7656 .cindex "host" "lookup failures"
7657 While processing a host list, Exim may need to look up an IP address from a
7658 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
7659 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
7660 behaviour when it fails to find the information it is seeking is the same.
7662 .cindex "&`+include_unknown`&"
7663 .cindex "&`+ignore_unknown`&"
7664 By default, Exim behaves as if the host does not match the list. This may not
7665 always be what you want to happen. To change Exim's behaviour, the special
7666 items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at
7667 top level &-- they are not recognized in an indirected file).
7670 If any item that follows &`+include_unknown`& requires information that
7671 cannot found, Exim behaves as if the host does match the list. For example,
7673 host_reject_connection = +include_unknown:*.enemy.ex
7675 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
7676 any hosts whose name it cannot find.
7679 If any item that follows &`+ignore_unknown`& requires information that cannot
7680 be found, Exim ignores that item and proceeds to the rest of the list. For
7683 accept hosts = +ignore_unknown : friend.example : \
7686 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
7687 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
7688 name can be found for 192.168.4.5, it is rejected.
7691 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
7692 list. The effect of each one lasts until the next, or until the end of the
7696 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
7697 apply to temporary DNS errors. They always cause a defer action (except when
7698 &%dns_again_means_nonexist%& converts them into permanent errors).
7703 .section "Host list patterns for single-key lookups by host name" &&&
7704 "SECThoslispatnamsk"
7705 .cindex "host" "lookup failures"
7706 .cindex "unknown host name"
7707 .cindex "host list" "matching host name"
7708 If a pattern is of the form
7710 <&'single-key-search-type'&>;<&'search-data'&>
7714 dbm;/host/accept/list
7716 a single-key lookup is performend, using the host name as its key. If the
7717 lookup succeeds, the host matches the item. The actual data that is looked up
7720 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
7721 keys in the file, not IP addresses. If you want to do lookups based on IP
7722 addresses, you must precede the search type with &"net-"& (see section
7723 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
7724 two items in the same list, one doing an address lookup and one doing a name
7725 lookup, both using the same file.
7729 .section "Host list patterns for query-style lookups"
7730 If a pattern is of the form
7732 <&'query-style-search-type'&>;<&'query'&>
7734 the query is obeyed, and if it succeeds, the host matches the item. The actual
7735 data that is looked up is not used. The variables &$sender_host_address$& and
7736 &$sender_host_name$& can be used in the query. For example:
7738 hosts_lookup = pgsql;\
7739 select ip from hostlist where ip='$sender_host_address'
7741 The value of &$sender_host_address$& for an IPv6 address contains colons. You
7742 can use the &%sg%& expansion item to change this if you need to. If you want to
7743 use masked IP addresses in database queries, you can use the &%mask%& expansion
7746 If the query contains a reference to &$sender_host_name$&, Exim automatically
7747 looks up the host name if has not already done so. (See section
7748 &<<SECThoslispatnam>>& for comments on finding host names.)
7750 Historical note: prior to release 4.30, Exim would always attempt to find a
7751 host name before running the query, unless the search type was preceded by
7752 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
7753 still recognized for query-style lookups, but its presence or absence has no
7754 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
7755 See section &<<SECThoslispatsikey>>&.)
7759 .section "Mixing wildcarded host names and addresses in host lists" &&&
7761 .cindex "host list" "mixing names and addresses in"
7762 If you have name lookups or wildcarded host names and IP addresses in the same
7763 host list, you should normally put the IP addresses first. For example, in an
7766 accept hosts = 10.9.8.7 : *.friend.example
7768 The reason for this lies in the left-to-right way that Exim processes lists.
7769 It can test IP addresses without doing any DNS lookups, but when it reaches an
7770 item that requires a host name, it fails if it cannot find a host name to
7771 compare with the pattern. If the above list is given in the opposite order, the
7772 &%accept%& statement fails for a host whose name cannot be found, even if its
7773 IP address is 10.9.8.7.
7775 If you really do want to do the name check first, and still recognize the IP
7776 address, you can rewrite the ACL like this:
7778 accept hosts = *.friend.example
7779 accept hosts = 10.9.8.7
7781 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
7782 &<<CHAPACL>>& for details of ACLs.
7788 .section "Address lists" "SECTaddresslist"
7789 .cindex "list" "address list"
7790 .cindex "address list" "empty item"
7791 .cindex "address list" "patterns"
7792 Address lists contain patterns that are matched against mail addresses. There
7793 is one special case to be considered: the sender address of a bounce message is
7794 always empty. You can test for this by providing an empty item in an address
7795 list. For example, you can set up a router to process bounce messages by
7796 using this option setting:
7800 The presence of the colon creates an empty item. If you do not provide any
7801 data, the list is empty and matches nothing. The empty sender can also be
7802 detected by a regular expression that matches an empty string,
7803 and by a query-style lookup that succeeds when &$sender_address$& is empty.
7806 Non-empty items in an address list can be straightforward email addresses. For
7809 senders = jbc@askone.example : hs@anacreon.example
7811 A certain amount of wildcarding is permitted. If a pattern contains an @
7812 character, but is not a regular expression and does not begin with a
7813 semicolon-terminated lookup type (described below), the local part of the
7814 subject address is compared with the local part of the pattern, which may start
7815 with an asterisk. If the local parts match, the domain is checked in exactly
7816 the same way as for a pattern in a domain list. For example, the domain can be
7817 wildcarded, refer to a named list, or be a lookup:
7819 deny senders = *@*.spamming.site:\
7820 *@+hostile_domains:\
7821 bozo@partial-lsearch;/list/of/dodgy/sites:\
7822 *@dbm;/bad/domains.db
7824 .cindex "local part" "starting with !"
7825 .cindex "address list" "local part starting with !"
7826 If a local part that begins with an exclamation mark is required, it has to be
7827 specified using a regular expression, because otherwise the exclamation mark is
7828 treated as a sign of negation, as is standard in lists.
7830 If a non-empty pattern that is not a regular expression or a lookup does not
7831 contain an @ character, it is matched against the domain part of the subject
7832 address. The only two formats that are recognized this way are a literal
7833 domain, or a domain pattern that starts with *. In both these cases, the effect
7834 is the same as if &`*@`& preceded the pattern. For example:
7836 deny senders = enemy.domain : *.enemy.domain
7839 The following kinds of more complicated address list pattern can match any
7840 address, including the empty address that is characteristic of bounce message
7844 .cindex "regular expressions" "in address list"
7845 .cindex "address list" "regular expression in"
7846 If (after expansion) a pattern starts with &"^"&, a regular expression match is
7847 done against the complete address, with the pattern as the regular expression.
7848 You must take care that backslash and dollar characters are not misinterpreted
7849 as part of the string expansion. The simplest way to do this is to use &`\N`&
7850 to mark that part of the string as non-expandable. For example:
7852 deny senders = \N^.*this.*@example\.com$\N : \
7853 \N^\d{8}.+@spamhaus.example$\N : ...
7855 The &`\N`& sequences are removed by the expansion, so these items do indeed
7856 start with &"^"& by the time they are being interpreted as address patterns.
7860 .cindex "address list" "lookup for complete address"
7861 Complete addresses can be looked up by using a pattern that starts with a
7862 lookup type terminated by a semicolon, followed by the data for the lookup. For
7865 deny senders = cdb;/etc/blocked.senders : \
7866 mysql;select address from blocked where \
7867 address='${quote_mysql:$sender_address}'
7869 Both query-style and single-key lookup types can be used. For a single-key
7870 lookup type, Exim uses the complete address as the key. However, empty keys are
7871 not supported for single-key lookups, so a match against the empty address
7872 always fails. This restriction does not apply to query-style lookups.
7874 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
7875 cannot be used, and is ignored if specified, with an entry being written to the
7877 .cindex "*@ with single-key lookup"
7878 However, you can configure lookup defaults, as described in section
7879 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
7880 default. For example, with this lookup:
7882 accept senders = lsearch*@;/some/file
7884 the file could contains lines like this:
7886 user1@domain1.example
7889 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
7892 nimrod@jaeger.example
7896 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
7897 would mean that every address matches, thus rendering the test useless.
7899 &*Warning 2*&: Do not confuse these two kinds of item:
7901 deny recipients = dbm*@;/some/file
7902 deny recipients = *@dbm;/some/file
7904 The first does a whole address lookup, with defaulting, as just described,
7905 because it starts with a lookup type. The second matches the local part and
7906 domain independently, as described in a bullet point below.
7910 The following kinds of address list pattern can match only non-empty addresses.
7911 If the subject address is empty, a match against any of these pattern types
7916 .cindex "@@ with single-key lookup"
7917 .cindex "address list" "@@ lookup type"
7918 .cindex "address list" "split local part and domain"
7919 If a pattern starts with &"@@"& followed by a single-key lookup item
7920 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
7921 split into a local part and a domain. The domain is looked up in the file. If
7922 it is not found, there is no match. If it is found, the data that is looked up
7923 from the file is treated as a colon-separated list of local part patterns, each
7924 of which is matched against the subject local part in turn.
7926 .cindex "asterisk" "in address list"
7927 The lookup may be a partial one, and/or one involving a search for a default
7928 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
7929 patterns that are looked up can be regular expressions or begin with &"*"&, or
7930 even be further lookups. They may also be independently negated. For example,
7933 deny senders = @@dbm;/etc/reject-by-domain
7935 the data from which the DBM file is built could contain lines like
7937 baddomain.com: !postmaster : *
7939 to reject all senders except &%postmaster%& from that domain.
7941 .cindex "local part" "starting with !"
7942 If a local part that actually begins with an exclamation mark is required, it
7943 has to be specified using a regular expression. In &(lsearch)& files, an entry
7944 may be split over several lines by indenting the second and subsequent lines,
7945 but the separating colon must still be included at line breaks. White space
7946 surrounding the colons is ignored. For example:
7948 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
7951 As in all colon-separated lists in Exim, a colon can be included in an item by
7954 If the last item in the list starts with a right angle-bracket, the remainder
7955 of the item is taken as a new key to look up in order to obtain a continuation
7956 list of local parts. The new key can be any sequence of characters. Thus one
7957 might have entries like
7959 aol.com: spammer1 : spammer 2 : >*
7960 xyz.com: spammer3 : >*
7963 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
7964 local parts for all domains, in addition to the specific local parts listed for
7965 each domain. Of course, using this feature costs another lookup each time a
7966 chain is followed, but the effort needed to maintain the data is reduced.
7968 .cindex "loop" "in lookups"
7969 It is possible to construct loops using this facility, and in order to catch
7970 them, the chains may be no more than fifty items long.
7973 The @@<&'lookup'&> style of item can also be used with a query-style
7974 lookup, but in this case, the chaining facility is not available. The lookup
7975 can only return a single list of local parts.
7978 &*Warning*&: There is an important difference between the address list items
7979 in these two examples:
7982 senders = *@+my_list
7984 In the first one, &`my_list`& is a named address list, whereas in the second
7985 example it is a named domain list.
7990 .section "Case of letters in address lists" "SECTcasletadd"
7991 .cindex "case of local parts"
7992 .cindex "address list" "case forcing"
7993 .cindex "case forcing in address lists"
7994 Domains in email addresses are always handled caselessly, but for local parts
7995 case may be significant on some systems (see &%caseful_local_part%& for how
7996 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
7997 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
7998 blocking lists should be done in a case-independent manner. Since most address
7999 lists in Exim are used for this kind of control, Exim attempts to do this by
8002 The domain portion of an address is always lowercased before matching it to an
8003 address list. The local part is lowercased by default, and any string
8004 comparisons that take place are done caselessly. This means that the data in
8005 the address list itself, in files included as plain file names, and in any file
8006 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8007 keys in files that are looked up by a search type other than &(lsearch)& (which
8008 works caselessly) must be in lower case, because these lookups are not
8011 .cindex "&`+caseful`&"
8012 To allow for the possibility of caseful address list matching, if an item in
8013 an address list is the string &"+caseful"&, the original case of the local
8014 part is restored for any comparisons that follow, and string comparisons are no
8015 longer case-independent. This does not affect the domain, which remains in
8016 lower case. However, although independent matches on the domain alone are still
8017 performed caselessly, regular expressions that match against an entire address
8018 become case-sensitive after &"+caseful"& has been seen.
8022 .section "Local part lists" "SECTlocparlis"
8023 .cindex "list" "local part list"
8024 .cindex "local part" "list"
8025 Case-sensitivity in local part lists is handled in the same way as for address
8026 lists, as just described. The &"+caseful"& item can be used if required. In a
8027 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8028 set false, the subject is lowercased and the matching is initially
8029 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8030 matching in the local part list, but not elsewhere in the router. If
8031 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8032 option is case-sensitive from the start.
8034 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8035 comments are handled in the same way as address lists &-- they are recognized
8036 only if the # is preceded by white space or the start of the line.
8037 Otherwise, local part lists are matched in the same way as domain lists, except
8038 that the special items that refer to the local host (&`@`&, &`@[]`&,
8039 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8040 Refer to section &<<SECTdomainlist>>& for details of the other available item
8042 .ecindex IIDdohoadli
8047 . ////////////////////////////////////////////////////////////////////////////
8048 . ////////////////////////////////////////////////////////////////////////////
8050 .chapter "String expansions" "CHAPexpand"
8051 .scindex IIDstrexp "expansion" "of strings"
8052 Many strings in Exim's run time configuration are expanded before use. Some of
8053 them are expanded every time they are used; others are expanded only once.
8055 When a string is being expanded it is copied verbatim from left to right except
8056 when a dollar or backslash character is encountered. A dollar specifies the
8057 start of a portion of the string that is interpreted and replaced as described
8058 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8059 escape character, as described in the following section.
8063 .section "Literal text in expanded strings" "SECTlittext"
8064 .cindex "expansion" "including literal text"
8065 An uninterpreted dollar can be included in an expanded string by putting a
8066 backslash in front of it. A backslash can be used to prevent any special
8067 character being treated specially in an expansion, including backslash itself.
8068 If the string appears in quotes in the configuration file, two backslashes are
8069 required because the quotes themselves cause interpretation of backslashes when
8070 the string is read in (see section &<<SECTstrings>>&).
8072 .cindex "expansion" "non-expandable substrings"
8073 A portion of the string can specified as non-expandable by placing it between
8074 two occurrences of &`\N`&. This is particularly useful for protecting regular
8075 expressions, which often contain backslashes and dollar signs. For example:
8077 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8079 On encountering the first &`\N`&, the expander copies subsequent characters
8080 without interpretation until it reaches the next &`\N`& or the end of the
8085 .section "Character escape sequences in expanded strings"
8086 .cindex "expansion" "escape sequences"
8087 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8088 expanded string is recognized as an escape sequence for the character newline,
8089 carriage return, or tab, respectively. A backslash followed by up to three
8090 octal digits is recognized as an octal encoding for a single character, and a
8091 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8094 These escape sequences are also recognized in quoted strings when they are read
8095 in. Their interpretation in expansions as well is useful for unquoted strings,
8096 and for other cases such as looked-up strings that are then expanded.
8099 .section "Testing string expansions"
8100 .cindex "expansion" "testing"
8101 .cindex "testing" "string expansion"
8102 .cindex "&%-be%& option"
8103 Many expansions can be tested by calling Exim with the &%-be%& option. This
8104 takes the command arguments, or lines from the standard input if there are no
8105 arguments, runs them through the string expansion code, and writes the results
8106 to the standard output. Variables based on configuration values are set up, but
8107 since no message is being processed, variables such as &$local_part$& have no
8108 value. Nevertheless the &%-be%& option can be useful for checking out file and
8109 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8112 Exim gives up its root privilege when it is called with the &%-be%& option, and
8113 instead runs under the uid and gid it was called with, to prevent users from
8114 using &%-be%& for reading files to which they do not have access.
8118 .section "Forced expansion failure" "SECTforexpfai"
8119 .cindex "expansion" "forced failure"
8120 A number of expansions that are described in the following section have
8121 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8122 (which are sometimes called &"curly brackets"&). Which of the two strings is
8123 used depends on some condition that is evaluated as part of the expansion. If,
8124 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8125 the entire string expansion fails in a way that can be detected by the code
8126 that requested the expansion. This is called &"forced expansion failure"&, and
8127 its consequences depend on the circumstances. In some cases it is no different
8128 from any other expansion failure, but in others a different action may be
8129 taken. Such variations are mentioned in the documentation of the option that is
8135 .section "Expansion items" "SECTexpansionitems"
8136 The following items are recognized in expanded strings. White space may be used
8137 between sub-items that are keywords or substrings enclosed in braces inside an
8138 outer set of braces, to improve readability. &*Warning*&: Within braces,
8139 white space is significant.
8142 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8143 .cindex "expansion" "variables"
8144 Substitute the contents of the named variable, for example:
8149 The second form can be used to separate the name from subsequent alphanumeric
8150 characters. This form (using braces) is available only for variables; it does
8151 &'not'& apply to message headers. The names of the variables are given in
8152 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8153 given, the expansion fails.
8155 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8156 .cindex "expansion" "operators"
8157 The string is first itself expanded, and then the operation specified by
8158 <&'op'&> is applied to it. For example:
8162 The string starts with the first character after the colon, which may be
8163 leading white space. A list of operators is given in section &<<SECTexpop>>&
8164 below. The operator notation is used for simple expansion items that have just
8165 one argument, because it reduces the number of braces and therefore makes the
8166 string easier to understand.
8168 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8169 {*&<&'arg'&>&*}...}*&"
8171 This expansion dynamically loads and then calls a locally-written C function.
8172 This functionality is available only if Exim is compiled with
8176 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8177 object so that it doesn't reload the same object file in the same Exim process
8178 (but of course Exim does start new processes frequently).
8180 There may be from zero to eight arguments to the function. When compiling
8181 a local function that is to be called in this way, &_local_scan.h_& should be
8182 included. The Exim variables and functions that are defined by that API
8183 are also available for dynamically loaded functions. The function itself
8184 must have the following type:
8186 int dlfunction(uschar **yield, int argc, uschar *argv[])
8188 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8189 function should return one of the following values:
8191 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8192 into the expanded string that is being built.
8194 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8195 from &'yield'&, if it is set.
8197 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8198 taken from &'yield'& if it is set.
8200 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8202 When compiling a function that is to be used in this way with gcc,
8203 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8204 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8206 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8207 {*&<&'string3'&>&*}}*&"
8208 .cindex "expansion" "extracting substrings by key"
8209 .cindex "&%extract%&" "substrings by key"
8210 The key and <&'string1'&> are first expanded separately. Leading and trailing
8211 white space is removed from the key (but not from any of the strings). The key
8212 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8215 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8218 where the equals signs and spaces (but not both) are optional. If any of the
8219 values contain white space, they must be enclosed in double quotes, and any
8220 values that are enclosed in double quotes are subject to escape processing as
8221 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8222 for the value that corresponds to the key. The search is case-insensitive. If
8223 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8224 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8225 variable &$value$& contains the value that has been extracted. Afterwards, it
8226 is restored to any previous value it might have had.
8228 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8229 key is not found. If {<&'string2'&>} is also omitted, the value that was
8230 extracted is used. Thus, for example, these two expansions are identical, and
8233 ${extract{gid}{uid=1984 gid=2001}}
8234 ${extract{gid}{uid=1984 gid=2001}{$value}}
8236 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8237 appear, for example:
8239 ${extract{Z}{A=... B=...}{$value} fail }
8241 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8242 {<&'string2'&>} must be present for &"fail"& to be recognized.
8245 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8246 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8247 .cindex "expansion" "extracting substrings by number"
8248 .cindex "&%extract%&" "substrings by number"
8249 The <&'number'&> argument must consist entirely of decimal digits,
8250 apart from leading and trailing white space, which is ignored.
8251 This is what distinguishes this form of &%extract%& from the previous kind. It
8252 behaves in the same way, except that, instead of extracting a named field, it
8253 extracts from <&'string1'&> the field whose number is given as the first
8254 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8255 <&'string3'&> as before.
8257 The fields in the string are separated by any one of the characters in the
8258 separator string. These may include space or tab characters.
8259 The first field is numbered one. If the number is negative, the fields are
8260 counted from the end of the string, with the rightmost one numbered -1. If the
8261 number given is zero, the entire string is returned. If the modulus of the
8262 number is greater than the number of fields in the string, the result is the
8263 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8264 provided. For example:
8266 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8270 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8272 yields &"99"&. Two successive separators mean that the field between them is
8273 empty (for example, the fifth field above).
8276 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8277 .cindex "hash function" "textual"
8278 .cindex "expansion" "textual hash"
8279 This is a textual hashing function, and was the first to be implemented in
8280 early versions of Exim. In current releases, there are other hashing functions
8281 (numeric, MD5, and SHA-1), which are described below.
8283 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
8284 <&'n'&>. If you are using fixed values for these numbers, that is, if
8285 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
8286 use the simpler operator notation that avoids some of the braces:
8288 ${hash_<n>_<m>:<string>}
8290 The second number is optional (in both notations). If <&'n'&> is greater than
8291 or equal to the length of the string, the expansion item returns the string.
8292 Otherwise it computes a new string of length <&'n'&> by applying a hashing
8293 function to the string. The new string consists of characters taken from the
8294 first <&'m'&> characters of the string
8296 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8298 If <&'m'&> is not present the value 26 is used, so that only lower case
8299 letters appear. For example:
8301 &`$hash{3}{monty}} `& yields &`jmg`&
8302 &`$hash{5}{monty}} `& yields &`monty`&
8303 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
8306 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
8307 &*$h_*&<&'header&~name'&>&*:*&"
8308 See &*$rheader*& below.
8310 .vitem "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8311 &*$bh_*&<&'header&~name'&>&*:*&"
8312 See &*$rheader*& below.
8314 .vitem "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8315 &*$rh_*&<&'header&~name'&>&*:*&"
8316 .cindex "expansion" "header insertion"
8317 .cindex "&$header_$&"
8318 .cindex "&$bheader_$&"
8319 .cindex "&$rheader_$&"
8320 .cindex "header lines" "in expansion strings"
8321 .cindex "header lines" "character sets"
8322 .cindex "header lines" "decoding"
8323 Substitute the contents of the named message header line, for example
8327 The newline that terminates a header line is not included in the expansion, but
8328 internal newlines (caused by splitting the header line over several physical
8329 lines) may be present.
8331 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
8332 the data in the header line is interpreted.
8335 .cindex "white space" "in header lines"
8336 &%rheader%& gives the original &"raw"& content of the header line, with no
8337 processing at all, and without the removal of leading and trailing white space.
8340 .cindex "base64 encoding" "in header lines"
8341 &%bheader%& removes leading and trailing white space, and then decodes base64
8342 or quoted-printable MIME &"words"& within the header text, but does no
8343 character set translation. If decoding of what looks superficially like a MIME
8344 &"word"& fails, the raw string is returned. If decoding
8345 .cindex "binary zero" "in header line"
8346 produces a binary zero character, it is replaced by a question mark &-- this is
8347 what Exim does for binary zeros that are actually received in header lines.
8350 &%header%& tries to translate the string as decoded by &%bheader%& to a
8351 standard character set. This is an attempt to produce the same string as would
8352 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
8353 returned. Translation is attempted only on operating systems that support the
8354 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
8355 a system Makefile or in &_Local/Makefile_&.
8358 In a filter file, the target character set for &%header%& can be specified by a
8359 command of the following form:
8361 headers charset "UTF-8"
8363 This command affects all references to &$h_$& (or &$header_$&) expansions in
8364 subsequently obeyed filter commands. In the absence of this command, the target
8365 character set in a filter is taken from the setting of the &%headers_charset%&
8366 option in the runtime configuration. The value of this option defaults to the
8367 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
8370 Header names follow the syntax of RFC 2822, which states that they may contain
8371 any printing characters except space and colon. Consequently, curly brackets
8372 &'do not'& terminate header names, and should not be used to enclose them as
8373 if they were variables. Attempting to do so causes a syntax error.
8375 Only header lines that are common to all copies of a message are visible to
8376 this mechanism. These are the original header lines that are received with the
8377 message, and any that are added by an ACL &%warn%& statement or by a system
8378 filter. Header lines that are added to a particular copy of a message by a
8379 router or transport are not accessible.
8381 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8382 before the DATA ACL, because the header structure is not set up until the
8383 message is received. Header lines that are added by &%warn%& statements in a
8384 RCPT ACL (for example) are saved until the message's incoming header lines
8385 are available, at which point they are added. When a DATA ACL is running,
8386 however, header lines added by earlier ACLs are visible.
8388 Upper case and lower case letters are synonymous in header names. If the
8389 following character is white space, the terminating colon may be omitted, but
8390 this is not recommended, because you may then forget it when it is needed. When
8391 white space terminates the header name, it is included in the expanded string.
8392 If the message does not contain the given header, the expansion item is
8393 replaced by an empty string. (See the &%def%& condition in section
8394 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
8396 If there is more than one header with the same name, they are all
8397 concatenated to form the substitution string, up to a maximum length of 64K. A
8398 newline character is inserted between each line. For the &%header%& expansion,
8399 for those headers that contain lists of addresses, a comma is also inserted at
8400 the junctions between lines. This does not happen for the &%rheader%&
8404 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
8405 .cindex "expansion" "hmac hashing"
8407 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
8408 shared secret and some text into a message authentication code, as specified in
8409 RFC 2104. This differs from &`${md5:secret_text...}`& or
8410 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
8411 cryptographic hash, allowing for authentication that is not possible with MD5
8412 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
8413 present. For example:
8415 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
8417 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
8420 dd97e3ba5d1a61b5006108f8c8252953
8422 As an example of how this might be used, you might put in the main part of
8423 an Exim configuration:
8425 SPAMSCAN_SECRET=cohgheeLei2thahw
8427 In a router or a transport you could then have:
8430 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
8431 ${hmac{md5}{SPAMSCAN_SECRET}\
8432 {${primary_hostname},${message_exim_id},$h_message-id:}}
8434 Then given a message, you can check where it was scanned by looking at the
8435 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
8436 this header line is authentic by recomputing the authentication code from the
8437 host name, message ID and the &'Message-id:'& header line. This can be done
8438 using Exim's &%-be%& option, or by other means, for example by using the
8439 &'hmac_md5_hex()'& function in Perl.
8442 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8443 .cindex "expansion" "conditional"
8444 .cindex "&%if%&, expansion item"
8445 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
8446 item; otherwise <&'string2'&> is used. The available conditions are described
8447 in section &<<SECTexpcond>>& below. For example:
8449 ${if eq {$local_part}{postmaster} {yes}{no} }
8451 The second string need not be present; if it is not and the condition is not
8452 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
8453 be present instead of the second string (without any curly brackets). In this
8454 case, the expansion is forced to fail if the condition is not true (see section
8455 &<<SECTforexpfai>>&).
8457 If both strings are omitted, the result is the string &`true`& if the condition
8458 is true, and the empty string if the condition is false. This makes it less
8459 cumbersome to write custom ACL and router conditions. For example, instead of
8461 condition = ${if >{$acl_m4}{3}{true}{false}}
8465 condition = ${if >{$acl_m4}{3}}
8468 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8469 .cindex "expansion" "string truncation"
8470 .cindex "&%length%&" "expansion item"
8471 The &%length%& item is used to extract the initial portion of a string. Both
8472 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
8473 you are using a fixed value for the number, that is, if <&'string1'&> does not
8474 change when expanded, you can use the simpler operator notation that avoids
8477 ${length_<n>:<string>}
8479 The result of this item is either the first <&'n'&> characters or the whole
8480 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
8481 &%strlen%&, which gives the length of a string.
8484 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
8485 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8486 This is the first of one of two different types of lookup item, which are both
8487 described in the next item.
8489 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
8490 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8491 .cindex "expansion" "lookup in"
8492 .cindex "file" "lookups"
8493 .cindex "lookup" "in expanded string"
8494 The two forms of lookup item specify data lookups in files and databases, as
8495 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
8496 lookups, and the second is used for query-style lookups. The <&'key'&>,
8497 <&'file'&>, and <&'query'&> strings are expanded before use.
8499 If there is any white space in a lookup item which is part of a filter command,
8500 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
8501 other place where white space is significant, the lookup item must be enclosed
8502 in double quotes. The use of data lookups in users' filter files may be locked
8503 out by the system administrator.
8506 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
8507 During its expansion, the variable &$value$& contains the data returned by the
8508 lookup. Afterwards it reverts to the value it had previously (at the outer
8509 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
8510 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
8511 string on failure. If <&'string2'&> is provided, it can itself be a nested
8512 lookup, thus providing a mechanism for looking up a default value when the
8513 original lookup fails.
8515 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
8516 data for the outer lookup while the parameters of the second lookup are
8517 expanded, and also while <&'string2'&> of the second lookup is expanded, should
8518 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
8519 appear, and in this case, if the lookup fails, the entire expansion is forced
8520 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
8521 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
8522 successful lookup, and nothing in the case of failure.
8524 For single-key lookups, the string &"partial"& is permitted to precede the
8525 search type in order to do partial matching, and * or *@ may follow a search
8526 type to request default lookups if the key does not match (see sections
8527 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
8529 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
8530 If a partial search is used, the variables &$1$& and &$2$& contain the wild
8531 and non-wild parts of the key during the expansion of the replacement text.
8532 They return to their previous values at the end of the lookup item.
8534 This example looks up the postmaster alias in the conventional alias file:
8536 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
8538 This example uses NIS+ to look up the full name of the user corresponding to
8539 the local part of an address, forcing the expansion to fail if it is not found:
8541 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8545 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8546 .cindex "expansion" "numeric hash"
8547 .cindex "hash function" "numeric"
8548 The three strings are expanded; the first two must yield numbers. Call them
8549 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
8550 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
8551 can use the simpler operator notation that avoids some of the braces:
8553 ${nhash_<n>_<m>:<string>}
8555 The second number is optional (in both notations). If there is only one number,
8556 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
8557 processed by a div/mod hash function that returns two numbers, separated by a
8558 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
8561 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8563 returns the string &"6/33"&.
8567 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
8568 .cindex "Perl" "use in expanded string"
8569 .cindex "expansion" "calling Perl from"
8570 This item is available only if Exim has been built to include an embedded Perl
8571 interpreter. The subroutine name and the arguments are first separately
8572 expanded, and then the Perl subroutine is called with those arguments. No
8573 additional arguments need be given; the maximum number permitted, including the
8574 name of the subroutine, is nine.
8576 The return value of the subroutine is inserted into the expanded string, unless
8577 the return value is &%undef%&. In that case, the expansion fails in the same
8578 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
8579 Whatever you return is evaluated in a scalar context. For example, if you
8580 return the name of a Perl vector, the return value is the size of the vector,
8583 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
8584 with the error message that was passed to &%die%&. More details of the embedded
8585 Perl facility are given in chapter &<<CHAPperl>>&.
8587 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
8588 out the use of this expansion item in filter files.
8591 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
8592 .cindex "prvs" "expansion item"
8593 The first argument is a complete email address and the second is secret
8594 keystring. The third argument, specifying a key number, is optional. If absent,
8595 it defaults to 0. The result of the expansion is a prvs-signed email address,
8596 to be typically used with the &%return_path%& option on an &(smtp)& transport
8597 as part of a bounce address tag validation (BATV) scheme. For more discussion
8598 and an example, see section &<<SECTverifyPRVS>>&.
8600 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
8601 {*&<&'string'&>&*}}*&"
8602 .cindex "prvscheck" "expansion item"
8603 This expansion item is the complement of the &%prvs%& item. It is used for
8604 checking prvs-signed addresses. If the expansion of the first argument does not
8605 yield a syntactically valid prvs-signed address, the whole item expands to the
8606 empty string. When the first argument does expand to a syntactically valid
8607 prvs-signed address, the second argument is expanded, with the prvs-decoded
8608 version of the address and the key number extracted from the address in the
8609 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
8611 These two variables can be used in the expansion of the second argument to
8612 retrieve the secret. The validity of the prvs-signed address is then checked
8613 against the secret. The result is stored in the variable &$prvscheck_result$&,
8614 which is empty for failure or &"1"& for success.
8616 The third argument is optional; if it is missing, it defaults to an empty
8617 string. This argument is now expanded. If the result is an empty string, the
8618 result of the expansion is the decoded version of the address. This is the case
8619 whether or not the signature was valid. Otherwise, the result of the expansion
8620 is the expansion of the third argument.
8622 All three variables can be used in the expansion of the third argument.
8623 However, once the expansion is complete, only &$prvscheck_result$& remains set.
8624 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
8626 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
8627 .cindex "expansion" "inserting an entire file"
8628 .cindex "file" "inserting into expansion"
8629 .cindex "&%readfile%& expansion item"
8630 The file name and end-of-line string are first expanded separately. The file is
8631 then read, and its contents replace the entire item. All newline characters in
8632 the file are replaced by the end-of-line string if it is present. Otherwise,
8633 newlines are left in the string.
8634 String expansion is not applied to the contents of the file. If you want this,
8635 you must wrap the item in an &%expand%& operator. If the file cannot be read,
8636 the string expansion fails.
8638 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
8639 locks out the use of this expansion item in filter files.
8643 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
8644 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
8645 .cindex "expansion" "inserting from a socket"
8646 .cindex "socket" "use of in expansion"
8647 .cindex "&%readsocket%& expansion item"
8648 This item inserts data that is read from a Unix domain socket into the expanded
8649 string. The minimal way of using it uses just two arguments:
8651 ${readsocket{/socket/name}{request string}}
8653 Exim connects to the socket, writes the request string (unless it is an
8654 empty string) and reads from the socket until an end-of-file is read. A timeout
8655 of 5 seconds is applied. Additional, optional arguments extend what can be
8656 done. Firstly, you can vary the timeout. For example:
8658 ${readsocket{/socket/name}{request-string}{3s}}
8660 A fourth argument allows you to change any newlines that are in the data
8661 that is read, in the same way as for &%readfile%& (see above). This example
8662 turns them into spaces:
8664 ${readsocket{/socket/name}{request-string}{3s}{ }}
8666 As with all expansions, the substrings are expanded before the processing
8667 happens. Errors in these sub-expansions cause the expansion to fail. In
8668 addition, the following errors can occur:
8671 Failure to create a socket file descriptor;
8673 Failure to connect the socket;
8675 Failure to write the request-string;
8677 Timeout on reading from the socket.
8680 By default, any of these errors causes the expansion to fail. However, if
8681 you supply a fifth substring, it is expanded and used when any of the above
8682 errors occurs. For example:
8684 ${readsocket{/socket/name}{request-string}{3s}{\n}\
8687 You can test for the existence of the socket by wrapping this expansion in
8688 &`${if exists`&, but there is a race condition between that test and the
8689 actual opening of the socket, so it is safer to use the fifth argument if you
8690 want to be absolutely sure of avoiding an expansion error for a non-existent
8693 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
8694 locks out the use of this expansion item in filter files.
8696 .vitem &*$rheader_*&<&'header&~name'&>&*:&~or&~$rh_*&<&'header&~name'&>&*:*&
8697 This item inserts &"raw"& header lines. It is described with the &%header%&
8698 expansion item above.
8700 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
8701 {*&<&'string2'&>&*}}*&"
8702 .cindex "expansion" "running a command"
8703 .cindex "&%run%& expansion item"
8704 The command and its arguments are first expanded separately, and then the
8705 command is run in a separate process, but under the same uid and gid. As in
8706 other command executions from Exim, a shell is not used by default. If you want
8707 a shell, you must explicitly code it.
8709 .cindex "return code" "from &%run%& expansion"
8711 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
8712 and replaces the entire item; during this expansion, the standard output from
8713 the command is in the variable &$value$&. If the command fails, <&'string2'&>,
8714 if present, is expanded and used. Once again, during the expansion, the
8715 standard output from the command is in the variable &$value$&. If <&'string2'&>
8716 is absent, the result is empty. Alternatively, <&'string2'&> can be the word
8717 &"fail"& (not in braces) to force expansion failure if the command does not
8718 succeed. If both strings are omitted, the result is contents of the standard
8719 output on success, and nothing on failure.
8722 The return code from the command is put in the variable &$runrc$&, and this
8723 remains set afterwards, so in a filter file you can do things like this:
8725 if "${run{x y z}{}}$runrc" is 1 then ...
8726 elif $runrc is 2 then ...
8730 If execution of the command fails (for example, the command does not exist),
8731 the return code is 127 &-- the same code that shells use for non-existent
8734 &*Warning*&: In a router or transport, you cannot assume the order in which
8735 option values are expanded, except for those preconditions whose order of
8736 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
8737 by the expansion of one option, and use it in another.
8739 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
8740 out the use of this expansion item in filter files.
8743 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
8744 .cindex "expansion" "string substitution"
8745 .cindex "&%sg%& expansion item"
8746 This item works like Perl's substitution operator (s) with the global (/g)
8747 option; hence its name. However, unlike the Perl equivalent, Exim does not
8748 modify the subject string; instead it returns the modified string for insertion
8749 into the overall expansion. The item takes three arguments: the subject string,
8750 a regular expression, and a substitution string. For example:
8752 ${sg{abcdefabcdef}{abc}{xyz}}
8754 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
8755 if any $ or \ characters are required in the regular expression or in the
8756 substitution string, they have to be escaped. For example:
8758 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
8760 yields &"defabc"&, and
8762 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
8764 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
8765 the regular expression from string expansion.
8769 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8770 .cindex "&%substr%&"
8771 .cindex "substring extraction"
8772 .cindex "expansion" "substring extraction"
8773 The three strings are expanded; the first two must yield numbers. Call them
8774 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
8775 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
8776 can use the simpler operator notation that avoids some of the braces:
8778 ${substr_<n>_<m>:<string>}
8780 The second number is optional (in both notations).
8781 If it is absent in the simpler format, the preceding underscore must also be
8784 The &%substr%& item can be used to extract more general substrings than
8785 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
8786 length required. For example
8788 ${substr{3}{2}{$local_part}}
8790 If the starting offset is greater than the string length the result is the
8791 null string; if the length plus starting offset is greater than the string
8792 length, the result is the right-hand part of the string, starting from the
8793 given offset. The first character in the string has offset zero.
8795 The &%substr%& expansion item can take negative offset values to count
8796 from the right-hand end of its operand. The last character is offset -1, the
8797 second-last is offset -2, and so on. Thus, for example,
8799 ${substr{-5}{2}{1234567}}
8801 yields &"34"&. If the absolute value of a negative offset is greater than the
8802 length of the string, the substring starts at the beginning of the string, and
8803 the length is reduced by the amount of overshoot. Thus, for example,
8805 ${substr{-5}{2}{12}}
8807 yields an empty string, but
8809 ${substr{-3}{2}{12}}
8813 When the second number is omitted from &%substr%&, the remainder of the string
8814 is taken if the offset is positive. If it is negative, all characters in the
8815 string preceding the offset point are taken. For example, an offset of -1 and
8816 no length, as in these semantically identical examples:
8819 ${substr{-1}{abcde}}
8821 yields all but the last character of the string, that is, &"abcd"&.
8825 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
8826 {*&<&'replacements'&>&*}}*&"
8827 .cindex "expansion" "character translation"
8828 .cindex "&%tr%& expansion item"
8829 This item does single-character translation on its subject string. The second
8830 argument is a list of characters to be translated in the subject string. Each
8831 matching character is replaced by the corresponding character from the
8832 replacement list. For example
8834 ${tr{abcdea}{ac}{13}}
8836 yields &`1b3de1`&. If there are duplicates in the second character string, the
8837 last occurrence is used. If the third string is shorter than the second, its
8838 last character is replicated. However, if it is empty, no translation takes
8844 .section "Expansion operators" "SECTexpop"
8845 .cindex "expansion" "operators"
8846 For expansion items that perform transformations on a single argument string,
8847 the &"operator"& notation is used because it is simpler and uses fewer braces.
8848 The substring is first expanded before the operation is applied to it. The
8849 following operations can be performed:
8852 .vitem &*${address:*&<&'string'&>&*}*&
8853 .cindex "expansion" "RFC 2822 address handling"
8854 .cindex "&%address%&" "expansion item"
8855 The string is interpreted as an RFC 2822 address, as it might appear in a
8856 header line, and the effective address is extracted from it. If the string does
8857 not parse successfully, the result is empty.
8860 .vitem &*${base62:*&<&'digits'&>&*}*&
8861 .cindex "&%base62%&"
8862 .cindex "expansion" "conversion to base 62"
8863 The string must consist entirely of decimal digits. The number is converted to
8864 base 62 and output as a string of six characters, including leading zeros. In
8865 the few operating environments where Exim uses base 36 instead of base 62 for
8866 its message identifiers (because those systems do not have case-sensitive file
8867 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
8868 be absolutely clear: this is &'not'& base64 encoding.
8870 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
8871 .cindex "&%base62d%&"
8872 .cindex "expansion" "conversion to base 62"
8873 The string must consist entirely of base-62 digits, or, in operating
8874 environments where Exim uses base 36 instead of base 62 for its message
8875 identifiers, base-36 digits. The number is converted to decimal and output as a
8878 .vitem &*${domain:*&<&'string'&>&*}*&
8879 .cindex "domain" "extraction"
8880 .cindex "expansion" "domain extraction"
8881 The string is interpreted as an RFC 2822 address and the domain is extracted
8882 from it. If the string does not parse successfully, the result is empty.
8885 .vitem &*${escape:*&<&'string'&>&*}*&
8886 .cindex "expansion" "escaping non-printing characters"
8887 .cindex "&%escape%&, expansion item"
8888 If the string contains any non-printing characters, they are converted to
8889 escape sequences starting with a backslash. Whether characters with the most
8890 significant bit set (so-called &"8-bit characters"&) count as printing or not
8891 is controlled by the &%print_topbitchars%& option.
8894 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
8895 .cindex "expansion" "expression evaluation"
8896 .cindex "expansion" "arithmetic expression"
8897 .cindex "&%eval%& expansion item"
8898 These items supports simple arithmetic in expansion strings. The string (after
8899 expansion) must be a conventional arithmetic expression, but it is limited to
8900 five basic operators (plus, minus, times, divide, remainder) and parentheses.
8901 All operations are carried out using integer arithmetic. Plus and minus have a
8902 lower priority than times, divide, and remainder; operators with the same
8903 priority are evaluated from left to right.
8905 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
8906 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
8907 decimal, even if they start with a leading zero. This can be useful when
8908 processing numbers extracted from dates or times, which often do have leading
8911 A number may be followed by &"K"& or &"M"& to multiply it by 1024 or 1024*1024,
8912 respectively. Negative numbers are supported. The result of the computation is
8913 a decimal representation of the answer (without &"K"& or &"M"&). For example:
8916 &`${eval:1+1} `& yields 2
8917 &`${eval:1+2*3} `& yields 7
8918 &`${eval:(1+2)*3} `& yields 9
8919 &`${eval:2+42%5} `& yields 4
8922 As a more realistic example, in an ACL you might have
8924 deny message = Too many bad recipients
8927 {>{$rcpt_count}{10}} \
8930 {$recipients_count} \
8931 {${eval:$rcpt_count/2}} \
8935 The condition is true if there have been more than 10 RCPT commands and
8936 fewer than half of them have resulted in a valid recipient.
8939 .vitem &*${expand:*&<&'string'&>&*}*&
8940 .cindex "expansion" "re-expansion of substring"
8941 The &%expand%& operator causes a string to be expanded for a second time. For
8944 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
8946 first looks up a string in a file while expanding the operand for &%expand%&,
8947 and then re-expands what it has found.
8950 .vitem &*${from_utf8:*&<&'string'&>&*}*&
8952 .cindex "UTF-8" "conversion from"
8953 .cindex "expansion" "UTF-8 conversion"
8954 .cindex "&%from_utf8%&"
8955 The world is slowly moving towards Unicode, although there are no standards for
8956 email yet. However, other applications (including some databases) are starting
8957 to store data in Unicode, using UTF-8 encoding. This operator converts from a
8958 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
8959 converted to underscores. The input must be a valid UTF-8 string. If it is not,
8960 the result is an undefined sequence of bytes.
8962 Unicode code points with values less than 256 are compatible with ASCII and
8963 ISO-8859-1 (also known as Latin-1).
8964 For example, character 169 is the copyright symbol in both cases, though the
8965 way it is encoded is different. In UTF-8, more than one byte is needed for
8966 characters with code values greater than 127, whereas ISO-8859-1 is a
8967 single-byte encoding (but thereby limited to 256 characters). This makes
8968 translation from UTF-8 to ISO-8859-1 straightforward.
8971 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
8972 .cindex "hash function" "textual"
8973 .cindex "expansion" "textual hash"
8974 The &%hash%& operator is a simpler interface to the hashing function that can
8975 be used when the two parameters are fixed numbers (as opposed to strings that
8976 change when expanded). The effect is the same as
8978 ${hash{<n>}{<m>}{<string>}}
8980 See the description of the general &%hash%& item above for details. The
8981 abbreviation &%h%& can be used when &%hash%& is used as an operator.
8985 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
8986 .cindex "base64 encoding" "conversion from hex"
8987 .cindex "expansion" "hex to base64"
8988 .cindex "&%hex2b64%&"
8989 This operator converts a hex string into one that is base64 encoded. This can
8990 be useful for processing the output of the MD5 and SHA-1 hashing functions.
8993 .vitem &*${lc:*&<&'string'&>&*}*&
8994 .cindex "case forcing in strings"
8995 .cindex "string" "case forcing"
8996 .cindex "lower casing"
8997 .cindex "expansion" "case forcing"
8998 .cindex "&%lc%& expansion item"
8999 This forces the letters in the string into lower-case, for example:
9004 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9005 .cindex "expansion" "string truncation"
9006 .cindex "&%length%&" "expansion item"
9007 The &%length%& operator is a simpler interface to the &%length%& function that
9008 can be used when the parameter is a fixed number (as opposed to a string that
9009 changes when expanded). The effect is the same as
9011 ${length{<number>}{<string>}}
9013 See the description of the general &%length%& item above for details. Note that
9014 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9015 when &%length%& is used as an operator.
9018 .vitem &*${local_part:*&<&'string'&>&*}*&
9019 .cindex "expansion" "local part extraction"
9020 .cindex "&%local_part%& expansion item"
9021 The string is interpreted as an RFC 2822 address and the local part is
9022 extracted from it. If the string does not parse successfully, the result is
9026 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9027 .cindex "masked IP address"
9028 .cindex "IP address" "masking"
9029 .cindex "CIDR notation"
9030 .cindex "expansion" "IP address masking"
9031 .cindex "&%mask%&, expansion item"
9032 If the form of the string to be operated on is not an IP address followed by a
9033 slash and an integer (that is, a network address in CIDR notation), the
9034 expansion fails. Otherwise, this operator converts the IP address to binary,
9035 masks off the least significant bits according to the bit count, and converts
9036 the result back to text, with mask appended. For example,
9038 ${mask:10.111.131.206/28}
9040 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9041 be mostly used for looking up masked addresses in files, the result for an IPv6
9042 address uses dots to separate components instead of colons, because colon
9043 terminates a key string in lsearch files. So, for example,
9045 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9049 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9051 Letters in IPv6 addresses are always output in lower case.
9054 .vitem &*${md5:*&<&'string'&>&*}*&
9056 .cindex "expansion" "MD5 hash"
9057 .cindex "&%md5%& expansion item"
9058 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9059 as a 32-digit hexadecimal number, in which any letters are in lower case.
9062 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9063 .cindex "expansion" "numeric hash"
9064 .cindex "hash function" "numeric"
9065 The &%nhash%& operator is a simpler interface to the numeric hashing function
9066 that can be used when the two parameters are fixed numbers (as opposed to
9067 strings that change when expanded). The effect is the same as
9069 ${nhash{<n>}{<m>}{<string>}}
9071 See the description of the general &%nhash%& item above for details.
9074 .vitem &*${quote:*&<&'string'&>&*}*&
9075 .cindex "quoting" "in string expansions"
9076 .cindex "expansion" "quoting"
9077 .cindex "&%quote%&, expansion item"
9078 The &%quote%& operator puts its argument into double quotes if it
9079 is an empty string or
9080 contains anything other than letters, digits, underscores, dots, and hyphens.
9081 Any occurrences of double quotes and backslashes are escaped with a backslash.
9082 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
9083 respectively For example,
9091 The place where this is useful is when the argument is a substitution from a
9092 variable or a message header.
9094 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
9095 .cindex "&%quote_local_part%& expansion item"
9096 This operator is like &%quote%&, except that it quotes the string only if
9097 required to do so by the rules of RFC 2822 for quoting local parts. For
9098 example, a plus sign would not cause quoting (but it would for &%quote%&).
9099 If you are creating a new email address from the contents of &$local_part$&
9100 (or any other unknown data), you should always use this operator.
9103 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
9104 .cindex "quoting" "lookup-specific"
9105 This operator applies lookup-specific quoting rules to the string. Each
9106 query-style lookup type has its own quoting rules which are described with
9107 the lookups in chapter &<<CHAPfdlookup>>&. For example,
9109 ${quote_ldap:two * two}
9115 For single-key lookup types, no quoting is ever necessary and this operator
9116 yields an unchanged string.
9119 .vitem &*${rxquote:*&<&'string'&>&*}*&
9120 .cindex "quoting" "in regular expressions"
9121 .cindex "regular expressions" "quoting"
9122 .cindex "&%rxquote%& expansion item"
9123 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
9124 characters in its argument. This is useful when substituting the values of
9125 variables or headers inside regular expressions.
9128 .vitem &*${rfc2047:*&<&'string'&>&*}*&
9129 .cindex "expansion" "RFC 2047"
9130 .cindex "RFC 2047" "expansion operator"
9131 .cindex "&%rfc2047%& expansion item"
9132 This operator encodes text according to the rules of RFC 2047. This is an
9133 encoding that is used in header lines to encode non-ASCII characters. It is
9134 assumed that the input string is in the encoding specified by the
9135 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
9136 contains only characters in the range 33&--126, and no instances of the
9139 ? = ( ) < > @ , ; : \ " . [ ] _
9141 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
9142 string, using as many &"encoded words"& as necessary to encode all the
9147 .vitem &*${sha1:*&<&'string'&>&*}*&
9148 .cindex "SHA-1 hash"
9149 .cindex "expansion" "SHA-1 hashing"
9150 .cindex "&%sha2%& expansion item"
9151 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
9152 it as a 40-digit hexadecimal number, in which any letters are in upper case.
9155 .vitem &*${stat:*&<&'string'&>&*}*&
9156 .cindex "expansion" "statting a file"
9157 .cindex "file" "extracting characteristics"
9158 .cindex "&%stat%& expansion item"
9159 The string, after expansion, must be a file path. A call to the &[stat()]&
9160 function is made for this path. If &[stat()]& fails, an error occurs and the
9161 expansion fails. If it succeeds, the data from the stat replaces the item, as a
9162 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
9163 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
9164 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
9165 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
9166 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
9167 can extract individual fields using the &%extract%& expansion item.
9169 The use of the &%stat%& expansion in users' filter files can be locked out by
9170 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
9171 systems for files larger than 2GB.
9173 .vitem &*${str2b64:*&<&'string'&>&*}*&
9174 .cindex "expansion" "base64 encoding"
9175 .cindex "base64 encoding" "in string expansion"
9176 .cindex "&%str2b64%& expansion item"
9177 This operator converts a string into one that is base64 encoded.
9181 .vitem &*${strlen:*&<&'string'&>&*}*&
9182 .cindex "expansion" "string length"
9183 .cindex "string" "length in expansion"
9184 .cindex "&%strlen%& expansion item"
9185 The item is replace by the length of the expanded string, expressed as a
9186 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
9189 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
9190 .cindex "&%substr%& expansion item"
9191 .cindex "substring extraction"
9192 .cindex "expansion" "substring expansion"
9193 The &%substr%& operator is a simpler interface to the &%substr%& function that
9194 can be used when the two parameters are fixed numbers (as opposed to strings
9195 that change when expanded). The effect is the same as
9197 ${substr{<start>}{<length>}{<string>}}
9199 See the description of the general &%substr%& item above for details. The
9200 abbreviation &%s%& can be used when &%substr%& is used as an operator.
9203 .vitem &*${time_eval:*&<&'string'&>&*}*&
9204 .cindex "&%time_eval%& expansion item"
9205 .cindex "time interval" "decoding"
9206 This item converts an Exim time interval such as &`2d4h5m`& into a number of
9210 .vitem &*${time_interval:*&<&'string'&>&*}*&
9211 .cindex "&%time_interval%& expansion item"
9212 .cindex "time interval" "formatting"
9213 The argument (after sub-expansion) must be a sequence of decimal digits that
9214 represents an interval of time as a number of seconds. It is converted into a
9215 number of larger units and output in Exim's normal time format, for example,
9218 .vitem &*${uc:*&<&'string'&>&*}*&
9219 .cindex "case forcing in strings"
9220 .cindex "string" "case forcing"
9221 .cindex "upper casing"
9222 .cindex "expansion" "case forcing"
9223 .cindex "&%uc%& expansion item"
9224 This forces the letters in the string into upper-case.
9232 .section "Expansion conditions" "SECTexpcond"
9233 .cindex "expansion" "conditions"
9234 The following conditions are available for testing by the &%${if%& construct
9235 while expanding strings:
9238 .vitem &*!*&<&'condition'&>
9239 .cindex "expansion" "negating a condition"
9240 .cindex "negation" "in expansion condition"
9241 Preceding any condition with an exclamation mark negates the result of the
9244 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9245 .cindex "numeric comparison"
9246 .cindex "expansion" "numeric comparison"
9247 There are a number of symbolic operators for doing numeric comparisons. They
9253 &`>= `& greater or equal
9255 &`<= `& less or equal
9259 ${if >{$message_size}{10M} ...
9261 Note that the general negation operator provides for inequality testing. The
9262 two strings must take the form of optionally signed decimal integers,
9263 optionally followed by one of the letters &"K"& or &"M"& (in either upper or
9264 lower case), signifying multiplication by 1024 or 1024*1024, respectively.
9266 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9267 .cindex "expansion" "encrypted comparison"
9268 .cindex "encrypted strings" "comparing"
9269 .cindex "&%crypteq%& expansion condition"
9270 This condition is included in the Exim binary if it is built to support any
9271 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
9272 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
9273 included in the binary.
9275 The &%crypteq%& condition has two arguments. The first is encrypted and
9276 compared against the second, which is already encrypted. The second string may
9277 be in the LDAP form for storing encrypted strings, which starts with the
9278 encryption type in curly brackets, followed by the data. If the second string
9279 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
9280 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
9281 Typically this will be a field from a password file. An example of an encrypted
9282 string in LDAP form is:
9284 {md5}CY9rzUYh03PK3k6DJie09g==
9286 If such a string appears directly in an expansion, the curly brackets have to
9287 be quoted, because they are part of the expansion syntax. For example:
9289 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
9291 The following encryption types (whose names are matched case-independently) are
9296 .cindex "base64 encoding" "in encrypted password"
9297 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
9298 printable characters to compare with the remainder of the second string. If the
9299 length of the comparison string is 24, Exim assumes that it is base64 encoded
9300 (as in the above example). If the length is 32, Exim assumes that it is a
9301 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
9305 .cindex "SHA-1 hash"
9306 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
9307 printable characters to compare with the remainder of the second string. If the
9308 length of the comparison string is 28, Exim assumes that it is base64 encoded.
9309 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
9310 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
9313 .cindex "&[crypt()]&"
9314 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
9315 only the first eight characters of the password. However, in modern operating
9316 systems this is no longer true, and in many cases the entire password is used,
9317 whatever its length.
9319 .cindex "&[crypt16()]&"
9320 &%{crypt16}%& calls the &[crypt16()]& function (also known as &[bigcrypt()]&),
9321 which was orginally created to use up to 16 characters of the password. Again,
9322 in modern operating systems, more characters may be used.
9325 Exim has its own version of &[crypt16()]& (which is just a double call to
9326 &[crypt()]&). For operating systems that have their own version, setting
9327 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
9328 operating system version instead of its own. This option is set by default in
9329 the OS-dependent &_Makefile_& for those operating systems that are known to
9330 support &[crypt16()]&.
9332 If you do not put any curly bracket encryption type in a &%crypteq%&
9333 comparison, the default is either &`{crypt}`& or &`{crypt16}`&, as determined
9334 by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default default is
9335 &`{crypt}`&. Whatever the default, you can always use either function by
9336 specifying it explicitly in curly brackets.
9338 Note that if a password is no longer than 8 characters, the results of
9339 encrypting it with &[crypt()]& and &[crypt16()]& are identical. That means that
9340 &[crypt16()]& is backwards compatible, as long as nobody feeds it a password
9341 longer than 8 characters.
9343 .vitem &*def:*&<&'variable&~name'&>
9344 .cindex "expansion" "checking for empty variable"
9345 .cindex "&%def%& expansion condition"
9346 The &%def%& condition must be followed by the name of one of the expansion
9347 variables defined in section &<<SECTexpvar>>&. The condition is true if the
9348 variable does not contain the empty string. For example:
9350 ${if def:sender_ident {from $sender_ident}}
9352 Note that the variable name is given without a leading &%$%& character. If the
9353 variable does not exist, the expansion fails.
9355 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
9356 &~&*def:h_*&<&'header&~name'&>&*:*&"
9357 .cindex "expansion" "checking header line existence"
9358 This condition is true if a message is being processed and the named header
9359 exists in the message. For example,
9361 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
9363 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
9364 the header name must be terminated by a colon if white space does not follow.
9366 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9367 .cindex "string" "comparison"
9368 .cindex "expansion" "string comparison"
9369 .cindex "&%eq%& expansion condition"
9370 The two substrings are first expanded. The condition is true if the two
9371 resulting strings are identical, including the case of letters.
9373 .vitem &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9374 .cindex "string" "comparison"
9375 .cindex "expansion" "string comparison"
9376 .cindex "&%eqi%& expansion condition"
9377 The two substrings are first expanded. The condition is true if the two
9378 resulting strings are identical when compared in a case-independent way.
9380 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
9381 .cindex "expansion" "file existence test"
9382 .cindex "file" "existence test"
9383 .cindex "&%exists%&, expansion condition"
9384 The substring is first expanded and then interpreted as an absolute path. The
9385 condition is true if the named file (or directory) exists. The existence test
9386 is done by calling the &[stat()]& function. The use of the &%exists%& test in
9387 users' filter files may be locked out by the system administrator.
9389 .vitem &*first_delivery*&
9390 .cindex "delivery" "first"
9391 .cindex "first delivery"
9392 .cindex "expansion" "first delivery test"
9393 .cindex "&%first_delivery%& expansion condition"
9394 This condition, which has no data, is true during a message's first delivery
9395 attempt. It is false during any subsequent delivery attempts.
9397 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9398 .cindex "&%ge%& expansion condition"
9401 .vitem &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9402 .cindex "string" "comparison"
9403 .cindex "expansion" "string comparison"
9404 .cindex "&%gei%& expansion condition"
9405 The two substrings are first expanded. The condition is true if the first
9406 string is lexically greater than or equal to the second string: for &%ge%& the
9407 comparison includes the case of letters, whereas for &%gei%& the comparison is
9410 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9411 .cindex "&%gt%& expansion condition"
9414 .vitem &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9415 .cindex "string" "comparison"
9416 .cindex "expansion" "string comparison"
9417 .cindex "&%gti%& expansion condition"
9418 The two substrings are first expanded. The condition is true if the first
9419 string is lexically greater than the second string: for &%gt%& the comparison
9420 includes the case of letters, whereas for &%gti%& the comparison is
9423 .vitem &*isip&~{*&<&'string'&>&*}*&
9424 .cindex "&%isip%& expansion condition"
9427 .vitem &*isip4&~{*&<&'string'&>&*}*&
9428 .cindex "&%isip4%& expansion condition"
9431 .vitem &*isip6&~{*&<&'string'&>&*}*&
9432 .cindex "IP address" "testing string format"
9433 .cindex "string" "testing for IP address"
9434 .cindex "&%isip6%& expansion condition"
9435 The substring is first expanded, and then tested to see if it has the form of
9436 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
9437 &%isip4%& and &%isip6%& test just for IPv4 or IPv6 addresses, respectively. For
9438 example, you could use
9440 ${if isip4{$sender_host_address}...
9442 to test which version of IP an incoming SMTP connection is using.
9445 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
9446 .cindex "LDAP" "use for authentication"
9447 .cindex "expansion" "LDAP authentication test"
9448 .cindex "&%ldapauth%& expansion condition"
9449 This condition supports user authentication using LDAP. See section
9450 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
9451 queries. For this use, the query must contain a user name and password. The
9452 query itself is not used, and can be empty. The condition is true if the
9453 password is not empty, and the user name and password are accepted by the LDAP
9454 server. An empty password is rejected without calling LDAP because LDAP binds
9455 with an empty password are considered anonymous regardless of the username, and
9456 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
9457 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
9461 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9462 .cindex "&%le%& expansion condition"
9465 .vitem &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9466 .cindex "string" "comparison"
9467 .cindex "expansion" "string comparison"
9468 .cindex "&%lei%& expansion condition"
9469 The two substrings are first expanded. The condition is true if the first
9470 string is lexically less than or equal to the second string: for &%le%& the
9471 comparison includes the case of letters, whereas for &%lei%& the comparison is
9474 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9475 .cindex "&%lt%& expansion condition"
9478 .vitem &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9479 .cindex "string" "comparison"
9480 .cindex "expansion" "string comparison"
9481 .cindex "&%lti%& expansion condition"
9482 The two substrings are first expanded. The condition is true if the first
9483 string is lexically less than the second string: for &%lt%& the comparison
9484 includes the case of letters, whereas for &%lti%& the comparison is
9488 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9489 .cindex "expansion" "regular expression comparison"
9490 .cindex "regular expressions" "match in expanded string"
9491 .cindex "&%match%&, expansion condition"
9492 The two substrings are first expanded. The second is then treated as a regular
9493 expression and applied to the first. Because of the pre-expansion, if the
9494 regular expression contains dollar, or backslash characters, they must be
9495 escaped. Care must also be taken if the regular expression contains braces
9496 (curly brackets). A closing brace must be escaped so that it is not taken as a
9497 premature termination of <&'string2'&>. The easiest approach is to use the
9498 &`\N`& feature to disable expansion of the regular expression.
9501 ${if match {$local_part}{\N^\d{3}\N} ...
9503 If the whole expansion string is in double quotes, further escaping of
9504 backslashes is also required.
9506 The condition is true if the regular expression match succeeds.
9507 The regular expression is not required to begin with a circumflex
9508 metacharacter, but if there is no circumflex, the expression is not anchored,
9509 and it may match anywhere in the subject, not just at the start. If you want
9510 the pattern to match at the end of the subject, you must include the &`$`&
9511 metacharacter at an appropriate point.
9513 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
9514 At the start of an &%if%& expansion the values of the numeric variable
9515 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
9516 succeeds causes them to be reset to the substrings of that condition and they
9517 will have these values during the expansion of the success string. At the end
9518 of the &%if%& expansion, the previous values are restored. After testing a
9519 combination of conditions using &%or%&, the subsequent values of the numeric
9520 variables are those of the condition that succeeded.
9522 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9523 .cindex "&%match_address%& expansion condition"
9524 See &*match_local_part*&.
9526 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9527 .cindex "&%match_domain%& expansion condition"
9528 See &*match_local_part*&.
9530 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9531 .cindex "&%match_ip%& expansion condition"
9532 This condition matches an IP address to a list of IP address patterns. It must
9533 be followed by two argument strings. The first (after expansion) must be an IP
9534 address or an empty string. The second (after expansion) is a restricted host
9535 list that can match only an IP address, not a host name. For example:
9537 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
9539 The specific types of host list item that are permitted in the list are:
9542 An IP address, optionally with a CIDR mask.
9544 A single asterisk, which matches any IP address.
9546 An empty item, which matches only if the IP address is empty. This could be
9547 useful for testing for a locally submitted message or one from specific hosts
9548 in a single test such as
9549 . ==== As this is a nested list, any displays it contains must be indented
9550 . ==== as otherwise they are too far to the left.
9552 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
9554 where the first item in the list is the empty string.
9556 The item @[] matches any of the local host's interface addresses.
9558 Lookups are assumed to be &"net-"& style lookups, even if &`net-`& is not
9559 specified. Thus, the following are equivalent:
9561 ${if match_ip{$sender_host_address}{lsearch;/some/file}...
9562 ${if match_ip{$sender_host_address}{net-lsearch;/some/file}...
9564 You do need to specify the &`net-`& prefix if you want to specify a
9565 specific address mask, for example, by using &`net24-`&.
9568 Consult section &<<SECThoslispatip>>& for further details of these patterns.
9570 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9571 .cindex "domain list" "in expansion condition"
9572 .cindex "address list" "in expansion condition"
9573 .cindex "local part list" "in expansion condition"
9574 .cindex "&%match_local_part%& expansion condition"
9575 This condition, together with &%match_address%& and &%match_domain%&, make it
9576 possible to test domain, address, and local part lists within expansions. Each
9577 condition requires two arguments: an item and a list to match. A trivial
9580 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
9582 In each case, the second argument may contain any of the allowable items for a
9583 list of the appropriate type. Also, because the second argument (after
9584 expansion) is a standard form of list, it is possible to refer to a named list.
9585 Thus, you can use conditions like this:
9587 ${if match_domain{$domain}{+local_domains}{...
9589 .cindex "&`+caseful`&"
9590 For address lists, the matching starts off caselessly, but the &`+caseful`&
9591 item can be used, as in all address lists, to cause subsequent items to
9592 have their local parts matched casefully. Domains are always matched
9595 &*Note*&: Host lists are &'not'& supported in this way. This is because
9596 hosts have two identities: a name and an IP address, and it is not clear
9597 how to specify cleanly how such a test would work. However, IP addresses can be
9598 matched using &%match_ip%&.
9600 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
9601 .cindex "PAM authentication"
9602 .cindex "AUTH" "with PAM"
9603 .cindex "Solaris" "PAM support"
9604 .cindex "expansion" "PAM authentication test"
9605 .cindex "&%pam%& expansion condition"
9606 &'Pluggable Authentication Modules'&
9607 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
9608 available in the latest releases of Solaris and in some GNU/Linux
9609 distributions. The Exim support, which is intended for use in conjunction with
9610 the SMTP AUTH command, is available only if Exim is compiled with
9614 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
9615 in some releases of GNU/Linux &%-ldl%& is also needed.
9617 The argument string is first expanded, and the result must be a
9618 colon-separated list of strings. Leading and trailing white space is ignored.
9619 The PAM module is initialized with the service name &"exim"& and the user name
9620 taken from the first item in the colon-separated data string (<&'string1'&>).
9621 The remaining items in the data string are passed over in response to requests
9622 from the authentication function. In the simple case there will only be one
9623 request, for a password, so the data consists of just two strings.
9625 There can be problems if any of the strings are permitted to contain colon
9626 characters. In the usual way, these have to be doubled to avoid being taken as
9627 separators. If the data is being inserted from a variable, the &%sg%& expansion
9628 item can be used to double any existing colons. For example, the configuration
9629 of a LOGIN authenticator might contain this setting:
9631 server_condition = ${if pam{$1:${sg{$2}{:}{::}}}{yes}{no}}
9633 For a PLAIN authenticator you could use:
9635 server_condition = ${if pam{$2:${sg{$3}{:}{::}}}{yes}{no}}
9637 In some operating systems, PAM authentication can be done only from a process
9638 running as root. Since Exim is running as the Exim user when receiving
9639 messages, this means that PAM cannot be used directly in those systems.
9640 A patched version of the &'pam_unix'& module that comes with the
9641 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
9642 The patched module allows one special uid/gid combination, in addition to root,
9643 to authenticate. If you build the patched module to allow the Exim user and
9644 group, PAM can then be used from an Exim authenticator.
9647 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
9648 .cindex "&'pwcheck'& daemon"
9650 .cindex "expansion" "&'pwcheck'& authentication test"
9651 .cindex "&%pwcheck%& expansion condition"
9652 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
9653 This is one way of making it possible for passwords to be checked by a process
9654 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
9655 deprecated. Its replacement is &'saslauthd'& (see below).
9657 The pwcheck support is not included in Exim by default. You need to specify
9658 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
9659 building Exim. For example:
9661 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
9663 You do not need to install the full Cyrus software suite in order to use
9664 the pwcheck daemon. You can compile and install just the daemon alone
9665 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
9666 access to the &_/var/pwcheck_& directory.
9668 The &%pwcheck%& condition takes one argument, which must be the user name and
9669 password, separated by a colon. For example, in a LOGIN authenticator
9670 configuration, you might have this:
9672 server_condition = ${if pwcheck{$1:$2}{1}{0}}
9674 .vitem &*queue_running*&
9675 .cindex "queue runner" "detecting when delivering from"
9676 .cindex "expansion" "queue runner test"
9677 .cindex "&%queue_runnint%& expansion condition"
9678 This condition, which has no data, is true during delivery attempts that are
9679 initiated by queue runner processes, and false otherwise.
9682 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
9684 .cindex "expansion" "Radius authentication"
9685 .cindex "&%radiu%& expansion condition"
9686 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
9687 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
9688 the Radius client configuration file in order to build Exim with Radius
9691 With just that one setting, Exim expects to be linked with the &%radiusclient%&
9692 library, using the original API. If you are using release 0.4.0 or later of
9693 this library, you need to set
9695 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
9697 in &_Local/Makefile_& when building Exim. You can also link Exim with the
9698 &%libradius%& library that comes with FreeBSD. To do this, set
9700 RADIUS_LIB_TYPE=RADLIB
9702 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
9703 You may also have to supply a suitable setting in EXTRALIBS so that the
9704 Radius library can be found when Exim is linked.
9706 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
9707 Radius client library, which calls the Radius server. The condition is true if
9708 the authentication is successful. For example:
9710 server_condition = ${if radius{<arguments>}{yes}{no}}
9714 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
9715 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
9716 .cindex "&'saslauthd'& daemon"
9718 .cindex "expansion" "&'saslauthd'& authentication test"
9719 .cindex "&%saslauthd%& expansion condition"
9720 This condition supports user authentication using the Cyrus &'saslauthd'&
9721 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
9722 Using this daemon is one way of making it possible for passwords to be checked
9723 by a process that is not running as root.
9725 The saslauthd support is not included in Exim by default. You need to specify
9726 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
9727 building Exim. For example:
9729 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
9731 You do not need to install the full Cyrus software suite in order to use
9732 the saslauthd daemon. You can compile and install just the daemon alone
9733 from the Cyrus SASL library.
9735 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
9736 two are mandatory. For example:
9738 server_condition = ${if saslauthd{{$1}{$2}}{1}{0}}
9740 The service and the realm are optional (which is why the arguments are enclosed
9741 in their own set of braces). For details of the meaning of the service and
9742 realm, and how to run the daemon, consult the Cyrus documentation.
9747 .section "Combining expansion conditions"
9748 .cindex "expansion" "combining conditions"
9749 Several conditions can be tested at once by combining them using the &%and%&
9750 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
9751 conditions on their own, and precede their lists of sub-conditions. Each
9752 sub-condition must be enclosed in braces within the overall braces that contain
9753 the list. No repetition of &%if%& is used.
9757 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
9758 .cindex "&""or""& expansion condition"
9759 .cindex "expansion" "&""or""& of conditions"
9760 The sub-conditions are evaluated from left to right. The condition is true if
9761 any one of the sub-conditions is true.
9764 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
9766 When a true sub-condition is found, the following ones are parsed but not
9767 evaluated. If there are several &"match"& sub-conditions the values of the
9768 numeric variables afterwards are taken from the first one that succeeds.
9770 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
9771 .cindex "&""and""& expansion condition"
9772 .cindex "expansion" "&""and""& of conditions"
9773 The sub-conditions are evaluated from left to right. The condition is true if
9774 all of the sub-conditions are true. If there are several &"match"&
9775 sub-conditions, the values of the numeric variables afterwards are taken from
9776 the last one. When a false sub-condition is found, the following ones are
9777 parsed but not evaluated.
9783 .section "Expansion variables" "SECTexpvar"
9784 .cindex "expansion variables" "list of"
9785 This section contains an alphabetical list of all the expansion variables. Some
9786 of them are available only when Exim is compiled with specific options such as
9787 support for TLS or the content scanning extension.
9790 .vitem "&$0$&, &$1$&, etc"
9791 .cindex "numerical variables (&$1$& &$2$& etc)"
9792 When a &%match%& expansion condition succeeds, these variables contain the
9793 captured substrings identified by the regular expression during subsequent
9794 processing of the success string of the containing &%if%& expansion item. They
9795 may also be set externally by some other matching process which precedes the
9796 expansion of the string. For example, the commands available in Exim filter
9797 files include an &%if%& command with its own regular expression matching
9800 .vitem "&$acl_c0$& &-- &$acl_c19$&"
9801 Values can be placed in these variables by the &%set%& modifier in an ACL. The
9802 values persist throughout the lifetime of an SMTP connection. They can be used
9803 to pass information between ACLs and different invocations of the same ACL.
9804 When a message is received, the values of these variables are saved with the
9805 message, and can be accessed by filters, routers, and transports during
9806 subsequent delivery.
9808 .vitem "&$acl_m0$& &-- &$acl_m19$&"
9809 Values can be placed in these variables by the &%set%& modifier in an ACL. They
9810 retain their values while a message is being received, but are reset
9811 afterwards. They are also reset by MAIL, RSET, EHLO, HELO, and after starting a
9812 TLS session. When a message is received, the values of these variables are
9813 saved with the message, and can be accessed by filters, routers, and transports
9814 during subsequent delivery.
9816 .vitem &$acl_verify_message$&
9817 .cindex "&$acl_verify_message$&"
9818 After an address verification has failed, this variable contains the failure
9819 message. It retains its value for use in subsequent modifiers. The message can
9820 be preserved by coding like this:
9822 warn !verify = sender
9823 set acl_m0 = $acl_verify_message
9825 You can use &$acl_verify_message$& during the expansion of the &%message%& or
9826 &%log_message%& modifiers, to include information about the verification
9829 .vitem &$address_data$&
9830 .cindex "&$address_data$&"
9831 This variable is set by means of the &%address_data%& option in routers. The
9832 value then remains with the address while it is processed by subsequent routers
9833 and eventually a transport. If the transport is handling multiple addresses,
9834 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
9835 for more details. &*Note*&: The contents of &$address_data$& are visible in
9838 If &$address_data$& is set when the routers are called from an ACL to verify
9839 a recipient address, the final value is still in the variable for subsequent
9840 conditions and modifiers of the ACL statement. If routing the address caused it
9841 to be redirected to just one address, the child address is also routed as part
9842 of the verification, and in this case the final value of &$address_data$& is
9843 from the child's routing.
9845 If &$address_data$& is set when the routers are called from an ACL to verify a
9846 sender address, the final value is also preserved, but this time in
9847 &$sender_address_data$&, to distinguish it from data from a recipient
9850 In both cases (recipient and sender verification), the value does not persist
9851 after the end of the current ACL statement. If you want to preserve
9852 these values for longer, you can save them in ACL variables.
9854 .vitem &$address_file$&
9855 .cindex "&$address_file$&"
9856 When, as a result of aliasing, forwarding, or filtering, a message is directed
9857 to a specific file, this variable holds the name of the file when the transport
9858 is running. At other times, the variable is empty. For example, using the
9859 default configuration, if user &%r2d2%& has a &_.forward_& file containing
9863 then when the &(address_file)& transport is running, &$address_file$&
9864 contains &"/home/r2d2/savemail"&.
9866 .cindex "Sieve filter" "value of &$address_file$&"
9867 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
9868 then up to the transport configuration to generate an appropriate absolute path
9869 to the relevant file.
9871 .vitem &$address_pipe$&
9872 .cindex "&$address_pipe$&"
9873 When, as a result of aliasing or forwarding, a message is directed to a pipe,
9874 this variable holds the pipe command when the transport is running.
9877 .vitem "&$auth1$& &-- &$auth3$&"
9878 .cindex "&$auth1$&, &$auth2$&, etc"
9879 These variables are used in SMTP authenticators (see chapters
9880 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
9883 .vitem &$authenticated_id$&
9884 .cindex "authentication" "id"
9885 .cindex "&$authenticated_id$&"
9886 When a server successfully authenticates a client it may be configured to
9887 preserve some of the authentication information in the variable
9888 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
9889 user/password authenticator configuration might preserve the user name for use
9890 in the routers. Note that this is not the same information that is saved in
9891 &$sender_host_authenticated$&. When a message is submitted locally (that is,
9892 not over a TCP connection), the value of &$authenticated_id$& is the login name
9893 of the calling process.
9895 .vitem &$authenticated_sender$&
9896 .cindex "sender" "authenticated"
9897 .cindex "authentication" "sender"
9898 .cindex "AUTH" "on MAIL command"
9899 .cindex "&$authenticated_sender$&"
9900 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
9901 SMTP MAIL command if it believes the sender is sufficiently trusted, as
9902 described in section &<<SECTauthparamail>>&. Unless the data is the string
9903 &"<>"&, it is set as the authenticated sender of the message, and the value is
9904 available during delivery in the &$authenticated_sender$& variable. If the
9905 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
9907 .cindex "&$qualify_domain$&"
9908 When a message is submitted locally (that is, not over a TCP connection), the
9909 value of &$authenticated_sender$& is an address constructed from the login
9910 name of the calling process and &$qualify_domain$&.
9913 .vitem &$authentication_failed$&
9914 .cindex "authentication" "failure"
9915 .cindex "&$authentication_failed$&"
9916 This variable is set to &"1"& in an Exim server if a client issues an AUTH
9917 command that does not succeed. Otherwise it is set to &"0"&. This makes it
9918 possible to distinguish between &"did not try to authenticate"&
9919 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
9920 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
9921 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
9922 negative response to an AUTH command, including (for example) an attempt to use
9923 an undefined mechanism.
9925 .vitem &$body_linecount$&
9926 .cindex "message body" "line count"
9927 .cindex "body of message" "line count"
9928 .cindex "&$body_linecount$&"
9929 When a message is being received or delivered, this variable contains the
9930 number of lines in the message's body. See also &$message_linecount$&.
9932 .vitem &$body_zerocount$&
9933 .cindex "message body" "binary zero count"
9934 .cindex "body of message" "binary zero count"
9935 .cindex "binary zero" "in message body"
9936 .cindex "&$body_zerocount$&"
9937 When a message is being received or delivered, this variable contains the
9938 number of binary zero bytes in the message's body.
9940 .vitem &$bounce_recipient$&
9941 .cindex "&$bounce_recipient$&"
9942 This is set to the recipient address of a bounce message while Exim is creating
9943 it. It is useful if a customized bounce message text file is in use (see
9944 chapter &<<CHAPemsgcust>>&).
9946 .vitem &$bounce_return_size_limit$&
9947 .cindex "&$bounce_return_size_limit$&"
9948 This contains the value set in the &%bounce_return_size_limit%& option, rounded
9949 up to a multiple of 1000. It is useful when a customized error message text
9950 file is in use (see chapter &<<CHAPemsgcust>>&).
9952 .vitem &$caller_gid$&
9953 .cindex "gid (group id)" "caller"
9954 .cindex "&$caller_gid$&"
9955 The real group id under which the process that called Exim was running. This is
9956 not the same as the group id of the originator of a message (see
9957 &$originator_gid$&). If Exim re-execs itself, this variable in the new
9958 incarnation normally contains the Exim gid.
9960 .vitem &$caller_uid$&
9961 .cindex "uid (user id)" "caller"
9962 .cindex "&$caller_uid$&"
9963 The real user id under which the process that called Exim was running. This is
9964 not the same as the user id of the originator of a message (see
9965 &$originator_uid$&). If Exim re-execs itself, this variable in the new
9966 incarnation normally contains the Exim uid.
9968 .vitem &$compile_date$&
9969 .cindex "&$compile_date$&"
9970 The date on which the Exim binary was compiled.
9972 .vitem &$compile_number$&
9973 .cindex "&$compile_number$&"
9974 The building process for Exim keeps a count of the number
9975 of times it has been compiled. This serves to distinguish different
9976 compilations of the same version of the program.
9978 .vitem &$demime_errorlevel$&
9979 .cindex "&$demime_errorlevel$&"
9980 This variable is available when Exim is compiled with
9981 the content-scanning extension and the obsolete &%demime%& condition. For
9982 details, see section &<<SECTdemimecond>>&.
9984 .vitem &$demime_reason$&
9985 .cindex "&$demime_reason$&"
9986 This variable is available when Exim is compiled with the
9987 content-scanning extension and the obsolete &%demime%& condition. For details,
9988 see section &<<SECTdemimecond>>&.
9991 .vitem &$dnslist_domain$&
9992 .cindex "black list (DNS)"
9993 .cindex "&$dnslist_domain$&"
9994 When a client host is found to be on a DNS (black) list,
9995 the list's domain name is put into this variable so that it can be included in
9996 the rejection message.
9998 .vitem &$dnslist_text$&
9999 .cindex "&$dnslist_text$&"
10000 When a client host is found to be on a DNS (black) list, the
10001 contents of any associated TXT record are placed in this variable.
10003 .vitem &$dnslist_value$&
10004 .cindex "&$dnslist_value$&"
10005 When a client host is found to be on a DNS (black) list,
10006 the IP address from the resource record is placed in this variable.
10007 If there are multiple records, all the addresses are included, comma-space
10011 .cindex "&$domain$&"
10012 When an address is being routed, or delivered on its own, this variable
10013 contains the domain. Global address rewriting happens when a message is
10014 received, so the value of &$domain$& during routing and delivery is the value
10015 after rewriting. &$domain$& is set during user filtering, but not during system
10016 filtering, because a message may have many recipients and the system filter is
10019 When more than one address is being delivered at once (for example, several
10020 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
10021 have the same domain. Transports can be restricted to handling only one domain
10022 at a time if the value of &$domain$& is required at transport time &-- this is
10023 the default for local transports. For further details of the environment in
10024 which local transports are run, see chapter &<<CHAPenvironment>>&.
10026 .cindex "&%delay_warning_condition%&"
10027 At the end of a delivery, if all deferred addresses have the same domain, it is
10028 set in &$domain$& during the expansion of &%delay_warning_condition%&.
10030 The &$domain$& variable is also used in some other circumstances:
10033 When an ACL is running for a RCPT command, &$domain$& contains the domain of
10034 the recipient address. The domain of the &'sender'& address is in
10035 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
10036 normally set during the running of the MAIL ACL. However, if the sender address
10037 is verified with a callout during the MAIL ACL, the sender domain is placed in
10038 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
10039 the &(smtp)& transport.
10042 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10043 &$domain$& contains the domain portion of the address that is being rewritten;
10044 it can be used in the expansion of the replacement address, for example, to
10045 rewrite domains by file lookup.
10048 With one important exception, whenever a domain list is being scanned,
10049 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
10050 a &%sender_domains%& condition in an ACL is being processed, the subject domain
10051 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
10052 that, in a RCPT ACL, the sender domain list can be dependent on the
10053 recipient domain (which is what is in &$domain$& at this time).
10056 .cindex "ETRN" "value of &$domain$&"
10057 .cindex "&%smtp_etrn_command%&"
10058 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
10059 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
10063 .vitem &$domain_data$&
10064 .cindex "&$domain_data$&"
10065 When the &%domains%& option on a router matches a domain by
10066 means of a lookup, the data read by the lookup is available during the running
10067 of the router as &$domain_data$&. In addition, if the driver routes the
10068 address to a transport, the value is available in that transport. If the
10069 transport is handling multiple addresses, the value from the first address is
10072 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
10073 domain by means of a lookup. The data read by the lookup is available during
10074 the rest of the ACL statement. In all other situations, this variable expands
10077 .vitem &$exim_gid$&
10078 .cindex "&$exim_gid$&"
10079 This variable contains the numerical value of the Exim group id.
10081 .vitem &$exim_path$&
10082 .cindex "&$exim_path$&"
10083 This variable contains the path to the Exim binary.
10085 .vitem &$exim_uid$&
10086 .cindex "&$exim_uid$&"
10087 This variable contains the numerical value of the Exim user id.
10089 .vitem &$found_extension$&
10090 .cindex "&$found_extension$&"
10091 This variable is available when Exim is compiled with the
10092 content-scanning extension and the obsolete &%demime%& condition. For details,
10093 see section &<<SECTdemimecond>>&.
10095 .vitem &$header_$&<&'name'&>
10096 This is not strictly an expansion variable. It is expansion syntax for
10097 inserting the message header line with the given name. Note that the name must
10098 be terminated by colon or white space, because it may contain a wide variety of
10099 characters. Note also that braces must &'not'& be used.
10103 When the &%check_local_user%& option is set for a router, the user's home
10104 directory is placed in &$home$& when the check succeeds. In particular, this
10105 means it is set during the running of users' filter files. A router may also
10106 explicitly set a home directory for use by a transport; this can be overridden
10107 by a setting on the transport itself.
10109 When running a filter test via the &%-bf%& option, &$home$& is set to the value
10110 of the environment variable HOME.
10114 When the &(smtp)& transport is expanding its options for encryption using TLS,
10115 &$host$& contains the name of the host to which it is connected. Likewise, when
10116 used in the client part of an authenticator configuration (see chapter
10117 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
10118 client is connected.
10120 .cindex "transport" "filter"
10121 .cindex "filter" "transport filter"
10122 When used in a transport filter (see chapter &<<CHAPtransportgeneric>>&)
10123 &$host$& refers to the host involved in the current connection. When a local
10124 transport is run as a result of a router that sets up a host list, &$host$&
10125 contains the name of the first host.
10127 .vitem &$host_address$&
10128 .cindex "&$host_address$&"
10129 This variable is set to the remote host's IP address whenever &$host$& is set
10130 for a remote connection. It is also set to the IP address that is being checked
10131 when the &%ignore_target_hosts%& option is being processed.
10133 .vitem &$host_data$&
10134 .cindex "&$host_data$&"
10135 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
10136 result of the lookup is made available in the &$host_data$& variable. This
10137 allows you, for example, to do things like this:
10139 deny hosts = net-lsearch;/some/file
10140 message = $host_data
10142 .vitem &$host_lookup_deferred$&
10143 .cindex "host name lookup" "failure of"
10144 .cindex "&$host_lookup_deferred$&"
10145 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
10146 message comes from a remote host and there is an attempt to look up the host's
10147 name from its IP address, and the attempt is not successful, one of these
10148 variables is set to &"1"&.
10151 If the lookup receives a definite negative response (for example, a DNS lookup
10152 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
10155 If there is any kind of problem during the lookup, such that Exim cannot
10156 tell whether or not the host name is defined (for example, a timeout for a DNS
10157 lookup), &$host_lookup_deferred$& is set to &"1"&.
10160 Looking up a host's name from its IP address consists of more than just a
10161 single reverse lookup. Exim checks that a forward lookup of at least one of the
10162 names it receives from a reverse lookup yields the original IP address. If this
10163 is not the case, Exim does not accept the looked up name(s), and
10164 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
10165 IP address (for example, the existence of a PTR record in the DNS) is not
10166 sufficient on its own for the success of a host name lookup. If the reverse
10167 lookup succeeds, but there is a lookup problem such as a timeout when checking
10168 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
10169 &"1"&. See also &$sender_host_name$&.
10171 .vitem &$host_lookup_failed$&
10172 .cindex "&$host_lookup_failed$&"
10173 See &$host_lookup_deferred$&.
10177 .cindex "&$inode$&"
10178 The only time this variable is set is while expanding the &%directory_file%&
10179 option in the &(appendfile)& transport. The variable contains the inode number
10180 of the temporary file which is about to be renamed. It can be used to construct
10181 a unique name for the file.
10183 .vitem &$interface_address$&
10184 .cindex "&$interface_address$&"
10185 As soon as a server starts processing a TCP/IP connection, this variable is set
10186 to the address of the local IP interface, and &$interface_port$& is set to the
10187 port number. These values are therefore available for use in the &"connect"&
10188 ACL. See also the &%-oMi%& command line option. As well as being used in ACLs,
10189 these variable could be used, for example, to make the file name for a TLS
10190 certificate depend on which interface and/or port is being used.
10192 .vitem &$interface_port$&
10193 .cindex "&$interface_port$&"
10194 See &$interface_address$&.
10197 .cindex "&$ldap_dn$&"
10198 This variable, which is available only when Exim is compiled with LDAP support,
10199 contains the DN from the last entry in the most recently successful LDAP
10202 .vitem &$load_average$&
10203 .cindex "&$load_average$&"
10204 This variable contains the system load average, multiplied by 1000 to that it
10205 is an integer. For example, if the load average is 0.21, the value of the
10206 variable is 210. The value is recomputed every time the variable is referenced.
10208 .vitem &$local_part$&
10209 .cindex "&$local_part$&"
10210 When an address is being routed, or delivered on its own, this
10211 variable contains the local part. When a number of addresses are being
10212 delivered together (for example, multiple RCPT commands in an SMTP
10213 session), &$local_part$& is not set.
10215 Global address rewriting happens when a message is received, so the value of
10216 &$local_part$& during routing and delivery is the value after rewriting.
10217 &$local_part$& is set during user filtering, but not during system filtering,
10218 because a message may have many recipients and the system filter is called just
10221 .cindex "&$local_part_prefix$&"
10222 .cindex "&$local_part_suffix$&"
10223 If a local part prefix or suffix has been recognized, it is not included in the
10224 value of &$local_part$& during routing and subsequent delivery. The values of
10225 any prefix or suffix are in &$local_part_prefix$& and
10226 &$local_part_suffix$&, respectively.
10228 When a message is being delivered to a file, pipe, or autoreply transport as a
10229 result of aliasing or forwarding, &$local_part$& is set to the local part of
10230 the parent address, not to the file name or command (see &$address_file$& and
10233 When an ACL is running for a RCPT command, &$local_part$& contains the
10234 local part of the recipient address.
10236 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10237 &$local_part$& contains the local part of the address that is being rewritten;
10238 it can be used in the expansion of the replacement address, for example.
10240 In all cases, all quoting is removed from the local part. For example, for both
10243 "abc:xyz"@test.example
10244 abc\:xyz@test.example
10246 the value of &$local_part$& is
10250 If you use &$local_part$& to create another address, you should always wrap it
10251 inside a quoting operator. For example, in a &(redirect)& router you could
10254 data = ${quote_local_part:$local_part}@new.domain.example
10256 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
10257 to process local parts in a case-dependent manner in a router, you can set the
10258 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
10260 .vitem &$local_part_data$&
10261 .cindex "&$local_part_data$&"
10262 When the &%local_parts%& option on a router matches a local part by means of a
10263 lookup, the data read by the lookup is available during the running of the
10264 router as &$local_part_data$&. In addition, if the driver routes the address
10265 to a transport, the value is available in that transport. If the transport is
10266 handling multiple addresses, the value from the first address is used.
10268 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
10269 matches a local part by means of a lookup. The data read by the lookup is
10270 available during the rest of the ACL statement. In all other situations, this
10271 variable expands to nothing.
10273 .vitem &$local_part_prefix$&
10274 .cindex "&$local_part_prefix$&"
10275 When an address is being routed or delivered, and a
10276 specific prefix for the local part was recognized, it is available in this
10277 variable, having been removed from &$local_part$&.
10279 .vitem &$local_part_suffix$&
10280 .cindex "&$local_part_suffix$&"
10281 When an address is being routed or delivered, and a
10282 specific suffix for the local part was recognized, it is available in this
10283 variable, having been removed from &$local_part$&.
10285 .vitem &$local_scan_data$&
10286 .cindex "&$local_scan_data$&"
10287 This variable contains the text returned by the &[local_scan()]& function when
10288 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
10290 .vitem &$local_user_gid$&
10291 .cindex "&$local_user_gid$&"
10292 See &$local_user_uid$&.
10294 .vitem &$local_user_uid$&
10295 .cindex "&$local_user_uid$&"
10296 This variable and &$local_user_gid$& are set to the uid and gid after the
10297 &%check_local_user%& router precondition succeeds. This means that their values
10298 are available for the remaining preconditions (&%senders%&, &%require_files%&,
10299 and &%condition%&), for the &%address_data%& expansion, and for any
10300 router-specific expansions. At all other times, the values in these variables
10301 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
10303 .vitem &$localhost_number$&
10304 .cindex "&$localhost_number$&"
10305 This contains the expanded value of the
10306 &%localhost_number%& option. The expansion happens after the main options have
10309 .vitem &$log_inodes$&
10310 .cindex "&$log_inodes$&"
10311 The number of free inodes in the disk partition where Exim's
10312 log files are being written. The value is recalculated whenever the variable is
10313 referenced. If the relevant file system does not have the concept of inodes,
10314 the value of is -1. See also the &%check_log_inodes%& option.
10316 .vitem &$log_space$&
10317 .cindex "&$log_space$&"
10318 The amount of free space (as a number of kilobytes) in the disk
10319 partition where Exim's log files are being written. The value is recalculated
10320 whenever the variable is referenced. If the operating system does not have the
10321 ability to find the amount of free space (only true for experimental systems),
10322 the space value is -1. See also the &%check_log_space%& option.
10325 .vitem &$mailstore_basename$&
10326 .cindex "&$mailstore_basename$&"
10327 This variable is set only when doing deliveries in &"mailstore"& format in the
10328 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
10329 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
10330 contains the basename of the files that are being written, that is, the name
10331 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
10334 .vitem &$malware_name$&
10335 .cindex "&$malware_name$&"
10336 This variable is available when Exim is compiled with the
10337 content-scanning extension. It is set to the name of the virus that was found
10338 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
10341 .vitem &$message_age$&
10342 .cindex "message" "age of"
10343 .cindex "&$message_age$&"
10344 This variable is set at the start of a delivery attempt to contain the number
10345 of seconds since the message was received. It does not change during a single
10348 .vitem &$message_body$&
10349 .cindex "body of message" "expansion variable"
10350 .cindex "message body" "in expansion"
10351 .cindex "binary zero" "in message body"
10352 .cindex "&$message_body$&"
10353 This variable contains the initial portion of a message's
10354 body while it is being delivered, and is intended mainly for use in filter
10355 files. The maximum number of characters of the body that are put into the
10356 variable is set by the &%message_body_visible%& configuration option; the
10357 default is 500. Newlines are converted into spaces to make it easier to search
10358 for phrases that might be split over a line break.
10359 Binary zeros are also converted into spaces.
10361 .vitem &$message_body_end$&
10362 .cindex "body of message" "expansion variable"
10363 .cindex "message body" "in expansion"
10364 .cindex "&$message_body_end$&"
10365 This variable contains the final portion of a message's
10366 body while it is being delivered. The format and maximum size are as for
10369 .vitem &$message_body_size$&
10370 .cindex "body of message" "size"
10371 .cindex "message body" "size"
10372 .cindex "&$message_body_size$&"
10373 When a message is being delivered, this variable contains the size of the body
10374 in bytes. The count starts from the character after the blank line that
10375 separates the body from the header. Newlines are included in the count. See
10376 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
10378 .vitem &$message_exim_id$&
10379 .cindex "&$message_exim_id$&"
10380 When a message is being received or delivered, this variable contains the
10381 unique message id that is generated and used by Exim to identify the message.
10382 An id is not created for a message until after its header has been successfully
10383 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
10384 line; it is the local id that Exim assigns to the message, for example:
10385 &`1BXTIK-0001yO-VA`&.
10387 .vitem &$message_headers$&
10388 This variable contains a concatenation of all the header lines when a message
10389 is being processed, except for lines added by routers or transports. The header
10390 lines are separated by newline characters.
10392 .vitem &$message_id$&
10393 This is an old name for &$message_exim_id$&, which is now deprecated.
10395 .vitem &$message_linecount$&
10396 .cindex "&$message_linecount$&"
10397 This variable contains the total number of lines in the header and body of the
10398 message. Compare &$body_linecount$&, which is the count for the body only.
10399 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
10400 number of lines received. Before delivery happens (that is, before filters,
10401 routers, and transports run) the count is increased to include the
10402 &'Received:'& header line that Exim standardly adds, and also any other header
10403 lines that are added by ACLs. The blank line that separates the message header
10404 from the body is not counted. Here is an example of the use of this variable in
10407 deny message = Too many lines in message header
10409 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
10411 In the MAIL and RCPT ACLs, the value is zero because at that stage the
10412 message has not yet been received.
10414 .vitem &$message_size$&
10415 .cindex "size" "of message"
10416 .cindex "message" "size"
10417 .cindex "&$message_size$&"
10418 When a message is being processed, this variable contains its size in bytes. In
10419 most cases, the size includes those headers that were received with the
10420 message, but not those (such as &'Envelope-to:'&) that are added to individual
10421 deliveries as they are written. However, there is one special case: during the
10422 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
10423 doing a delivery in maildir format, the value of &$message_size$& is the
10424 precise size of the file that has been written. See also
10425 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
10427 .cindex "RCPT" "value of &$message_size$&"
10428 While running an ACL at the time of an SMTP RCPT command, &$message_size$&
10429 contains the size supplied on the MAIL command, or -1 if no size was given. The
10430 value may not, of course, be truthful.
10432 .vitem &$mime_$&&'xxx'&
10433 A number of variables whose names start with &$mime$& are
10434 available when Exim is compiled with the content-scanning extension. For
10435 details, see section &<<SECTscanmimepart>>&.
10437 .vitem "&$n0$& &-- &$n9$&"
10438 These variables are counters that can be incremented by means
10439 of the &%add%& command in filter files.
10441 .vitem &$original_domain$&
10442 .cindex "&$domain$&"
10443 .cindex "&$original_domain$&"
10444 When a top-level address is being processed for delivery, this contains the
10445 same value as &$domain$&. However, if a &"child"& address (for example,
10446 generated by an alias, forward, or filter file) is being processed, this
10447 variable contains the domain of the original address. This differs from
10448 &$parent_domain$& only when there is more than one level of aliasing or
10449 forwarding. When more than one address is being delivered in a single transport
10450 run, &$original_domain$& is not set.
10452 If a new address is created by means of a &%deliver%& command in a system
10453 filter, it is set up with an artificial &"parent"& address. This has the local
10454 part &'system-filter'& and the default qualify domain.
10456 .vitem &$original_local_part$&
10457 .cindex "&$local_part$&"
10458 .cindex "&$original_local_part$&"
10459 When a top-level address is being processed for delivery, this contains the
10460 same value as &$local_part$&, unless a prefix or suffix was removed from the
10461 local part, because &$original_local_part$& always contains the full local
10462 part. When a &"child"& address (for example, generated by an alias, forward, or
10463 filter file) is being processed, this variable contains the full local part of
10464 the original address.
10466 If the router that did the redirection processed the local part
10467 case-insensitively, the value in &$original_local_part$& is in lower case.
10468 This variable differs from &$parent_local_part$& only when there is more than
10469 one level of aliasing or forwarding. When more than one address is being
10470 delivered in a single transport run, &$original_local_part$& is not set.
10472 If a new address is created by means of a &%deliver%& command in a system
10473 filter, it is set up with an artificial &"parent"& address. This has the local
10474 part &'system-filter'& and the default qualify domain.
10476 .vitem &$originator_gid$&
10477 .cindex "gid (group id)" "of originating user"
10478 .cindex "sender" "gid"
10479 .cindex "&$caller_gid$&"
10480 .cindex "&$originator_gid$&"
10481 This variable contains the value of &$caller_gid$& that was set when the
10482 message was received. For messages received via the command line, this is the
10483 gid of the sending user. For messages received by SMTP over TCP/IP, this is
10484 normally the gid of the Exim user.
10486 .vitem &$originator_uid$&
10487 .cindex "uid (user id)" "of originating user"
10488 .cindex "sender" "uid"
10489 .cindex "&$caller_uid$&"
10490 .cindex "&$originaltor_uid$&"
10491 The value of &$caller_uid$& that was set when the message was received. For
10492 messages received via the command line, this is the uid of the sending user.
10493 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
10496 .vitem &$parent_domain$&
10497 .cindex "&$parent_domain$&"
10498 This variable is similar to &$original_domain$& (see
10499 above), except that it refers to the immediately preceding parent address.
10501 .vitem &$parent_local_part$&
10502 .cindex "&$parent_local_part$&"
10503 This variable is similar to &$original_local_part$&
10504 (see above), except that it refers to the immediately preceding parent address.
10507 .cindex "pid (process id)" "of current process"
10509 This variable contains the current process id.
10511 .vitem &$pipe_addresses$&
10512 .cindex "filter" "transport filter"
10513 .cindex "transport" "filter"
10514 .cindex "&$pipe_addresses$&"
10515 This is not an expansion variable, but is mentioned here because the string
10516 &"$pipe_addresses"& is handled specially in the command specification for the
10517 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
10518 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
10519 It cannot be used in general expansion strings, and provokes an &"unknown
10520 variable"& error if encountered.
10522 .vitem &$primary_hostname$&
10523 .cindex "&$primary_hostname$&"
10524 This variable contains the value set by &%primary_hostname%& in the
10525 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
10526 a single-component name, Exim calls &[gethostbyname()]& (or
10527 &[getipnodebyname()]& where available) in an attempt to acquire a fully
10528 qualified host name. See also &$smtp_active_hostname$&.
10531 .vitem &$prvscheck_address$&
10532 This variable is used in conjunction with the &%prvscheck%& expansion item,
10533 which is described in sections &<<SECTexpansionitems>>& and
10534 &<<SECTverifyPRVS>>&.
10536 .vitem &$prvscheck_keynum$&
10537 This variable is used in conjunction with the &%prvscheck%& expansion item,
10538 which is described in sections &<<SECTexpansionitems>>& and
10539 &<<SECTverifyPRVS>>&.
10541 .vitem &$prvscheck_result$&
10542 This variable is used in conjunction with the &%prvscheck%& expansion item,
10543 which is described in sections &<<SECTexpansionitems>>& and
10544 &<<SECTverifyPRVS>>&.
10546 .vitem &$qualify_domain$&
10547 .cindex "&$qualify_domain$&"
10548 The value set for the &%qualify_domain%& option in the configuration file.
10550 .vitem &$qualify_recipient$&
10551 .cindex "&$qualify_recipient$&"
10552 The value set for the &%qualify_recipient%& option in the configuration file,
10553 or if not set, the value of &$qualify_domain$&.
10555 .vitem &$rcpt_count$&
10556 .cindex "&$rcpt_count$&"
10557 When a message is being received by SMTP, this variable contains the number of
10558 RCPT commands received for the current message. If this variable is used in a
10559 RCPT ACL, its value includes the current command.
10561 .vitem &$rcpt_defer_count$&
10562 .cindex "&$rcpt_defer_count$&"
10563 When a message is being received by SMTP, this variable contains the number of
10564 RCPT commands in the current message that have previously been rejected with a
10565 temporary (4&'xx'&) response.
10567 .vitem &$rcpt_fail_count$&
10568 .cindex "&$rcpt_fail_count$&"
10569 When a message is being received by SMTP, this variable contains the number of
10570 RCPT commands in the current message that have previously been rejected with a
10571 permanent (5&'xx'&) response.
10573 .vitem &$received_count$&
10574 .cindex "&$received_count$&"
10575 This variable contains the number of &'Received:'& header lines in the message,
10576 including the one added by Exim (so its value is always greater than zero). It
10577 is available in the DATA ACL, the non-SMTP ACL, and while routing and
10580 .vitem &$received_for$&
10581 .cindex "&$received_for$&"
10582 If there is only a single recipient address in an incoming message, this
10583 variable contains that address when the &'Received:'& header line is being
10584 built. The value is copied after recipient rewriting has happened, but before
10585 the &[local_scan()]& function is run.
10587 .vitem &$received_protocol$&
10588 .cindex "&$received_protocol$&"
10589 When a message is being processed, this variable contains the name of the
10590 protocol by which it was received. Most of the names used by Exim are defined
10591 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
10592 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
10593 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
10594 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
10595 connection and the client was successfully authenticated.
10597 Exim uses the protocol name &"smtps"& for the case when encryption is
10598 automatically set up on connection without the use of STARTTLS (see
10599 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
10600 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
10601 where the client initially uses EHLO, sets up an encrypted connection using
10602 STARTTLS, and then uses HELO afterwards.
10604 The &%-oMr%& option provides a way of specifying a custom protocol name for
10605 messages that are injected locally by trusted callers. This is commonly used to
10606 identify messages that are being re-injected after some kind of scanning.
10608 .vitem &$received_time$&
10609 .cindex "&$received_time$&"
10610 This variable contains the date and time when the current message was received,
10611 as a number of seconds since the start of the Unix epoch.
10613 .vitem &$recipient_data$&
10614 .cindex "&$recipient_data$&"
10615 This variable is set after an indexing lookup success in an ACL &%recipients%&
10616 condition. It contains the data from the lookup, and the value remains set
10617 until the next &%recipients%& test. Thus, you can do things like this:
10619 &`require recipients = cdb*@;/some/file`&
10620 &`deny `&&'some further test involving'& &`$recipient_data`&
10622 &*Warning*&: This variable is set only when a lookup is used as an indexing
10623 method in the address list, using the semicolon syntax as in the example above.
10624 The variable is not set for a lookup that is used as part of the string
10625 expansion that all such lists undergo before being interpreted.
10627 .vitem &$recipient_verify_failure$&
10628 .cindex "&$recipient_verify_failure$&"
10629 In an ACL, when a recipient verification fails, this variable contains
10630 information about the failure. It is set to one of the following words:
10633 &"qualify"&: The address was unqualified (no domain), and the message
10634 was neither local nor came from an exempted host.
10637 &"route"&: Routing failed.
10640 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
10641 or before the MAIL command (that is, on initial connection, HELO, or
10645 &"recipient"&: The RCPT command in a callout was rejected.
10648 &"postmaster"&: The postmaster check in a callout was rejected.
10651 The main use of this variable is expected to be to distinguish between
10652 rejections of MAIL and rejections of RCPT.
10654 .vitem &$recipients$&
10655 .cindex "&$recipients$&"
10656 This variable contains a list of envelope recipients for a
10657 message. A comma and a space separate the addresses in the replacement text.
10658 However, the variable is not generally available, to prevent exposure of Bcc
10659 recipients in unprivileged users' filter files. You can use &$recipients$& only
10660 in these two cases:
10663 In a system filter file.
10665 In the ACLs associated with the DATA command, that is, the ACLs defined by
10666 &%acl_smtp_predata%& and &%acl_smtp_data%&.
10670 .vitem &$recipients_count$&
10671 .cindex "&$recipients_count$&"
10672 When a message is being processed, this variable contains the number of
10673 envelope recipients that came with the message. Duplicates are not excluded
10674 from the count. While a message is being received over SMTP, the number
10675 increases for each accepted recipient. It can be referenced in an ACL.
10677 .vitem &$reply_address$&
10678 .cindex "&$reply_address$&"
10679 When a message is being processed, this variable contains the contents of the
10680 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
10681 contents of the &'From:'& header line. &new("Apart from the removal of leading
10682 white space, the value is not processed in any way. In particular, no RFC 2047
10683 decoding or character code translation takes place.")
10685 .vitem &$return_path$&
10686 .cindex "&$return_path$&"
10687 When a message is being delivered, this variable contains the return path &--
10688 the sender field that will be sent as part of the envelope. It is not enclosed
10689 in <> characters. At the start of routing an address, &$return_path$& has the
10690 same value as &$sender_address$&, but if, for example, an incoming message to a
10691 mailing list has been expanded by a router which specifies a different address
10692 for bounce messages, &$return_path$& subsequently contains the new bounce
10693 address, whereas &$sender_address$& always contains the original sender address
10694 that was received with the message. In other words, &$sender_address$& contains
10695 the incoming envelope sender, and &$return_path$& contains the outgoing
10698 .vitem &$return_size_limit$&
10699 .cindex "&$return_size_limit$&"
10700 This is an obsolete name for &$bounce_return_size_limit$&.
10703 .cindex "return code" "from &%run%& expansion"
10704 .cindex "&$runrc$&"
10705 This variable contains the return code from a command that is run by the
10706 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
10707 assume the order in which option values are expanded, except for those
10708 preconditions whose order of testing is documented. Therefore, you cannot
10709 reliably expect to set &$runrc$& by the expansion of one option, and use it in
10712 .vitem &$self_hostname$&
10713 .cindex "&%self%& option" "value of host name"
10714 .cindex "&$self_hostname$&"
10715 When an address is routed to a supposedly remote host that turns out to be the
10716 local host, what happens is controlled by the &%self%& generic router option.
10717 One of its values causes the address to be passed to another router. When this
10718 happens, &$self_hostname$& is set to the name of the local host that the
10719 original router encountered. In other circumstances its contents are null.
10721 .vitem &$sender_address$&
10722 .cindex "&$sender_address$&"
10723 When a message is being processed, this variable contains the sender's address
10724 that was received in the message's envelope. For bounce messages, the value of
10725 this variable is the empty string. See also &$return_path$&.
10727 .vitem &$sender_address_data$&
10728 .cindex "&$address_data$&"
10729 .cindex "&$sender_address_data$&"
10730 If &$address_data$& is set when the routers are called from an ACL to verify a
10731 sender address, the final value is preserved in &$sender_address_data$&, to
10732 distinguish it from data from a recipient address. The value does not persist
10733 after the end of the current ACL statement. If you want to preserve it for
10734 longer, you can save it in an ACL variable.
10736 .vitem &$sender_address_domain$&
10737 .cindex "&$sender_address_domain$&"
10738 The domain portion of &$sender_address$&.
10740 .vitem &$sender_address_local_part$&
10741 .cindex "&$sender_address_local_part$&"
10742 The local part portion of &$sender_address$&.
10744 .vitem &$sender_data$&
10745 .cindex "&$sender_data$&"
10746 This variable is set after a lookup success in an ACL &%senders%& condition or
10747 in a router &%senders%& option. It contains the data from the lookup, and the
10748 value remains set until the next &%senders%& test. Thus, you can do things like
10751 &`require senders = cdb*@;/some/file`&
10752 &`deny `&&'some further test involving'& &`$sender_data`&
10754 &*Warning*&: This variable is set only when a lookup is used as an indexing
10755 method in the address list, using the semicolon syntax as in the example above.
10756 The variable is not set for a lookup that is used as part of the string
10757 expansion that all such lists undergo before being interpreted.
10759 .vitem &$sender_fullhost$&
10760 .cindex "&$sender_fullhost$&"
10761 When a message is received from a remote host, this variable contains the host
10762 name and IP address in a single string. It ends with the IP address in square
10763 brackets, followed by a colon and a port number if the logging of ports is
10764 enabled. The format of the rest of the string depends on whether the host
10765 issued a HELO or EHLO SMTP command, and whether the host name was verified by
10766 looking up its IP address. (Looking up the IP address can be forced by the
10767 &%host_lookup%& option, independent of verification.) A plain host name at the
10768 start of the string is a verified host name; if this is not present,
10769 verification either failed or was not requested. A host name in parentheses is
10770 the argument of a HELO or EHLO command. This is omitted if it is identical to
10771 the verified host name or to the host's IP address in square brackets.
10773 .vitem &$sender_helo_name$&
10774 .cindex "&$sender_hslo_name$&"
10775 When a message is received from a remote host that has issued a HELO or EHLO
10776 command, the argument of that command is placed in this variable. It is also
10777 set if HELO or EHLO is used when a message is received using SMTP locally via
10778 the &%-bs%& or &%-bS%& options.
10780 .vitem &$sender_host_address$&
10781 .cindex "&$sender_host_address$&"
10782 When a message is received from a remote host, this variable contains that
10783 host's IP address. For locally submitted messages, it is empty.
10785 .vitem &$sender_host_authenticated$&
10786 .cindex "&$sender_host_authenticated$&"
10787 This variable contains the name (not the public name) of the authenticator
10788 driver that successfully authenticated the client from which the message was
10789 received. It is empty if there was no successful authentication. See also
10790 &$authenticated_id$&.
10792 .vitem &$sender_host_name$&
10793 .cindex "&$sender_host_name$&"
10794 When a message is received from a remote host, this variable contains the
10795 host's name as obtained by looking up its IP address. For messages received by
10796 other means, this variable is empty.
10798 .cindex "&$host_lookup_failed$&"
10799 If the host name has not previously been looked up, a reference to
10800 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
10801 A looked up name is accepted only if it leads back to the original IP address
10802 via a forward lookup. If either the reverse or the forward lookup fails to find
10803 any data, or if the forward lookup does not yield the original IP address,
10804 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
10806 .cindex "&$host_lookup_deferred$&"
10807 However, if either of the lookups cannot be completed (for example, there is a
10808 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
10809 &$host_lookup_failed$& remains set to &"0"&.
10811 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
10812 host name again if there is a subsequent reference to &$sender_host_name$&
10813 in the same Exim process, but it does try again if &$sender_host_deferred$&
10816 Exim does not automatically look up every calling host's name. If you want
10817 maximum efficiency, you should arrange your configuration so that it avoids
10818 these lookups altogether. The lookup happens only if one or more of the
10819 following are true:
10822 A string containing &$sender_host_name$& is expanded.
10824 The calling host matches the list in &%host_lookup%&. In the default
10825 configuration, this option is set to *, so it must be changed if lookups are
10826 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
10828 Exim needs the host name in order to test an item in a host list. The items
10829 that require this are described in sections &<<SECThoslispatnam>>& and
10830 &<<SECThoslispatnamsk>>&.
10832 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
10833 In this case, the host name is required to compare with the name quoted in any
10834 EHLO or HELO commands that the client issues.
10836 The remote host issues a EHLO or HELO command that quotes one of the
10837 domains in &%helo_lookup_domains%&. The default value of this option is
10838 . ==== As this is a nested list, any displays it contains must be indented
10839 . ==== as otherwise they are too far to the left.
10841 helo_lookup_domains = @ : @[]
10843 which causes a lookup if a remote host (incorrectly) gives the server's name or
10844 IP address in an EHLO or HELO command.
10848 .vitem &$sender_host_port$&
10849 .cindex "&$sender_host_port$&"
10850 When a message is received from a remote host, this variable contains the port
10851 number that was used on the remote host.
10853 .vitem &$sender_ident$&
10854 .cindex "&$sender_ident$&"
10855 When a message is received from a remote host, this variable contains the
10856 identification received in response to an RFC 1413 request. When a message has
10857 been received locally, this variable contains the login name of the user that
10860 .vitem &$sender_rate_$&&'xxx'&
10861 A number of variables whose names begin &$sender_rate_$& are set as part of the
10862 &%ratelimit%& ACL condition. Details are given in section
10863 &<<SECTratelimiting>>&.
10865 .vitem &$sender_rcvhost$&
10866 .cindex "DNS" "reverse lookup"
10867 .cindex "reverse DNS lookup"
10868 .cindex "&$sender_rcvhost$&"
10869 This is provided specifically for use in &'Received:'& headers. It starts with
10870 either the verified host name (as obtained from a reverse DNS lookup) or, if
10871 there is no verified host name, the IP address in square brackets. After that
10872 there may be text in parentheses. When the first item is a verified host name,
10873 the first thing in the parentheses is the IP address in square brackets,
10874 followed by a colon and a port number if port logging is enabled. When the
10875 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
10878 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
10879 was used and its argument was not identical to the real host name or IP
10880 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
10881 all three items are present in the parentheses, a newline and tab are inserted
10882 into the string, to improve the formatting of the &'Received:'& header.
10884 .vitem &$sender_verify_failure$&
10885 .cindex "&$sender_verify_failure$&"
10886 In an ACL, when a sender verification fails, this variable contains information
10887 about the failure. The details are the same as for
10888 &$recipient_verify_failure$&.
10890 .vitem &$smtp_active_hostname$&
10891 .cindex "&$smtp_active_hostname$&"
10892 During an SMTP session, this variable contains the value of the active host
10893 name, as specified by the &%smtp_active_hostname%& option. The value of
10894 &$smtp_active_hostname$& is saved with any message that is received, so its
10895 value can be consulted during routing and delivery.
10897 .vitem &$smtp_command$&
10898 .cindex "&$smtp_command$&"
10899 During the processing of an incoming SMTP command, this variable contains the
10900 entire command. This makes it possible to distinguish between HELO and EHLO in
10901 the HELO ACL, and also to distinguish between commands such as these:
10906 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
10907 command, the address in &$smtp_command$& is the original address before any
10908 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
10909 the address after SMTP-time rewriting.
10911 .vitem &$smtp_command_argument$&
10912 .cindex "SMTP command" "argument for"
10913 .cindex "&$smtp_command_argument$&"
10914 While an ACL is running to check an SMTP command, this variable contains the
10915 argument, that is, the text that follows the command name, with leading white
10916 space removed. Following the introduction of &$smtp_command$&, this variable is
10917 somewhat redundant, but is retained for backwards compatibility.
10919 .vitem "&$sn0$& &-- &$sn9$&"
10920 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
10921 that were current at the end of the system filter file. This allows a system
10922 filter file to set values that can be tested in users' filter files. For
10923 example, a system filter could set a value indicating how likely it is that a
10924 message is junk mail.
10926 .vitem &$spam_$&&'xxx'&
10927 A number of variables whose names start with &$spam$& are available when Exim
10928 is compiled with the content-scanning extension. For details, see section
10929 &<<SECTscanspamass>>&.
10932 .vitem &$spool_directory$&
10933 .cindex "&$spool_directory$&"
10934 The name of Exim's spool directory.
10936 .vitem &$spool_inodes$&
10937 .cindex "&$spool_inodes$&"
10938 The number of free inodes in the disk partition where Exim's spool files are
10939 being written. The value is recalculated whenever the variable is referenced.
10940 If the relevant file system does not have the concept of inodes, the value of
10941 is -1. See also the &%check_spool_inodes%& option.
10943 .vitem &$spool_space$&
10944 .cindex "&$spool_space$&"
10945 The amount of free space (as a number of kilobytes) in the disk partition where
10946 Exim's spool files are being written. The value is recalculated whenever the
10947 variable is referenced. If the operating system does not have the ability to
10948 find the amount of free space (only true for experimental systems), the space
10949 value is -1. For example, to check in an ACL that there is at least 50
10950 megabytes free on the spool, you could write:
10952 condition = ${if > {$spool_space}{50000}}
10954 See also the &%check_spool_space%& option.
10957 .vitem &$thisaddress$&
10958 .cindex "&$thisaddress$&"
10959 This variable is set only during the processing of the &%foranyaddress%&
10960 command in a filter file. Its use is explained in the description of that
10961 command, which can be found in the separate document entitled &'Exim's
10962 interfaces to mail filtering'&.
10964 .vitem &$tls_certificate_verified$&
10965 .cindex "&$tls_certificate_verified$&"
10966 This variable is set to &"1"& if a TLS certificate was verified when the
10967 message was received, and &"0"& otherwise.
10969 .vitem &$tls_cipher$&
10970 .cindex "&$tls_cipher$&"
10971 When a message is received from a remote host over an encrypted SMTP
10972 connection, this variable is set to the cipher suite that was negotiated, for
10973 example DES-CBC3-SHA. In other circumstances, in particular, for message
10974 received over unencrypted connections, the variable is empty. See chapter
10975 &<<CHAPTLS>>& for details of TLS support.
10977 .vitem &$tls_peerdn$&
10978 .cindex "&$tls_peerdn$&"
10979 When a message is received from a remote host over an encrypted SMTP
10980 connection, and Exim is configured to request a certificate from the client,
10981 the value of the Distinguished Name of the certificate is made available in the
10982 &$tls_peerdn$& during subsequent processing.
10984 .vitem &$tod_bsdinbox$&
10985 .cindex "&$tod_bsdinbox$&"
10986 The time of day and the date, in the format required for BSD-style mailbox
10987 files, for example: Thu Oct 17 17:14:09 1995.
10989 .vitem &$tod_epoch$&
10990 .cindex "&$tod_epoch$&"
10991 The time and date as a number of seconds since the start of the Unix epoch.
10993 .vitem &$tod_full$&
10994 .cindex "&$tod_full$&"
10995 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
10996 +0100. The timezone is always given as a numerical offset from UTC, with
10997 positive values used for timezones that are ahead (east) of UTC, and negative
10998 values for those that are behind (west).
11001 .cindex "&$tod_log$&"
11002 The time and date in the format used for writing Exim's log files, for example:
11003 1995-10-12 15:32:29, but without a timezone.
11005 .vitem &$tod_logfile$&
11006 .cindex "&$tod_logfile$&"
11007 This variable contains the date in the format yyyymmdd. This is the format that
11008 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
11011 .vitem &$tod_zone$&
11012 .cindex "&$tod_zone$&"
11013 This variable contains the numerical value of the local timezone, for example:
11016 .vitem &$tod_zulu$&
11017 .cindex "&$tod_zulu$&"
11018 This variable contains the UTC date and time in &"Zulu"& format, as specified
11019 by ISO 8601, for example: 20030221154023Z.
11022 .cindex "&$value$&"
11023 This variable contains the result of an expansion lookup, extraction operation,
11024 or external command, as described above.
11026 .vitem &$version_number$&
11027 .cindex "&$version_number$&"
11028 The version number of Exim.
11030 .vitem &$warn_message_delay$&
11031 .cindex "&$warn_message_delay$&"
11032 This variable is set only during the creation of a message warning about a
11033 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11035 .vitem &$warn_message_recipients$&
11036 .cindex "&$warn_message_recipients$&"
11037 This variable is set only during the creation of a message warning about a
11038 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11044 . ////////////////////////////////////////////////////////////////////////////
11045 . ////////////////////////////////////////////////////////////////////////////
11047 .chapter "Embedded Perl" "CHAPperl"
11048 .scindex IIDperl "Perl" "calling from Exim"
11049 Exim can be built to include an embedded Perl interpreter. When this is done,
11050 Perl subroutines can be called as part of the string expansion process. To make
11051 use of the Perl support, you need version 5.004 or later of Perl installed on
11052 your system. To include the embedded interpreter in the Exim binary, include
11057 in your &_Local/Makefile_& and then build Exim in the normal way.
11060 .section "Setting up so Perl can be used"
11061 .cindex "&%perl_startup%&"
11062 Access to Perl subroutines is via a global configuration option called
11063 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
11064 no &%perl_startup%& option in the Exim configuration file then no Perl
11065 interpreter is started and there is almost no overhead for Exim (since none of
11066 the Perl library will be paged in unless used). If there is a &%perl_startup%&
11067 option then the associated value is taken to be Perl code which is executed in
11068 a newly created Perl interpreter.
11070 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
11071 need backslashes before any characters to escape special meanings. The option
11072 should usually be something like
11074 perl_startup = do '/etc/exim.pl'
11076 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
11077 use from Exim. Exim can be configured either to start up a Perl interpreter as
11078 soon as it is entered, or to wait until the first time it is needed. Starting
11079 the interpreter at the beginning ensures that it is done while Exim still has
11080 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
11081 fact used in a particular run. Also, note that this does not mean that Exim is
11082 necessarily running as root when Perl is called at a later time. By default,
11083 the interpreter is started only when it is needed, but this can be changed in
11087 .cindex "&%perl_at_start%&"
11088 Setting &%perl_at_start%& (a boolean option) in the configuration requests
11089 a startup when Exim is entered.
11091 The command line option &%-ps%& also requests a startup when Exim is entered,
11092 overriding the setting of &%perl_at_start%&.
11095 There is also a command line option &%-pd%& (for delay) which suppresses the
11096 initial startup, even if &%perl_at_start%& is set.
11099 .section "Calling Perl subroutines"
11100 When the configuration file includes a &%perl_startup%& option you can make use
11101 of the string expansion item to call the Perl subroutines that are defined
11102 by the &%perl_startup%& code. The operator is used in any of the following
11106 ${perl{foo}{argument}}
11107 ${perl{foo}{argument1}{argument2} ... }
11109 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
11110 arguments may be passed. Passing more than this results in an expansion failure
11111 with an error message of the form
11113 Too many arguments passed to Perl subroutine "foo" (max is 8)
11115 The return value of the Perl subroutine is evaluated in a scalar context before
11116 it is passed back to Exim to be inserted into the expanded string. If the
11117 return value is &'undef'&, the expansion is forced to fail in the same way as
11118 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
11119 by obeying Perl's &%die%& function, the expansion fails with the error message
11120 that was passed to &%die%&.
11123 .section "Calling Exim functions from Perl"
11124 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
11125 is available to call back into Exim's string expansion function. For example,
11128 my $lp = Exim::expand_string('$local_part');
11130 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
11131 Note those are single quotes and not double quotes to protect against
11132 &$local_part$& being interpolated as a Perl variable.
11134 If the string expansion is forced to fail by a &"fail"& item, the result of
11135 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
11136 expansion string, the Perl call from the original expansion string fails with
11137 an appropriate error message, in the same way as if &%die%& were used.
11139 .cindex "debugging" "from embedded Perl"
11140 .cindex "log" "writing from embedded Perl"
11141 Two other Exim functions are available for use from within Perl code.
11142 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
11143 debugging is enabled. If you want a newline at the end, you must supply it.
11144 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
11145 timestamp. In this case, you should not supply a terminating newline.
11148 .section "Use of standard output and error by Perl"
11149 .cindex "Perl" "standard output and error"
11150 You should not write to the standard error or output streams from within your
11151 Perl code, as it is not defined how these are set up. In versions of Exim
11152 before 4.50, it is possible for the standard output or error to refer to the
11153 SMTP connection during message reception via the daemon. Writing to this stream
11154 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
11155 error streams are connected to &_/dev/null_& in the daemon. The chaos is
11156 avoided, but the output is lost.
11158 .cindex "Perl" "use of &%warn%&"
11159 The Perl &%warn%& statement writes to the standard error stream by default.
11160 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
11161 you have no control. When Exim starts up the Perl interpreter, it arranges for
11162 output from the &%warn%& statement to be written to the Exim main log. You can
11163 change this by including appropriate Perl magic somewhere in your Perl code.
11164 For example, to discard &%warn%& output completely, you need this:
11166 $SIG{__WARN__} = sub { };
11168 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
11169 example, the code for the subroutine is empty, so it does nothing, but you can
11170 include any Perl code that you like. The text of the &%warn%& message is passed
11171 as the first subroutine argument.
11175 . ////////////////////////////////////////////////////////////////////////////
11176 . ////////////////////////////////////////////////////////////////////////////
11178 .chapter "Starting the daemon and the use of network interfaces" &&&
11179 "CHAPinterfaces" &&&
11180 "Starting the daemon"
11181 .cindex "daemon" "starting"
11182 .cindex "interface" "listening"
11183 .cindex "network interface"
11184 .cindex "interface" "network"
11185 .cindex "IP address" "for listening"
11186 .cindex "daemon" "listening IP addresses"
11187 .cindex "TCP/IP" "setting listening interfaces"
11188 .cindex "TCP/IP" "setting listening ports"
11189 A host that is connected to a TCP/IP network may have one or more physical
11190 hardware network interfaces. Each of these interfaces may be configured as one
11191 or more &"logical"& interfaces, which are the entities that a program actually
11192 works with. Each of these logical interfaces is associated with an IP address.
11193 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
11194 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
11195 knowledge about the host's interfaces for use in three different circumstances:
11198 When a listening daemon is started, Exim needs to know which interfaces
11199 and ports to listen on.
11201 When Exim is routing an address, it needs to know which IP addresses
11202 are associated with local interfaces. This is required for the correct
11203 processing of MX lists by removing the local host and others with the
11204 same or higher priority values. Also, Exim needs to detect cases
11205 when an address is routed to an IP address that in fact belongs to the
11206 local host. Unless the &%self%& router option or the &%allow_localhost%&
11207 option of the smtp transport is set (as appropriate), this is treated
11208 as an error situation.
11210 When Exim connects to a remote host, it may need to know which interface to use
11211 for the outgoing connection.
11215 Exim's default behaviour is likely to be appropriate in the vast majority
11216 of cases. If your host has only one interface, and you want all its IP
11217 addresses to be treated in the same way, and you are using only the
11218 standard SMTP port, you should not need to take any special action. The
11219 rest of this chapter does not apply to you.
11221 In a more complicated situation you may want to listen only on certain
11222 interfaces, or on different ports, and for this reason there are a number of
11223 options that can be used to influence Exim's behaviour. The rest of this
11224 chapter describes how they operate.
11226 When a message is received over TCP/IP, the interface and port that were
11227 actually used are set in &$interface_address$& and &$interface_port$&.
11231 .section "Starting a listening daemon"
11232 When a listening daemon is started (by means of the &%-bd%& command line
11233 option), the interfaces and ports on which it listens are controlled by the
11237 &%daemon_smtp_ports%& contains a list of default ports. (For backward
11238 compatibility, this option can also be specified in the singular.)
11240 &%local_interfaces%& contains list of interface IP addresses on which to
11241 listen. Each item may optionally also specify a port.
11244 The default list separator in both cases is a colon, but this can be changed as
11245 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
11246 it is usually best to change the separator to avoid having to double all the
11247 colons. For example:
11249 local_interfaces = <; 127.0.0.1 ; \
11252 3ffe:ffff:836f::fe86:a061
11254 There are two different formats for specifying a port along with an IP address
11255 in &%local_interfaces%&:
11258 The port is added onto the address with a dot separator. For example, to listen
11259 on port 1234 on two different IP addresses:
11261 local_interfaces = <; 192.168.23.65.1234 ; \
11262 3ffe:ffff:836f::fe86:a061.1234
11265 The IP address is enclosed in square brackets, and the port is added
11266 with a colon separator, for example:
11268 local_interfaces = <; [192.168.23.65]:1234 ; \
11269 [3ffe:ffff:836f::fe86:a061]:1234
11273 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
11274 default setting contains just one port:
11276 daemon_smtp_ports = smtp
11278 If more than one port is listed, each interface that does not have its own port
11279 specified listens on all of them. Ports that are listed in
11280 &%daemon_smtp_ports%& can be identified either by name (defined in
11281 &_/etc/services_&) or by number. However, when ports are given with individual
11282 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
11286 .section "Special IP listening addresses"
11287 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
11288 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
11289 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
11290 instead of setting up separate listening sockets for each interface. The
11291 default value of &%local_interfaces%& is
11293 local_interfaces = 0.0.0.0
11295 when Exim is built without IPv6 support; otherwise it is:
11297 local_interfaces = <; ::0 ; 0.0.0.0
11299 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
11303 .section "Overriding local_interfaces and daemon_smtp_ports"
11304 The &%-oX%& command line option can be used to override the values of
11305 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
11306 instance. Another way of doing this would be to use macros and the &%-D%&
11307 option. However, &%-oX%& can be used by any admin user, whereas modification of
11308 the runtime configuration by &%-D%& is allowed only when the caller is root or
11311 The value of &%-oX%& is a list of items. The default colon separator can be
11312 changed in the usual way if required. If there are any items that do not
11313 contain dots or colons (that is, are not IP addresses), the value of
11314 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
11315 items that do contain dots or colons, the value of &%local_interfaces%& is
11316 replaced by those items. Thus, for example,
11320 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
11323 -oX 192.168.34.5.1125
11325 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
11326 (However, since &%local_interfaces%& now contains no items without ports, the
11327 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
11331 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
11332 .cindex "ssmtp protocol"
11333 .cindex "smtps protocol"
11334 .cindex "SMTP" "ssmtp protocol"
11335 .cindex "SMTP" "smtps protocol"
11336 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
11337 before the STARTTLS command was standardized for SMTP. Some legacy clients
11338 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
11339 list of port numbers, connections to those ports must use SSMTP. The most
11340 common use of this option is expected to be
11342 tls_on_connect_ports = 465
11344 because 465 is the usual port number used by the legacy clients. There is also
11345 a command line option &%-tls-on-connect%&, which forces all ports to behave in
11346 this way when a daemon is started.
11348 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
11349 daemon to listen on those ports. You must still specify them in
11350 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
11351 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
11352 connections via the daemon.)
11357 .section "IPv6 address scopes"
11358 .cindex "IPv6" "address scopes"
11359 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
11360 can, in principle, have the same link-local IPv6 address on different
11361 interfaces. Thus, additional information is needed, over and above the IP
11362 address, to distinguish individual interfaces. A convention of using a
11363 percent sign followed by something (often the interface name) has been
11364 adopted in some cases, leading to addresses like this:
11366 fe80::202:b3ff:fe03:45c1%eth0
11368 To accommodate this usage, a percent sign followed by an arbitrary string is
11369 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
11370 to convert a textual IPv6 address for actual use. This function recognizes the
11371 percent convention in operating systems that support it, and it processes the
11372 address appropriately. Unfortunately, some older libraries have problems with
11373 &[getaddrinfo()]&. If
11375 IPV6_USE_INET_PTON=yes
11377 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
11378 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
11379 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
11380 function.) Of course, this means that the additional functionality of
11381 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
11384 .section "Disabling IPv6"
11385 .cindex "IPv6" "disabling"
11386 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
11387 run on a host whose kernel does not support IPv6. The binary will fall back to
11388 using IPv4, but it may waste resources looking up AAAA records, and trying to
11389 connect to IPv6 addresses, causing delays to mail delivery. If you set the
11390 .oindex "&%disable_ipv6%&"
11391 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
11392 activities take place. AAAA records are never looked up, and any IPv6 addresses
11393 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
11394 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
11395 to handle IPv6 literal addresses.
11397 On the other hand, when IPv6 is in use, there may be times when you want to
11398 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
11399 option to globally suppress the lookup of AAAA records for specified domains,
11400 and you can use the &%ignore_target_hosts%& generic router option to ignore
11401 IPv6 addresses in an individual router.
11406 .section "Examples of starting a listening daemon"
11407 The default case in an IPv6 environment is
11409 daemon_smtp_ports = smtp
11410 local_interfaces = <; ::0 ; 0.0.0.0
11412 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
11413 Either one or two sockets may be used, depending on the characteristics of
11414 the TCP/IP stack. (This is complicated and messy; for more information,
11415 read the comments in the &_daemon.c_& source file.)
11417 To specify listening on ports 25 and 26 on all interfaces:
11419 daemon_smtp_ports = 25 : 26
11421 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
11423 local_interfaces = <; ::0.25 ; ::0.26 \
11424 0.0.0.0.25 ; 0.0.0.0.26
11426 To listen on the default port on all IPv4 interfaces, and on port 26 on the
11427 IPv4 loopback address only:
11429 local_interfaces = 0.0.0.0 : 127.0.0.1.26
11431 To specify listening on the default port on specific interfaces only:
11433 local_interfaces = 192.168.34.67 : 192.168.34.67
11435 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
11439 .section "Recognising the local host" "SECTreclocipadd"
11440 The &%local_interfaces%& option is also used when Exim needs to determine
11441 whether or not an IP address refers to the local host. That is, the IP
11442 addresses of all the interfaces on which a daemon is listening are always
11445 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
11446 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
11447 available interfaces from the operating system, and extracts the relevant
11448 (that is, IPv4 or IPv6) addresses to use for checking.
11450 Some systems set up large numbers of virtual interfaces in order to provide
11451 many virtual web servers. In this situation, you may want to listen for
11452 email on only a few of the available interfaces, but nevertheless treat all
11453 interfaces as local when routing. You can do this by setting
11454 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
11455 &"all"& wildcard values. These addresses are recognized as local, but are not
11456 used for listening. Consider this example:
11458 local_interfaces = <; 127.0.0.1 ; ::1 ; \
11460 3ffe:2101:12:1:a00:20ff:fe86:a061
11462 extra_local_interfaces = <; ::0 ; 0.0.0.0
11464 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
11465 address, but all available interface addresses are treated as local when
11468 In some environments the local host name may be in an MX list, but with an IP
11469 address that is not assigned to any local interface. In other cases it may be
11470 desirable to treat other host names as if they referred to the local host. Both
11471 these cases can be handled by setting the &%hosts_treat_as_local%& option.
11472 This contains host names rather than IP addresses. When a host is referenced
11473 during routing, either via an MX record or directly, it is treated as the local
11474 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
11475 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
11479 .section "Delivering to a remote host"
11480 Delivery to a remote host is handled by the smtp transport. By default, it
11481 allows the system's TCP/IP functions to choose which interface to use (if
11482 there is more than one) when connecting to a remote host. However, the
11483 &%interface%& option can be set to specify which interface is used. See the
11484 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
11490 . ////////////////////////////////////////////////////////////////////////////
11491 . ////////////////////////////////////////////////////////////////////////////
11493 .chapter "Main configuration" "CHAPmainconfig"
11494 .scindex IIDconfima "configuration file" "main section"
11495 .scindex IIDmaiconf "main configuration"
11496 The first part of the run time configuration file contains three types of item:
11499 Macro definitions: These lines start with an upper case letter. See section
11500 &<<SECTmacrodefs>>& for details of macro processing.
11502 Named list definitions: These lines start with one of the words &"domainlist"&,
11503 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
11504 section &<<SECTnamedlists>>&.
11506 Main configuration settings: Each setting occupies one line of the file
11507 (with possible continuations). If any setting is preceded by the word
11508 &"hide"&, the &%-bP%& command line option displays its value to admin users
11509 only. See section &<<SECTcos>>& for a description of the syntax of these option
11513 This chapter specifies all the main configuration options, along with their
11514 types and default values. For ease of finding a particular option, they appear
11515 in alphabetical order in section &<<SECTalomo>>& below. However, because there
11516 are now so many options, they are first listed briefly in functional groups, as
11517 an aid to finding the name of the option you are looking for. Some options are
11518 listed in more than one group.
11520 .section "Miscellaneous"
11522 .row &%bi_command%& "to run for &%-bi%& command line option"
11523 .row &%disable_ipv6%& "do no IPv6 processing"
11524 .row &%keep_malformed%& "for broken files &-- should not happen"
11525 .row &%localhost_number%& "for unique message ids in clusters"
11526 .row &%message_body_visible%& "how much to show in &$message_body$&"
11527 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
11528 .row &%print_topbitchars%& "top-bit characters are printing"
11529 .row &%timezone%& "force time zone"
11533 .section "Exim parameters"
11535 .row &%exim_group%& "override compiled-in value"
11536 .row &%exim_path%& "override compiled-in value"
11537 .row &%exim_user%& "override compiled-in value"
11538 .row &%primary_hostname%& "default from &[uname()]&"
11539 .row &%split_spool_directory%& "use multiple directories"
11540 .row &%spool_directory%& "override compiled-in value"
11545 .section "Privilege controls"
11547 .row &%admin_groups%& "groups that are Exim admin users"
11548 .row &%deliver_drop_privilege%& "drop root for delivery processes"
11549 .row &%local_from_check%& "insert &'Sender:'& if necessary"
11550 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
11551 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
11552 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
11553 .row &%never_users%& "do not run deliveries as these"
11554 .row &%prod_requires_admin%& "forced delivery requires admin user"
11555 .row &%queue_list_requires_admin%& "queue listing requires admin user"
11556 .row &%trusted_groups%& "groups that are trusted"
11557 .row &%trusted_users%& "users that are trusted"
11564 .row &%hosts_connection_nolog%& "exemption from connect logging"
11565 .row &%log_file_path%& "override compiled-in value"
11566 .row &%log_selector%& "set/unset optional logging"
11567 .row &%log_timezone%& "add timezone to log lines"
11568 .row &%message_logs%& "create per-message logs"
11569 .row &%preserve_message_logs%& "after message completion"
11570 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
11571 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
11572 .row &%syslog_facility%& "set syslog &""facility""& field"
11573 .row &%syslog_processname%& "set syslog &""ident""& field"
11574 .row &%syslog_timestamp%& "timestamp syslog lines"
11575 .row &%write_rejectlog%& "control use of message log"
11580 .section "Frozen messages"
11582 .row &%auto_thaw%& "sets time for retrying frozen messages"
11583 .row &%freeze_tell%& "send message when freezing"
11584 .row &%move_frozen_messages%& "to another directory"
11585 .row &%timeout_frozen_after%& "keep frozen messages only so long"
11590 .section "Data lookups"
11592 .row &%ldap_default_servers%& "used if no server in query"
11593 .row &%ldap_version%& "set protocol version"
11594 .row &%lookup_open_max%& "lookup files held open"
11595 .row &%mysql_servers%& "as it says"
11596 .row &%oracle_servers%& "as it says"
11597 .row &%pgsql_servers%& "as it says"
11598 .row &%sqlite_lock_timeout%& "as it says"
11603 .section "Message ids"
11605 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
11606 .row &%message_id_header_text%& "ditto"
11611 .section "Embedded Perl Startup"
11613 .row &%perl_at_start%& "always start the interpreter"
11614 .row &%perl_startup%& "code to obey when starting Perl"
11621 .row &%daemon_smtp_ports%& "default ports"
11622 .row &%daemon_startup_retries%& "number of times to retry"
11623 .row &%daemon_startup_sleep%& "time to sleep between tries"
11624 .row &%extra_local_interfaces%& "not necessarily listened on"
11625 .row &%local_interfaces%& "on which to listen, with optional ports"
11626 .row &%pid_file_path%& "override compiled-in value"
11627 .row &%queue_run_max%& "maximum simultaneous queue runners"
11632 .section "Resource control"
11634 .row &%check_log_inodes%& "before accepting a message"
11635 .row &%check_log_space%& "before accepting a message"
11636 .row &%check_spool_inodes%& "before accepting a message"
11637 .row &%check_spool_space%& "before accepting a message"
11638 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
11639 .row &%queue_only_load%& "queue incoming if load high"
11640 .row &%queue_run_max%& "maximum simultaneous queue runners"
11641 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
11642 .row &%smtp_accept_max%& "simultaneous incoming connections"
11643 .row &%smtp_accept_max_nommail%& "non-mail commands"
11644 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
11645 .row &%smtp_accept_max_per_connection%& "messages per connection"
11646 .row &%smtp_accept_max_per_host%& "connections from one host"
11647 .row &%smtp_accept_queue%& "queue mail if more connections"
11648 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
11650 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
11651 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
11652 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
11653 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
11654 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
11659 .section "Policy controls"
11661 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
11662 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
11663 .row &%acl_smtp_auth%& "ACL for AUTH"
11664 .row &%acl_smtp_connect%& "ACL for connection"
11665 .row &%acl_smtp_data%& "ACL for DATA"
11666 .row &%acl_smtp_etrn%& "ACL for ETRN"
11667 .row &%acl_smtp_expn%& "ACL for EXPN"
11668 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
11669 .row &%acl_smtp_mail%& "ACL for MAIL"
11670 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
11671 .row &%acl_smtp_mime%& "ACL for MIME parts"
11672 .row &%acl_smtp_predata%& "ACL for start of data"
11673 .row &%acl_smtp_quit%& "ACL for QUIT"
11674 .row &%acl_smtp_rcpt%& "ACL for RCPT"
11675 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
11676 .row &%acl_smtp_vrfy%& "ACL for VRFY"
11677 .row &%av_scanner%& "specify virus scanner"
11678 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
11680 .row &%dns_csa_search_limit%& "control CSA parent search depth"
11681 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
11682 .row &%header_maxsize%& "total size of message header"
11683 .row &%header_line_maxsize%& "individual header line limit"
11684 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
11685 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
11686 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
11687 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
11688 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
11689 .row &%host_lookup%& "host name looked up for these hosts"
11690 .row &%host_lookup_order%& "order of DNS and local name lookups"
11691 .row &%host_reject_connection%& "reject connection from these hosts"
11692 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
11693 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
11694 .row &%message_size_limit%& "for all messages"
11695 .row &%percent_hack_domains%& "recognize %-hack for these domains"
11696 .row &%spamd_address%& "set interface to SpamAssassin"
11701 .section "Callout cache"
11703 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
11705 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
11707 .row &%callout_negative_expire%& "timeout for negative address cache item"
11708 .row &%callout_positive_expire%& "timeout for positive address cache item"
11709 .row &%callout_random_local_part%& "string to use for &""random""& testing"
11716 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
11717 .row &%tls_certificate%& "location of server certificate"
11718 .row &%tls_crl%& "certificate revocation list"
11719 .row &%tls_dhparam%& "DH parameters for server"
11720 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
11721 .row &%tls_privatekey%& "location of server private key"
11722 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
11723 .row &%tls_require_ciphers%& "specify acceptable cipers"
11724 .row &%tls_try_verify_hosts%& "try to verify client certificate"
11725 .row &%tls_verify_certificates%& "expected client certificates"
11726 .row &%tls_verify_hosts%& "insist on client certificate verify"
11731 .section "Local user handling"
11733 .row &%finduser_retries%& "useful in NIS environments"
11734 .row &%gecos_name%& "used when creating &'Sender:'&"
11735 .row &%gecos_pattern%& "ditto"
11736 .row &%max_username_length%& "for systems that truncate"
11737 .row &%unknown_login%& "used when no login name found"
11738 .row &%unknown_username%& "ditto"
11739 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
11740 .row &%uucp_from_sender%& "ditto"
11745 .section "All incoming messages (SMTP and non-SMTP)"
11747 .row &%header_maxsize%& "total size of message header"
11748 .row &%header_line_maxsize%& "individual header line limit"
11749 .row &%message_size_limit%& "applies to all messages"
11750 .row &%percent_hack_domains%& "recognize %-hack for these domains"
11751 .row &%received_header_text%& "expanded to make &'Received:'&"
11752 .row &%received_headers_max%& "for mail loop detection"
11753 .row &%recipients_max%& "limit per message"
11754 .row &%recipients_max_reject%& "permanently reject excess"
11760 .section "Non-SMTP incoming messages"
11762 .row &%receive_timeout%& "for non-SMTP messages"
11769 .section "Incoming SMTP messages"
11770 See also the &'Policy controls'& section above.
11773 .row &%host_lookup%& "host name looked up for these hosts"
11774 .row &%host_lookup_order%& "order of DNS and local name lookups"
11775 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
11776 .row &%rfc1413_hosts%& "make ident calls to these hosts"
11777 .row &%rfc1413_query_timeout%& "zero disables ident calls"
11778 .row &%sender_unqualified_hosts%& "may send unqualified senders"
11779 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
11780 .row &%smtp_accept_max%& "simultaneous incoming connections"
11781 .row &%smtp_accept_max_nonmail%& "non-mail commands"
11782 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
11783 .row &%smtp_accept_max_per_connection%& "messages per connection"
11784 .row &%smtp_accept_max_per_host%& "connections from one host"
11785 .row &%smtp_accept_queue%& "queue mail if more connections"
11786 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
11788 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
11789 .row &%smtp_active_hostname%& "host name to use in messages"
11790 .row &%smtp_banner%& "text for welcome banner"
11791 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
11792 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
11793 .row &%smtp_enforce_sync%& "of SMTP command/responses"
11794 .row &%smtp_etrn_command%& "what to run for ETRN"
11795 .row &%smtp_etrn_serialize%& "only one at once"
11796 .row &%smtp_load_reserve%& "only reserve hosts if this load"
11797 .row &%smtp_max_unknown_commands%& "before dropping connection"
11798 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
11799 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
11800 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
11801 .row &%smtp_receive_timeout%& "per command or data line"
11802 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
11803 .row &%smtp_return_error_details%& "give detail on rejections"
11808 .section "SMTP extensions"
11810 .row &%accept_8bitmime%& "advertise 8BITMIME"
11811 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
11812 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
11813 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
11814 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
11815 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
11820 .section "Processing messages"
11822 .row &%allow_domain_literals%& "recognize domain literal syntax"
11823 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
11824 .row &%allow_utf8_domains%& "in addresses"
11825 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
11827 .row &%delivery_date_remove%& "from incoming messages"
11828 .row &%envelope_to_remote%& "from incoming messages"
11829 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
11830 .row &%headers_charset%& "default for translations"
11831 .row &%qualify_domain%& "default for senders"
11832 .row &%qualify_recipient%& "default for recipients"
11833 .row &%return_path_remove%& "from incoming messages"
11834 .row &%strip_excess_angle_brackets%& "in addresses"
11835 .row &%strip_trailing_dot%& "at end of addresses"
11836 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
11841 .section "System filter"
11843 .row &%system_filter%& "locate system filter"
11844 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
11846 .row &%system_filter_file_transport%& "transport for delivery to a file"
11847 .row &%system_filter_group%& "group for filter running"
11848 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
11849 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
11850 .row &%system_filter_user%& "user for filter running"
11855 .section "Routing and delivery"
11857 .row &%disable_ipv6%& "do no IPv6 processing"
11858 .row &%dns_again_means_nonexist%& "for broken domains"
11859 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
11860 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
11861 .row &%dns_retrans%& "parameter for resolver"
11862 .row &%dns_retry%& "parameter for resolver"
11863 .row &%hold_domains%& "hold delivery for these domains"
11864 .row &%local_interfaces%& "for routing checks"
11865 .row &%queue_domains%& "no immediate delivery for these"
11866 .row &%queue_only%& "no immediate delivery at all"
11867 .row &%queue_only_file%& "no immediate delivery if file exists"
11868 .row &%queue_only_load%& "no immediate delivery if load is high"
11869 .row &%queue_only_override%& "allow command line to override"
11870 .row &%queue_run_in_order%& "order of arrival"
11871 .row &%queue_run_max%& "of simultaneous queue runners"
11872 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
11873 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
11874 .row &%remote_sort_domains%& "order of remote deliveries"
11875 .row &%retry_data_expire%& "timeout for retry data"
11876 .row &%retry_interval_max%& "safety net for retry rules"
11881 .section "Bounce and warning messages"
11883 .row &%bounce_message_file%& "content of bounce"
11884 .row &%bounce_message_text%& "content of bounce"
11885 .row &%bounce_return_body%& "include body if returning message"
11886 .row &%bounce_return_message%& "include original message in bounce"
11887 .row &%bounce_return_size_limit%& "limit on returned message"
11888 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
11889 .row &%errors_copy%& "copy bounce messages"
11890 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
11891 .row &%delay_warning%& "time schedule"
11892 .row &%delay_warning_condition%& "condition for warning messages"
11893 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
11894 .row &%smtp_return_error_details%& "give detail on rejections"
11895 .row &%warn_message_file%& "content of warning message"
11900 .section "Alphabetical list of main options" "SECTalomo"
11901 Those options that undergo string expansion before use are marked with
11904 .option accept_8bitmime main boolean false
11906 .cindex "8-bit characters"
11907 This option causes Exim to send 8BITMIME in its response to an SMTP
11908 EHLO command, and to accept the BODY= parameter on MAIL commands.
11909 However, though Exim is 8-bit clean, it is not a protocol converter, and it
11910 takes no steps to do anything special with messages received by this route.
11911 Consequently, this option is turned off by default.
11913 .option acl_not_smtp main string&!! unset
11914 .cindex "&ACL;" "for non-SMTP messages"
11915 .cindex "non-SMTP messages" "ACLs for"
11916 This option defines the ACL that is run when a non-SMTP message is on the point
11917 of being accepted. See chapter &<<CHAPACL>>& for further details.
11919 .option acl_not_smtp_mime main string&!! unset
11920 This option defines the ACL that is run for individual MIME parts of non-SMTP
11921 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
11924 .option acl_smtp_auth main string&!! unset
11925 .cindex "&ACL;" "setting up for SMTP commands"
11926 .cindex "AUTH" "ACL for"
11927 This option defines the ACL that is run when an SMTP AUTH command is
11928 received. See chapter &<<CHAPACL>>& for further details.
11930 .option acl_smtp_connect main string&!! unset
11931 .cindex "&ACL;" "on SMTP connection"
11932 This option defines the ACL that is run when an SMTP connection is received.
11933 See chapter &<<CHAPACL>>& for further details.
11935 .option acl_smtp_data main string&!! unset
11936 .cindex "DATA" "ACL for"
11937 This option defines the ACL that is run after an SMTP DATA command has been
11938 processed and the message itself has been received, but before the final
11939 acknowledgement is sent. See chapter &<<CHAPACL>>& for further details.
11941 .option acl_smtp_etrn main string&!! unset
11942 .cindex "ETRN" "ACL for"
11943 This option defines the ACL that is run when an SMTP ETRN command is
11944 received. See chapter &<<CHAPACL>>& for further details.
11946 .option acl_smtp_expn main string&!! unset
11947 .cindex "EXPN" "ACL for"
11948 This option defines the ACL that is run when an SMTP EXPN command is
11949 received. See chapter &<<CHAPACL>>& for further details.
11951 .option acl_smtp_helo main string&!! unset
11952 .cindex "EHLO" "ACL for"
11953 .cindex "HELO" "ACL for"
11954 This option defines the ACL that is run when an SMTP EHLO or HELO
11955 command is received. See chapter &<<CHAPACL>>& for further details.
11958 .option acl_smtp_mail main string&!! unset
11959 .cindex "MAIL" "ACL for"
11960 This option defines the ACL that is run when an SMTP MAIL command is
11961 received. See chapter &<<CHAPACL>>& for further details.
11963 .option acl_smtp_mailauth main string&!! unset
11964 .cindex "AUTH" "on MAIL command"
11965 This option defines the ACL that is run when there is an AUTH parameter on
11966 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
11967 &<<CHAPSMTPAUTH>>& for details of authentication.
11969 .option acl_smtp_mime main string&!! unset
11970 .cindex "MIME content scanning" "ACL for"
11971 This option is available when Exim is built with the content-scanning
11972 extension. It defines the ACL that is run for each MIME part in a message. See
11973 section &<<SECTscanmimepart>>& for details.
11975 .option acl_smtp_predata main string&!! unset
11976 This option defines the ACL that is run when an SMTP DATA command is
11977 received, before the message itself is received. See chapter &<<CHAPACL>>& for
11980 .option acl_smtp_quit main string&!! unset
11981 .cindex "QUIT" "ACL for"
11982 This option defines the ACL that is run when an SMTP QUIT command is
11983 received. See chapter &<<CHAPACL>>& for further details.
11985 .option acl_smtp_rcpt main string&!! unset
11986 .cindex "RCPT" "ACL for"
11987 This option defines the ACL that is run when an SMTP RCPT command is
11988 received. See chapter &<<CHAPACL>>& for further details.
11990 .option acl_smtp_starttls main string&!! unset
11991 .cindex "STARTTLS" "ACL for"
11992 This option defines the ACL that is run when an SMTP STARTTLS command is
11993 received. See chapter &<<CHAPACL>>& for further details.
11995 .option acl_smtp_vrfy main string&!! unset
11996 .cindex "VRFY" "ACL for"
11997 This option defines the ACL that is run when an SMTP VRFY command is
11998 received. See chapter &<<CHAPACL>>& for further details.
12000 .option admin_groups main "string list&!!" unset
12001 .cindex "admin user"
12002 This option is expanded just once, at the start of Exim's processing. If the
12003 current group or any of the supplementary groups of an Exim caller is in this
12004 colon-separated list, the caller has admin privileges. If all your system
12005 programmers are in a specific group, for example, you can give them all Exim
12006 admin privileges by putting that group in &%admin_groups%&. However, this does
12007 not permit them to read Exim's spool files (whose group owner is the Exim gid).
12008 To permit this, you have to add individuals to the Exim group.
12010 .option allow_domain_literals main boolean false
12011 .cindex "domain literal"
12012 If this option is set, the RFC 2822 domain literal format is permitted in
12013 email addresses. The option is not set by default, because the domain literal
12014 format is not normally required these days, and few people know about it. It
12015 has, however, been exploited by mail abusers.
12017 Unfortunately, it seems that some DNS black list maintainers are using this
12018 format to report black listing to postmasters. If you want to accept messages
12019 addressed to your hosts by IP address, you need to set
12020 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
12021 domains (defined in the named domain list &%local_domains%& in the default
12022 configuration). This &"magic string"& matches the domain literal form of all
12023 the local host's IP addresses.
12026 .option allow_mx_to_ip main boolean false
12027 .cindex "MX record" "pointing to IP address"
12028 It appears that more and more DNS zone administrators are breaking the rules
12029 and putting domain names that look like IP addresses on the right hand side of
12030 MX records. Exim follows the rules and rejects this, giving an error message
12031 that explains the mis-configuration. However, some other MTAs support this
12032 practice, so to avoid &"Why can't Exim do this?"& complaints,
12033 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
12034 recommended, except when you have no other choice.
12036 .option allow_utf8_domains main boolean false
12037 .cindex "domain" "UTF-8 characters in"
12038 .cindex "UTF-8" "in domain name"
12039 Lots of discussion is going on about internationalized domain names. One
12040 camp is strongly in favour of just using UTF-8 characters, and it seems
12041 that at least two other MTAs permit this. This option allows Exim users to
12042 experiment if they wish.
12044 If it is set true, Exim's domain parsing function allows valid
12045 UTF-8 multicharacters to appear in domain name components, in addition to
12046 letters, digits, and hyphens. However, just setting this option is not
12047 enough; if you want to look up these domain names in the DNS, you must also
12048 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
12049 suitable setting is:
12051 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
12052 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
12054 Alternatively, you can just disable this feature by setting
12056 dns_check_names_pattern =
12058 That is, set the option to an empty string so that no check is done.
12061 .option auth_advertise_hosts main "host list&!!" *
12062 .cindex "authentication" "advertising"
12063 .cindex "AUTH" "advertising"
12064 If any server authentication mechanisms are configured, Exim advertises them in
12065 response to an EHLO command only if the calling host matches this list.
12066 Otherwise, Exim does not advertise AUTH.
12067 Exim does not accept AUTH commands from clients to which it has not
12068 advertised the availability of AUTH. The advertising of individual
12069 authentication mechanisms can be controlled by the use of the
12070 &%server_advertise_condition%& generic authenticator option on the individual
12071 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
12073 Certain mail clients (for example, Netscape) require the user to provide a name
12074 and password for authentication if AUTH is advertised, even though it may
12075 not be needed (the host may accept messages from hosts on its local LAN without
12076 authentication, for example). The &%auth_advertise_hosts%& option can be used
12077 to make these clients more friendly by excluding them from the set of hosts to
12078 which Exim advertises AUTH.
12080 .cindex "AUTH" "advertising when encrypted"
12081 If you want to advertise the availability of AUTH only when the connection
12082 is encrypted using TLS, you can make use of the fact that the value of this
12083 option is expanded, with a setting like this:
12085 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
12087 .cindex "&$tls_cipher$&"
12088 If &$tls_cipher$& is empty, the session is not encrypted, and the result of
12089 the expansion is empty, thus matching no hosts. Otherwise, the result of the
12090 expansion is *, which matches all hosts.
12093 .option auto_thaw main time 0s
12094 .cindex "thawing messages"
12095 .cindex "unfreezing messages"
12096 If this option is set to a time greater than zero, a queue runner will try a
12097 new delivery attempt on any frozen message, other than a bounce message, if
12098 this much time has passed since it was frozen. This may result in the message
12099 being re-frozen if nothing has changed since the last attempt. It is a way of
12100 saying &"keep on trying, even though there are big problems"&.
12102 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
12103 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
12104 thought to be very useful any more, and its use should probably be avoided.
12106 .option av_scanner main string "see below"
12107 This option is available if Exim is built with the content-scanning extension.
12108 It specifies which anti-virus scanner to use. The default value is:
12110 sophie:/var/run/sophie
12112 If the value of &%av_scanner%& starts with dollar character, it is expanded
12113 before use. See section &<<SECTscanvirus>>& for further details.
12117 .option bi_command main string unset
12118 .cindex "&%-bi%& option"
12119 This option supplies the name of a command that is run when Exim is called with
12120 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
12121 just the command name, it is not a complete command line. If an argument is
12122 required, it must come from the &%-oA%& command line option.
12125 .option bounce_message_file main string unset
12126 .cindex "bounce message" "customizing"
12127 .cindex "customizing" "bounce message"
12128 This option defines a template file containing paragraphs of text to be used
12129 for constructing bounce messages. Details of the file's contents are given in
12130 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
12133 .option bounce_message_text main string unset
12134 When this option is set, its contents are included in the default bounce
12135 message immediately after &"This message was created automatically by mail
12136 delivery software."& It is not used if &%bounce_message_file%& is set.
12138 .option bounce_return_body main boolean true
12139 .cindex "bounce message" "including body"
12141 This option controls whether the body of an incoming message is included in a
12142 bounce message when &%bounce_return_message%& is true. The default setting
12143 causes the entire message, both header and body, to be returned (subject to the
12144 value of &%bounce_return_size_limit%&). If this option is false, only the
12145 message header is included. In the case of a non-SMTP message containing an
12146 error that is detected during reception, only those header lines preceding the
12147 point at which the error was detected are returned.
12148 .cindex "bounce message" "including original"
12151 .option bounce_return_message main boolean true
12153 If this option is set false, none of the original message is included in
12154 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
12155 &%bounce_return_body%&.
12159 .option bounce_return_size_limit main integer 100K
12160 .cindex "size limit" "of bounce"
12161 .cindex "bounce message" "size limit"
12162 .cindex "limit" "bounce message size"
12163 This option sets a limit in bytes on the size of messages that are returned to
12164 senders as part of bounce messages when &%bounce_return_message%& is true. The
12165 limit should be less than the value of the global &%message_size_limit%& and of
12166 any &%message_size_limit%& settings on transports, to allow for the bounce text
12167 that Exim generates. If this option is set to zero there is no limit.
12169 When the body of any message that is to be included in a bounce message is
12170 greater than the limit, it is truncated, and a comment pointing this out is
12171 added at the top. The actual cutoff may be greater than the value given, owing
12172 to the use of buffering for transferring the message in chunks (typically 8K in
12173 size). The idea is to save bandwidth on those undeliverable 15-megabyte
12176 .option bounce_sender_authentication main string unset
12177 .cindex "bounce message" "sender authentication"
12178 .cindex "authentication" "bounce message"
12179 .cindex "AUTH" "on bounce message"
12180 This option provides an authenticated sender address that is sent with any
12181 bounce messages generated by Exim that are sent over an authenticated SMTP
12182 connection. A typical setting might be:
12184 bounce_sender_authentication = mailer-daemon@my.domain.example
12186 which would cause bounce messages to be sent using the SMTP command:
12188 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
12190 The value of &%bounce_sender_authentication%& must always be a complete email
12193 .option callout_domain_negative_expire main time 3h
12194 .cindex "caching" "callout timeouts"
12195 .cindex "callout" "caching timeouts"
12196 This option specifies the expiry time for negative callout cache data for a
12197 domain. See section &<<SECTcallver>>& for details of callout verification, and
12198 section &<<SECTcallvercache>>& for details of the caching.
12201 .option callout_domain_positive_expire main time 7d
12202 This option specifies the expiry time for positive callout cache data for a
12203 domain. See section &<<SECTcallver>>& for details of callout verification, and
12204 section &<<SECTcallvercache>>& for details of the caching.
12207 .option callout_negative_expire main time 2h
12208 This option specifies the expiry time for negative callout cache data for an
12209 address. See section &<<SECTcallver>>& for details of callout verification, and
12210 section &<<SECTcallvercache>>& for details of the caching.
12213 .option callout_positive_expire main time 24h
12214 This option specifies the expiry time for positive callout cache data for an
12215 address. See section &<<SECTcallver>>& for details of callout verification, and
12216 section &<<SECTcallvercache>>& for details of the caching.
12219 .option callout_random_local_part main string&!! "see below"
12220 This option defines the &"random"& local part that can be used as part of
12221 callout verification. The default value is
12223 $primary_host_name-$tod_epoch-testing
12225 See section &<<CALLaddparcall>>& for details of how this value is used.
12228 .option check_log_inodes main integer 0
12229 See &%check_spool_space%& below.
12232 .option check_log_space main integer 0
12233 See &%check_spool_space%& below.
12235 .oindex "&%check_rfc2047_length%&"
12236 .cindex "RFC 2047" "disabling length check"
12237 .option check_rfc2047_length " User: main" boolean true
12238 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
12239 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
12240 word; strings to be encoded that exceed this length are supposed to use
12241 multiple encoded words. By default, Exim does not recognize encoded words that
12242 exceed the maximum length. However, it seems that some software, in violation
12243 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
12244 set false, Exim recognizes encoded words of any length.
12247 .option check_spool_inodes main integer 0
12248 See &%check_spool_space%& below.
12251 .option check_spool_space main integer 0
12252 .cindex "checking disk space"
12253 .cindex "disk space" "checking"
12254 .cindex "spool directory" "checking space"
12255 The four &%check_...%& options allow for checking of disk resources before a
12256 message is accepted.
12258 .cindex "&$log_inodes$&"
12259 .cindex "&$log_space$&"
12260 .cindex "&$spool_inodes$&"
12261 .cindex "&$spool_space$&"
12262 When any of these options are set, they apply to all incoming messages. If you
12263 want to apply different checks to different kinds of message, you can do so by
12264 testing the the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
12265 &$spool_space$& in an ACL with appropriate additional conditions.
12268 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
12269 either value is greater than zero, for example:
12271 check_spool_space = 10M
12272 check_spool_inodes = 100
12274 The spool partition is the one that contains the directory defined by
12275 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
12278 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
12279 files are written if either is greater than zero. These should be set only if
12280 &%log_file_path%& and &%spool_directory%& refer to different partitions.
12282 If there is less space or fewer inodes than requested, Exim refuses to accept
12283 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
12284 error response to the MAIL command. If ESMTP is in use and there was a
12285 SIZE parameter on the MAIL command, its value is added to the
12286 &%check_spool_space%& value, and the check is performed even if
12287 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
12289 The values for &%check_spool_space%& and &%check_log_space%& are held as a
12290 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
12292 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
12293 failure a message is written to stderr and Exim exits with a non-zero code, as
12294 it obviously cannot send an error message of any kind.
12296 .option daemon_smtp_ports main string &`smtp`&
12297 .cindex "port" "for daemon"
12298 .cindex "TCP/IP" "setting listening ports"
12299 This option specifies one or more default SMTP ports on which the Exim daemon
12300 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
12301 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
12303 .option daemon_startup_retries main integer 9
12304 .cindex "daemon startup" "retrying"
12305 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
12306 the daemon at startup when it cannot immediately bind a listening socket
12307 (typically because the socket is already in use): &%daemon_startup_retries%&
12308 defines the number of retries after the first failure, and
12309 &%daemon_startup_sleep%& defines the length of time to wait between retries.
12311 .option daemon_startup_sleep main time 30s
12312 See &%daemon_startup_retries%&.
12314 .option delay_warning main "time list" 24h
12315 .cindex "warning of delay"
12316 .cindex "delay warning" "specifying"
12317 When a message is delayed, Exim sends a warning message to the sender at
12318 intervals specified by this option. The data is a colon-separated list of times
12319 after which to send warning messages. If the value of the option is an empty
12320 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
12321 message has been on the queue for longer than the last time, the last interval
12322 between the times is used to compute subsequent warning times. For example,
12325 delay_warning = 4h:8h:24h
12327 the first message is sent after 4 hours, the second after 8 hours, and
12328 the third one after 24 hours. After that, messages are sent every 16 hours,
12329 because that is the interval between the last two times on the list. If you set
12330 just one time, it specifies the repeat interval. For example, with:
12334 messages are repeated every six hours. To stop warnings after a given time, set
12335 a very large time at the end of the list. For example:
12337 delay_warning = 2h:12h:99d
12340 .option delay_warning_condition main string&!! "see below"
12341 .cindex "&$domain$&"
12342 The string is expanded at the time a warning message might be sent. If all the
12343 deferred addresses have the same domain, it is set in &$domain$& during the
12344 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
12345 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
12346 &"false"& (the comparison being done caselessly) then the warning message is
12347 not sent. The default is
12349 delay_warning_condition = \
12350 ${if match{$h_precedence:}{(?i)bulk|list|junk}{no}{yes}}
12352 which suppresses the sending of warnings about messages that have &"bulk"&,
12353 &"list"& or &"junk"& in a &'Precedence:'& header.
12355 .option deliver_drop_privilege main boolean false
12356 .cindex "unprivileged delivery"
12357 .cindex "delivery" "unprivileged"
12358 If this option is set true, Exim drops its root privilege at the start of a
12359 delivery process, and runs as the Exim user throughout. This severely restricts
12360 the kinds of local delivery that are possible, but is viable in certain types
12361 of configuration. There is a discussion about the use of root privilege in
12362 chapter &<<CHAPsecurity>>&.
12364 .option deliver_queue_load_max main fixed-point unset
12365 .cindex "load average"
12366 .cindex "queue runner" "abandoning"
12367 When this option is set, a queue run is abandoned if the system load average
12368 becomes greater than the value of the option. The option has no effect on
12369 ancient operating systems on which Exim cannot determine the load average.
12370 See also &%queue_only_load%& and &%smtp_load_reserve%&.
12373 .option delivery_date_remove main boolean true
12374 .cindex "&'Delivery-date:'& header line"
12375 Exim's transports have an option for adding a &'Delivery-date:'& header to a
12376 message when it is delivered, in exactly the same way as &'Return-path:'& is
12377 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
12378 should not be present in incoming messages, and this option causes them to be
12379 removed at the time the message is received, to avoid any problems that might
12380 occur when a delivered message is subsequently sent on to some other recipient.
12384 .option disable_ipv6 main boolean false
12385 .cindex "IPv6" "disabling"
12386 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
12387 activities take place. AAAA records are never looked up, and any IPv6 addresses
12388 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
12389 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12390 to handle IPv6 literal addresses.
12394 .option dns_again_means_nonexist main "domain list&!!" unset
12395 .cindex "DNS" "&""try again""& response; overriding"
12396 DNS lookups give a &"try again"& response for the DNS errors
12397 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
12398 keep trying to deliver a message, or to give repeated temporary errors to
12399 incoming mail. Sometimes the effect is caused by a badly set up name server and
12400 may persist for a long time. If a domain which exhibits this problem matches
12401 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
12402 This option should be used with care. You can make it apply to reverse lookups
12403 by a setting such as this:
12405 dns_again_means_nonexist = *.in-addr.arpa
12408 This option applies to all DNS lookups that Exim does. It also applies when the
12409 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
12410 since these are most likely to be caused by DNS lookup problems. The
12411 &(dnslookup)& router has some options of its own for controlling what happens
12412 when lookups for MX or SRV records give temporary errors. These more specific
12413 options are applied after this global option.
12416 .option dns_check_names_pattern main string "see below"
12417 .cindex "DNS" "pre-check of name syntax"
12419 When this option is set to a non-empty string, it causes Exim to check domain
12420 names for characters that are not allowed in host names before handing them to
12421 the DNS resolver, because some resolvers give temporary errors for names that
12422 contain unusual characters. If a domain name contains any unwanted characters,
12423 a &"not found"& result is forced, and the resolver is not called. The check is
12424 done by matching the domain name against a regular expression, which is the
12425 value of this option. The default pattern is
12427 dns_check_names_pattern = \
12428 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
12430 which permits only letters, digits, slashes, and hyphens in components, but
12431 they must start and end with a letter or digit. Hyphens are not, in fact,
12432 permitted in host names, but they are found in certain NS records (which can be
12433 accessed in Exim by using a &%dnsdb%& lookup). If you set
12434 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
12438 .option dns_csa_search_limit main integer 5
12439 This option controls the depth of parental searching for CSA SRV records in the
12440 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
12442 .option dns_csa_use_reverse main boolean true
12443 This option controls whether or not an IP address, given as a CSA domain, is
12444 reversed and looked up in the reverse DNS, as described in more detail in
12445 section &<<SECTverifyCSA>>&.
12447 .option dns_ipv4_lookup main "domain list&!!" unset
12448 .cindex "IPv6" "DNS lookup for AAAA records"
12449 .cindex "DNS" "IPv6 lookup for AAAA records"
12451 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
12452 looks for IPv6 address records (AAAA records) as well as IPv4 address records
12453 (A records) when trying to find IP addresses for hosts, unless the host's
12454 domain matches this list.
12456 This is a fudge to help with name servers that give big delays or otherwise do
12457 not work for the AAAA record type. In due course, when the world's name
12458 servers have all been upgraded, there should be no need for this option.
12462 .option dns_retrans main time 0s
12463 .cindex "DNS" "resolver options"
12464 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
12465 retransmission and retry parameters for DNS lookups. Values of zero (the
12466 defaults) leave the system default settings unchanged. The first value is the
12467 time between retries, and the second is the number of retries. It isn't
12468 totally clear exactly how these settings affect the total time a DNS lookup may
12469 take. I haven't found any documentation about timeouts on DNS lookups; these
12470 parameter values are available in the external resolver interface structure,
12471 but nowhere does it seem to describe how they are used or what you might want
12475 .option dns_retry main integer 0
12476 See &%dns_retrans%& above.
12479 .option drop_cr main boolean false
12480 This is an obsolete option that is now a no-op. It used to affect the way Exim
12481 handled CR and LF characters in incoming messages. What happens now is
12482 described in section &<<SECTlineendings>>&.
12485 .option envelope_to_remove main boolean true
12486 .cindex "&'Envelope-to:'& header line"
12487 Exim's transports have an option for adding an &'Envelope-to:'& header to a
12488 message when it is delivered, in exactly the same way as &'Return-path:'& is
12489 handled. &'Envelope-to:'& records the original recipient address from the
12490 messages's envelope that caused the delivery to happen. Such headers should not
12491 be present in incoming messages, and this option causes them to be removed at
12492 the time the message is received, to avoid any problems that might occur when a
12493 delivered message is subsequently sent on to some other recipient.
12496 .option errors_copy main "string list&!!" unset
12497 .cindex "bounce message" "copy to other address"
12498 .cindex "copy of bounce message"
12499 Setting this option causes Exim to send bcc copies of bounce messages that it
12500 generates to other addresses. &*Note*&: This does not apply to bounce messages
12501 coming from elsewhere. The value of the option is a colon-separated list of
12502 items. Each item consists of a pattern, terminated by white space, followed by
12503 a comma-separated list of email addresses. If a pattern contains spaces, it
12504 must be enclosed in double quotes.
12506 Each pattern is processed in the same way as a single item in an address list
12507 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
12508 the bounce message, the message is copied to the addresses on the list. The
12509 items are scanned in order, and once a matching one is found, no further items
12510 are examined. For example:
12512 errors_copy = spqr@mydomain postmaster@mydomain.example :\
12513 rqps@mydomain hostmaster@mydomain.example,\
12514 postmaster@mydomain.example
12516 .cindex "&$domain$&"
12517 .cindex "&$local_part$&"
12518 The address list is expanded before use. The expansion variables &$local_part$&
12519 and &$domain$& are set from the original recipient of the error message, and if
12520 there was any wildcard matching in the pattern, the expansion
12521 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
12522 variables &$0$&, &$1$&, etc. are set in the normal way.
12525 .option errors_reply_to main string unset
12526 .cindex "bounce message" "&'Reply-to:'& in"
12528 By default, Exim's bounce and delivery warning messages contain the header line
12530 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
12532 .oindex &%quota_warn_message%&
12533 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
12534 A warning message that is generated by the &%quota_warn_message%& option in an
12535 &(appendfile)& transport may contain its own &'From:'& header line that
12536 overrides the default.
12538 Experience shows that people reply to bounce messages. If the
12539 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
12540 and warning messages. For example:
12542 errors_reply_to = postmaster@my.domain.example
12544 The value of the option is not expanded. It must specify a valid RFC 2822
12545 address. However, if a warning message that is generated by the
12546 &%quota_warn_message%& option in an &(appendfile)& transport contain its
12547 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
12552 .option exim_group main string "compile-time configured"
12553 .cindex "gid (group id)" "Exim's own"
12554 .cindex "Exim group"
12555 This option changes the gid under which Exim runs when it gives up root
12556 privilege. The default value is compiled into the binary. The value of this
12557 option is used only when &%exim_user%& is also set. Unless it consists entirely
12558 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
12559 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
12563 .option exim_path main string "see below"
12564 .cindex "Exim binary" "path name"
12565 This option specifies the path name of the Exim binary, which is used when Exim
12566 needs to re-exec itself. The default is set up to point to the file &'exim'& in
12567 the directory configured at compile time by the BIN_DIRECTORY setting. It
12568 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
12570 &*Warning*&: Do not use a macro to define the value of this option, because
12571 you will break those Exim utilities that scan the configuration file to find
12572 where the binary is. (They then use the &%-bP%& option to extract option
12573 settings such as the value of &%spool_directory%&.)
12576 .option exim_user main string "compile-time configured"
12577 .cindex "uid (user id)" "Exim's own"
12578 .cindex "Exim user"
12579 This option changes the uid under which Exim runs when it gives up root
12580 privilege. The default value is compiled into the binary. Ownership of the run
12581 time configuration file and the use of the &%-C%& and &%-D%& command line
12582 options is checked against the values in the binary, not what is set here.
12584 Unless it consists entirely of digits, the string is looked up using
12585 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
12586 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
12587 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
12590 .option extra_local_interfaces main "string list" unset
12591 This option defines network interfaces that are to be considered local when
12592 routing, but which are not used for listening by the daemon. See section
12593 &<<SECTreclocipadd>>& for details.
12596 .option "extract_addresses_remove_ &~arguments" main boolean true
12597 .cindex "&%-t%& option"
12598 .cindex "command line" "addresses with &%-t%&"
12599 .cindex "Sendmail compatibility" "&%-t%& option"
12600 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
12601 are present on the command line when the &%-t%& option is used to build an
12602 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
12603 line addresses are removed from the recipients list. This is also how Smail
12604 behaves. However, other Sendmail documentation (the O'Reilly book) states that
12605 command line addresses are added to those obtained from the header lines. When
12606 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
12607 argument headers. If it is set false, Exim adds rather than removes argument
12611 .option finduser_retries main integer 0
12612 .cindex "NIS" "looking up users; retrying"
12613 On systems running NIS or other schemes in which user and group information is
12614 distributed from a remote system, there can be times when &[getpwnam()]& and
12615 related functions fail, even when given valid data, because things time out.
12616 Unfortunately these failures cannot be distinguished from genuine &"not found"&
12617 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
12618 many extra times to find a user or a group, waiting for one second between
12621 .cindex "&_/etc/passwd_&" "multiple reading of"
12622 You should not set this option greater than zero if your user information is in
12623 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
12624 search the file multiple times for non-existent users, and also cause delay.
12628 .option freeze_tell main "string list, comma separated" unset
12629 .cindex "freezing messages" "sending a message when freezing"
12630 On encountering certain errors, or when configured to do so in a system filter,
12631 ACL, or special router, Exim freezes a message. This means that no further
12632 delivery attempts take place until an administrator thaws the message, or the
12633 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
12634 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
12635 warning message whenever it freezes something, unless the message it is
12636 freezing is a locally-generated bounce message. (Without this exception there
12637 is the possibility of looping.) The warning message is sent to the addresses
12638 supplied as the comma-separated value of this option. If several of the
12639 message's addresses cause freezing, only a single message is sent. If the
12640 freezing was automatic, the reason(s) for freezing can be found in the message
12641 log. If you configure freezing in a filter or ACL, you must arrange for any
12642 logging that you require.
12645 .option gecos_name main string&!! unset
12647 .cindex "&""gecos""& field" "parsing"
12648 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
12649 password file to hold other information in addition to users' real names. Exim
12650 looks up this field for use when it is creating &'Sender:'& or &'From:'&
12651 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
12652 of the field are used unchanged, except that, if an ampersand is encountered,
12653 it is replaced by the user's login name with the first character forced to
12654 upper case, since this is a convention that is observed on many systems.
12656 When these options are set, &%gecos_pattern%& is treated as a regular
12657 expression that is to be applied to the field (again with && replaced by the
12658 login name), and if it matches, &%gecos_name%& is expanded and used as the
12661 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
12662 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
12663 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
12664 name terminates at the first comma, the following can be used:
12666 gecos_pattern = ([^,]*)
12670 .option gecos_pattern main string unset
12671 See &%gecos_name%& above.
12674 .option headers_charset main string "see below"
12675 This option sets a default character set for translating from encoded MIME
12676 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
12677 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
12678 ultimate default is ISO-8859-1. For more details see the description of header
12679 insertions in section &<<SECTexpansionitems>>&.
12683 .option header_maxsize main integer "see below"
12684 .cindex "header section" "maximum size of"
12685 .cindex "limit" "size of message header section"
12686 This option controls the overall maximum size of a message's header
12687 section. The default is the value of HEADER_MAXSIZE in
12688 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
12689 sections are rejected.
12692 .option header_line_maxsize main integer 0
12693 .cindex "header lines" "maximum size of"
12694 .cindex "limit" "size of one header line"
12695 This option limits the length of any individual header line in a message, after
12696 all the continuations have been joined together. Messages with individual
12697 header lines that are longer than the limit are rejected. The default value of
12698 zero means &"no limit"&.
12703 .option helo_accept_junk_hosts main "host list&!!" unset
12704 .cindex "HELO" "accepting junk data"
12705 .cindex "EHLO" "accepting junk data"
12706 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
12707 mail, and gives an error response for invalid data. Unfortunately, there are
12708 some SMTP clients that send syntactic junk. They can be accommodated by setting
12709 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
12710 if you want to do semantic checking.
12711 See also &%helo_allow_chars%& for a way of extending the permitted character
12715 .option helo_allow_chars main string unset
12716 .cindex "HELO" "underscores in"
12717 .cindex "EHLO" "underscores in"
12718 .cindex "underscore in EHLO/HELO"
12719 This option can be set to a string of rogue characters that are permitted in
12720 all EHLO and HELO names in addition to the standard letters, digits,
12721 hyphens, and dots. If you really must allow underscores, you can set
12723 helo_allow_chars = _
12725 Note that the value is one string, not a list.
12728 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
12729 .cindex "HELO" "forcing reverse lookup"
12730 .cindex "EHLO" "forcing reverse lookup"
12731 If the domain given by a client in a HELO or EHLO command matches this
12732 list, a reverse lookup is done in order to establish the host's true name. The
12733 default forces a lookup if the client host gives the server's name or any of
12734 its IP addresses (in brackets), something that broken clients have been seen to
12738 .option helo_try_verify_hosts main "host list&!!" unset
12739 .cindex "HELO verifying" "optional"
12740 .cindex "EHLO verifying" "optional"
12741 By default, Exim just checks the syntax of HELO and EHLO commands (see
12742 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
12743 to do more extensive checking of the data supplied by these commands. The ACL
12744 condition &`verify`& &`=`& &`helo`& is provided to make this possible.
12745 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
12746 to force the check to occur. From release 4.53 onwards, this is no longer
12747 necessary. If the check has not been done before &`verify`& &`=`& &`helo`& is
12748 encountered, it is done at that time. Consequently, this option is obsolete.
12749 Its specification is retained here for backwards compatibility.
12751 When an EHLO or HELO command is received, if the calling host matches
12752 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
12753 EHLO command either:
12756 is an IP literal matching the calling address of the host, or
12758 .cindex "DNS" "reverse lookup"
12759 .cindex "reverse DNS lookup"
12760 matches the host name that Exim obtains by doing a reverse lookup of the
12761 calling host address, or
12763 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
12764 available) yields the calling host address.
12767 However, the EHLO or HELO command is not rejected if any of the checks
12768 fail. Processing continues, but the result of the check is remembered, and can
12769 be detected later in an ACL by the &`verify`& &`=`& &`helo`& condition.
12771 .option helo_verify_hosts main "host list&!!" unset
12772 .cindex "HELO verifying" "mandatory"
12773 .cindex "EHLO verifying" "mandatory"
12774 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
12775 backwards compatibility. For hosts that match this option, Exim checks the host
12776 name given in the HELO or EHLO in the same way as for
12777 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
12778 rejected with a 550 error, and entries are written to the main and reject logs.
12779 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
12782 .option hold_domains main "domain list&!!" unset
12783 .cindex "domain" "delaying delivery"
12784 .cindex "delivery" "delaying certain domains"
12785 This option allows mail for particular domains to be held on the queue
12786 manually. The option is overridden if a message delivery is forced with the
12787 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
12788 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
12789 item in &%hold_domains%&, no routing or delivery for that address is done, and
12790 it is deferred every time the message is looked at.
12792 This option is intended as a temporary operational measure for delaying the
12793 delivery of mail while some problem is being sorted out, or some new
12794 configuration tested. If you just want to delay the processing of some
12795 domains until a queue run occurs, you should use &%queue_domains%& or
12796 &%queue_smtp_domains%&, not &%hold_domains%&.
12798 A setting of &%hold_domains%& does not override Exim's code for removing
12799 messages from the queue if they have been there longer than the longest retry
12800 time in any retry rule. If you want to hold messages for longer than the normal
12801 retry times, insert a dummy retry rule with a long retry time.
12804 .option host_lookup main "host list&!!" unset
12805 .cindex "host name lookup" "forcing"
12806 Exim does not look up the name of a calling host from its IP address unless it
12807 is required to compare against some host list, or the host matches
12808 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
12809 option (which normally contains IP addresses rather than host names). The
12810 default configuration file contains
12814 which causes a lookup to happen for all hosts. If the expense of these lookups
12815 is felt to be too great, the setting can be changed or removed.
12817 After a successful reverse lookup, Exim does a forward lookup on the name it
12818 has obtained, to verify that it yields the IP address that it started with. If
12819 this check fails, Exim behaves as if the name lookup failed.
12821 .cindex "&$host_lookup_failed$&"
12822 .cindex "&$sender_host_name$&"
12823 After any kind of failure, the host name (in &$sender_host_name$&) remains
12824 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
12825 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and &`verify`& &`=`&
12826 &`reverse_host_lookup`& in ACLs.
12829 .option host_lookup_order main "string list" &`bydns:byaddr`&
12830 This option specifies the order of different lookup methods when Exim is trying
12831 to find a host name from an IP address. The default is to do a DNS lookup
12832 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
12833 if that fails. You can change the order of these lookups, or omit one entirely,
12836 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
12837 multiple PTR records in the DNS and the IP address is not listed in
12838 &_/etc/hosts_&. Different operating systems give different results in this
12839 case. That is why the default tries a DNS lookup first.
12843 .option host_reject_connection main "host list&!!" unset
12844 .cindex "host" "rejecting connections from"
12845 If this option is set, incoming SMTP calls from the hosts listed are rejected
12846 as soon as the connection is made.
12847 This option is obsolete, and retained only for backward compatibility, because
12848 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
12849 connections immediately.
12851 The ability to give an immediate rejection (either by this option or using an
12852 ACL) is provided for use in unusual cases. Many hosts will just try again,
12853 sometimes without much delay. Normally, it is better to use an ACL to reject
12854 incoming messages at a later stage, such as after RCPT commands. See
12855 chapter &<<CHAPACL>>&.
12858 .option hosts_connection_nolog main "host list&!!" unset
12859 .cindex "host" "not logging connections from"
12860 This option defines a list of hosts for which connection logging does not
12861 happen, even though the &%smtp_connection%& log selector is set. For example,
12862 you might want not to log SMTP connections from local processes, or from
12863 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
12864 the daemon; you should therefore strive to restrict its value to a short inline
12865 list of IP addresses and networks. To disable logging SMTP connections from
12866 local processes, you must create a host list with an empty item. For example:
12868 hosts_connection_nolog = :
12870 If the &%smtp_connection%& log selector is not set, this option has no effect.
12874 .option hosts_treat_as_local main "domain list&!!" unset
12875 .cindex "local host" "domains treated as"
12876 .cindex "host" "treated as local"
12877 If this option is set, any host names that match the domain list are treated as
12878 if they were the local host when Exim is scanning host lists obtained from MX
12880 or other sources. Note that the value of this option is a domain list, not a
12881 host list, because it is always used to check host names, not IP addresses.
12883 This option also applies when Exim is matching the special items
12884 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
12885 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
12886 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
12887 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
12888 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
12889 interfaces and recognising the local host.
12892 .option ignore_bounce_errors_after main time 10w
12893 .cindex "bounce message" "discarding"
12894 .cindex "discarding bounce message"
12895 This option affects the processing of bounce messages that cannot be delivered,
12896 that is, those that suffer a permanent delivery failure. (Bounce messages that
12897 suffer temporary delivery failures are of course retried in the usual way.)
12899 After a permanent delivery failure, bounce messages are frozen,
12900 because there is no sender to whom they can be returned. When a frozen bounce
12901 message has been on the queue for more than the given time, it is unfrozen at
12902 the next queue run, and a further delivery is attempted. If delivery fails
12903 again, the bounce message is discarded. This makes it possible to keep failed
12904 bounce messages around for a shorter time than the normal maximum retry time
12905 for frozen messages. For example,
12907 ignore_bounce_errors_after = 12h
12909 retries failed bounce message deliveries after 12 hours, discarding any further
12910 failures. If the value of this option is set to a zero time period, bounce
12911 failures are discarded immediately. Setting a very long time (as in the default
12912 value) has the effect of disabling this option. For ways of automatically
12913 dealing with other kinds of frozen message, see &%auto_thaw%& and
12914 &%timeout_frozen_after%&.
12917 .option ignore_fromline_hosts main "host list&!!" unset
12918 .cindex "&""From""& line"
12919 .cindex "UUCP" "&""From""& line"
12920 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
12921 the headers of a message. By default this is treated as the start of the
12922 message's body, which means that any following headers are not recognized as
12923 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
12924 match those hosts that insist on sending it. If the sender is actually a local
12925 process rather than a remote host, and is using &%-bs%& to inject the messages,
12926 &%ignore_fromline_local%& must be set to achieve this effect.
12929 .option ignore_fromline_local main boolean false
12930 See &%ignore_fromline_hosts%& above.
12933 .option keep_malformed main time 4d
12934 This option specifies the length of time to keep messages whose spool files
12935 have been corrupted in some way. This should, of course, never happen. At the
12936 next attempt to deliver such a message, it gets removed. The incident is
12940 .option ldap_default_servers main "string list" unset
12941 .cindex "LDAP" "default servers"
12942 This option provides a list of LDAP servers which are tried in turn when an
12943 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
12944 details of LDAP queries. This option is available only when Exim has been built
12948 .option ldap_version main integer unset
12949 .cindex "LDAP protocol version" "forcing"
12950 This option can be used to force Exim to set a specific protocol version for
12951 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
12952 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
12953 the LDAP headers; otherwise it is 2. This option is available only when Exim
12954 has been built with LDAP support.
12958 .option local_from_check main boolean true
12959 .cindex "&'Sender:'& header line" "disabling addition of"
12960 .cindex "&'From:'& header line" "disabling checking of"
12961 When a message is submitted locally (that is, not over a TCP/IP connection) by
12962 an untrusted user, Exim removes any existing &'Sender:'& header line, and
12963 checks that the &'From:'& header line matches the login of the calling user and
12964 the domain specified by &%qualify_domain%&.
12966 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
12967 locally submitted message is automatically qualified by Exim, unless the
12968 &%-bnq%& command line option is used.
12970 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
12971 on the local part. If the &'From:'& header line does not match, Exim adds a
12972 &'Sender:'& header with an address constructed from the calling user's login
12973 and the default qualify domain.
12975 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
12976 and no &'Sender:'& header is ever added. If, in addition, you want to retain
12977 &'Sender:'& header lines supplied by untrusted users, you must also set
12978 &%local_sender_retain%& to be true.
12980 .cindex "envelope sender"
12981 These options affect only the header lines in the message. The envelope sender
12982 is still forced to be the login id at the qualify domain unless
12983 &%untrusted_set_sender%& permits the user to supply an envelope sender.
12985 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
12986 request similar header line checking. See section &<<SECTthesenhea>>&, which
12987 has more details about &'Sender:'& processing.
12992 .option local_from_prefix main string unset
12993 When Exim checks the &'From:'& header line of locally submitted messages for
12994 matching the login id (see &%local_from_check%& above), it can be configured to
12995 ignore certain prefixes and suffixes in the local part of the address. This is
12996 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
12997 appropriate lists, in the same form as the &%local_part_prefix%& and
12998 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
13001 local_from_prefix = *-
13003 is set, a &'From:'& line containing
13005 From: anything-user@your.domain.example
13007 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
13008 matches the actual sender address that is constructed from the login name and
13012 .option local_from_suffix main string unset
13013 See &%local_from_prefix%& above.
13016 .option local_interfaces main "string list" "see below"
13017 This option controls which network interfaces are used by the daemon for
13018 listening; they are also used to identify the local host when routing. Chapter
13019 &<<CHAPinterfaces>>& contains a full description of this option and the related
13020 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
13021 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
13022 &%local_interfaces%& is
13024 local_interfaces = 0.0.0.0
13026 when Exim is built without IPv6 support; otherwise it is
13028 local_interfaces = <; ::0 ; 0.0.0.0
13031 .option local_scan_timeout main time 5m
13032 .cindex "timeout" "for &[local_scan()]& function"
13033 .cindex "&[local_scan()]& function" "timeout"
13034 This timeout applies to the &[local_scan()]& function (see chapter
13035 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
13036 the incoming message is rejected with a temporary error if it is an SMTP
13037 message. For a non-SMTP message, the message is dropped and Exim ends with a
13038 non-zero code. The incident is logged on the main and reject logs.
13042 .option local_sender_retain main boolean false
13043 .cindex "&'Sender:'& header line" "retaining from local submission"
13044 When a message is submitted locally (that is, not over a TCP/IP connection) by
13045 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
13046 do not want this to happen, you must set &%local_sender_retain%&, and you must
13047 also set &%local_from_check%& to be false (Exim will complain if you do not).
13048 See also the ACL modifier &`control = suppress_local_fixups`&. Section
13049 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
13054 .option localhost_number main string&!! unset
13055 .cindex "host" "locally unique number for"
13056 .cindex "message ids" "with multiple hosts"
13057 .cindex "&$localhost_number$&"
13058 Exim's message ids are normally unique only within the local host. If
13059 uniqueness among a set of hosts is required, each host must set a different
13060 value for the &%localhost_number%& option. The string is expanded immediately
13061 after reading the configuration file (so that a number can be computed from the
13062 host name, for example) and the result of the expansion must be a number in the
13063 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
13064 systems). This is available in subsequent string expansions via the variable
13065 &$localhost_number$&. When &%localhost_number is set%&, the final two
13066 characters of the message id, instead of just being a fractional part of the
13067 time, are computed from the time and the local host number as described in
13068 section &<<SECTmessiden>>&.
13072 .option log_file_path main "string list&!!" "set at compile time"
13073 .cindex "log" "file path for"
13074 This option sets the path which is used to determine the names of Exim's log
13075 files, or indicates that logging is to be to syslog, or both. It is expanded
13076 when Exim is entered, so it can, for example, contain a reference to the host
13077 name. If no specific path is set for the log files at compile or run time, they
13078 are written in a sub-directory called &_log_& in Exim's spool directory.
13079 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
13080 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
13081 used. If this string is fixed at your installation (contains no expansion
13082 variables) it is recommended that you do not set this option in the
13083 configuration file, but instead supply the path using LOG_FILE_PATH in
13084 &_Local/Makefile_& so that it is available to Exim for logging errors detected
13085 early on &-- in particular, failure to read the configuration file.
13088 .option log_selector main string unset
13089 .cindex "log" "selectors"
13090 This option can be used to reduce or increase the number of things that Exim
13091 writes to its log files. Its argument is made up of names preceded by plus or
13092 minus characters. For example:
13094 log_selector = +arguments -retry_defer
13096 A list of possible names and what they control is given in the chapter on
13097 logging, in section &<<SECTlogselector>>&.
13100 .option log_timezone main boolean false
13101 .cindex "log" "timezone for entries"
13102 .cindex "&$tod_log$&"
13103 .cindex "&$tod_zone$&"
13104 By default, the timestamps on log lines are in local time without the
13105 timezone. This means that if your timezone changes twice a year, the timestamps
13106 in log lines are ambiguous for an hour when the clocks go back. One way of
13107 avoiding this problem is to set the timezone to UTC. An alternative is to set
13108 &%log_timezone%& true. This turns on the addition of the timezone offset to
13109 timestamps in log lines. Turning on this option can add quite a lot to the size
13110 of log files because each line is extended by 6 characters. Note that the
13111 &$tod_log$& variable contains the log timestamp without the zone, but there is
13112 another variable called &$tod_zone$& that contains just the timezone offset.
13115 .option lookup_open_max main integer 25
13116 .cindex "too many open files"
13117 .cindex "open files" "too many"
13118 .cindex "file" "too many open"
13119 .cindex "lookup" "maximum open files"
13120 .cindex "limit" "open files for lookups"
13121 This option limits the number of simultaneously open files for single-key
13122 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
13123 Exim normally keeps these files open during routing, because often the same
13124 file is required several times. If the limit is reached, Exim closes the least
13125 recently used file. Note that if you are using the &'ndbm'& library, it
13126 actually opens two files for each logical DBM database, though it still counts
13127 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
13128 open files"& errors with NDBM, you need to reduce the value of
13129 &%lookup_open_max%&.
13132 .option max_username_length main integer 0
13133 .cindex "length" "of login name"
13134 .cindex "user name" "maximum length"
13135 .cindex "limit" "user name length"
13136 Some operating systems are broken in that they truncate long arguments to
13137 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
13138 this option is set greater than zero, any attempt to call &[getpwnam()]& with
13139 an argument that is longer behaves as if &[getpwnam()]& failed.
13143 .option message_body_visible main integer 500
13144 .cindex "body of message" "visible size"
13145 .cindex "message body" "visible size"
13146 .cindex "&$message_body$&"
13147 .cindex "&$message_body_end$&"
13148 This option specifies how much of a message's body is to be included in the
13149 &$message_body$& and &$message_body_end$& expansion variables.
13152 .option message_id_header_domain main string&!! unset
13153 .cindex "&'Message-ID:'& header line"
13154 If this option is set, the string is expanded and used as the right hand side
13155 (domain) of the &'Message-ID:'& header that Exim creates if a
13156 locally-originated incoming message does not have one. &"Locally-originated"&
13157 means &"not received over TCP/IP."&
13158 Otherwise, the primary host name is used.
13159 Only letters, digits, dot and hyphen are accepted; any other characters are
13160 replaced by hyphens. If the expansion is forced to fail, or if the result is an
13161 empty string, the option is ignored.
13164 .option message_id_header_text main string&!! unset
13165 If this variable is set, the string is expanded and used to augment the text of
13166 the &'Message-id:'& header that Exim creates if a locally-originated incoming
13167 message does not have one. The text of this header is required by RFC 2822 to
13168 take the form of an address. By default, Exim uses its internal message id as
13169 the local part, and the primary host name as the domain. If this option is set,
13170 it is expanded, and provided the expansion is not forced to fail, and does not
13171 yield an empty string, the result is inserted into the header immediately
13172 before the @, separated from the internal message id by a dot. Any characters
13173 that are illegal in an address are automatically converted into hyphens. This
13174 means that variables such as &$tod_log$& can be used, because the spaces and
13175 colons will become hyphens.
13178 .option message_logs main boolean true
13179 .cindex "message log" "disabling"
13180 .cindex "log" "message log; disabling"
13181 If this option is turned off, per-message log files are not created in the
13182 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
13183 Exim, by reducing the number of files involved in handling a message from a
13184 minimum of four (header spool file, body spool file, delivery journal, and
13185 per-message log) to three. The other major I/O activity is Exim's main log,
13186 which is not affected by this option.
13189 .option message_size_limit main string&!! 50M
13190 .cindex "message" "size limit"
13191 .cindex "limit" "message size"
13192 .cindex "size of message" "limit"
13193 This option limits the maximum size of message that Exim will process. The
13194 value is expanded for each incoming
13195 connection so, for example, it can be made to depend on the IP address of the
13196 remote host for messages arriving via TCP/IP. &*Note*&: This limit cannot be
13197 made to depend on a message's sender or any other properties of an individual
13198 message, because it has to be advertised in the server's response to EHLO.
13199 String expansion failure causes a temporary error. A value of zero means no
13200 limit, but its use is not recommended. See also &%bounce_return_size_limit%&.
13202 Incoming SMTP messages are failed with a 552 error if the limit is
13203 exceeded; locally-generated messages either get a stderr message or a delivery
13204 failure message to the sender, depending on the &%-oe%& setting. Rejection of
13205 an oversized message is logged in both the main and the reject logs. See also
13206 the generic transport option &%message_size_limit%&, which limits the size of
13207 message that an individual transport can process.
13210 .option move_frozen_messages main boolean false
13211 .cindex "frozen messages" "moving"
13212 This option, which is available only if Exim has been built with the setting
13214 SUPPORT_MOVE_FROZEN_MESSAGES=yes
13216 in &_Local/Makefile_&, causes frozen messages and their message logs to be
13217 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
13218 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
13219 standard utilities for handling such moved messages, and they do not show up in
13220 lists generated by &%-bp%& or by the Exim monitor.
13223 .option mua_wrapper main boolean false
13224 Setting this option true causes Exim to run in a very restrictive mode in which
13225 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
13226 contains a full description of this facility.
13230 .option mysql_servers main "string list" unset
13231 .cindex "MySQL" "server list"
13232 This option provides a list of MySQL servers and associated connection data, to
13233 be used in conjunction with &(mysql)& lookups (see section &<<SECTsql>>&). The
13234 option is available only if Exim has been built with MySQL support.
13237 .option never_users main "string list&!!" unset
13238 This option is expanded just once, at the start of Exim's processing. Local
13239 message deliveries are normally run in processes that are setuid to the
13240 recipient, and remote deliveries are normally run under Exim's own uid and gid.
13241 It is usually desirable to prevent any deliveries from running as root, as a
13244 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
13245 list of users that must not be used for local deliveries. This list is fixed in
13246 the binary and cannot be overridden by the configuration file. By default, it
13247 contains just the single user name &"root"&. The &%never_users%& runtime option
13248 can be used to add more users to the fixed list.
13250 If a message is to be delivered as one of the users on the fixed list or the
13251 &%never_users%& list, an error occurs, and delivery is deferred. A common
13254 never_users = root:daemon:bin
13256 Including root is redundant if it is also on the fixed list, but it does no
13257 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
13261 .option oracle_servers main "string list" unset
13262 .cindex "Oracle" "server list"
13263 This option provides a list of Oracle servers and associated connection data,
13264 to be used in conjunction with &(oracle)& lookups (see section &<<SECTsql>>&).
13265 The option is available only if Exim has been built with Oracle support.
13268 .option percent_hack_domains main "domain list&!!" unset
13269 .cindex "&""percent hack""&"
13270 .cindex "source routing" "in email address"
13271 .cindex "address" "source-routed"
13272 The &"percent hack"& is the convention whereby a local part containing a
13273 percent sign is re-interpreted as a new email address, with the percent
13274 replaced by @. This is sometimes called &"source routing"&, though that term is
13275 also applied to RFC 2822 addresses that begin with an @ character. If this
13276 option is set, Exim implements the percent facility for those domains listed,
13277 but no others. This happens before an incoming SMTP address is tested against
13280 &*Warning*&: The &"percent hack"& has often been abused by people who are
13281 trying to get round relaying restrictions. For this reason, it is best avoided
13282 if at all possible. Unfortunately, a number of less security-conscious MTAs
13283 implement it unconditionally. If you are running Exim on a gateway host, and
13284 routing mail through to internal MTAs without processing the local parts, it is
13285 a good idea to reject recipient addresses with percent characters in their
13286 local parts. Exim's default configuration does this.
13289 .option perl_at_start main boolean false
13290 This option is available only when Exim is built with an embedded Perl
13291 interpreter. See chapter &<<CHAPperl>>& for details of its use.
13294 .option perl_startup main string unset
13295 This option is available only when Exim is built with an embedded Perl
13296 interpreter. See chapter &<<CHAPperl>>& for details of its use.
13299 .option pgsql_servers main "string list" unset
13300 .cindex "PostgreSQL lookup type" "server list"
13301 This option provides a list of PostgreSQL servers and associated connection
13302 data, to be used in conjunction with &(pgsql)& lookups (see section
13303 &<<SECTsql>>&). The option is available only if Exim has been built with
13304 PostgreSQL support.
13307 .option pid_file_path main string&!! "set at compile time"
13308 .cindex "daemon" "pid file path"
13309 .cindex "pid file" "path for"
13310 This option sets the name of the file to which the Exim daemon writes its
13311 process id. The string is expanded, so it can contain, for example, references
13314 pid_file_path = /var/log/$primary_hostname/exim.pid
13316 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
13318 The value set by the option can be overridden by the &%-oP%& command line
13319 option. A pid file is not written if a &"non-standard"& daemon is run by means
13320 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
13323 .option pipelining_advertise_hosts main "host list&!!" *
13324 .cindex "PIPELINING advertising" "suppressing"
13325 This option can be used to suppress the advertisement of the SMTP
13326 PIPELINING extension to specific hosts. When PIPELINING is not
13327 advertised and &%smtp_enforce_sync%& is true, an Exim server enforces strict
13328 synchronization for each SMTP command and response.
13329 When PIPELINING is advertised, Exim assumes that clients will use it; &"out
13330 of order"& commands that are &"expected"& do not count as protocol errors (see
13331 &%smtp_max_synprot_errors%&).
13334 .option preserve_message_logs main boolean false
13335 .cindex "message logs" "preserving"
13336 If this option is set, message log files are not deleted when messages are
13337 completed. Instead, they are moved to a sub-directory of the spool directory
13338 called &_msglog.OLD_&, where they remain available for statistical or debugging
13339 purposes. This is a dangerous option to set on systems with any appreciable
13340 volume of mail. Use with care!
13343 .option primary_hostname main string "see below"
13344 .cindex "name" "of local host"
13345 .cindex "host" "name of local"
13346 .cindex "local host" "name of"
13347 .cindex "&$primary_hostname$&"
13348 This specifies the name of the current host. It is used in the default EHLO or
13349 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
13350 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
13351 The value is also used by default in some SMTP response messages from an Exim
13352 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
13354 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
13355 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
13356 contains only one component, Exim passes it to &[gethostbyname()]& (or
13357 &[getipnodebyname()]& when available) in order to obtain the fully qualified
13358 version. The variable &$primary_hostname$& contains the host name, whether set
13359 explicitly by this option, or defaulted.
13362 .option print_topbitchars main boolean false
13363 .cindex "printing characters"
13364 .cindex "8-bit characters"
13365 By default, Exim considers only those characters whose codes lie in the range
13366 32&--126 to be printing characters. In a number of circumstances (for example,
13367 when writing log entries) non-printing characters are converted into escape
13368 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
13369 is set, code values of 128 and above are also considered to be printing
13373 .option process_log_path main string unset
13374 .cindex "process log path"
13375 .cindex "log" "process log"
13376 .cindex "&'exiwhat'&"
13377 This option sets the name of the file to which an Exim process writes its
13378 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
13379 utility script. If this option is unset, the file called &_exim-process.info_&
13380 in Exim's spool directory is used. The ability to specify the name explicitly
13381 can be useful in environments where two different Exims are running, using
13382 different spool directories.
13385 .option prod_requires_admin main boolean true
13386 .cindex "&%-M%& option"
13387 .cindex "&%-R%& option"
13388 .cindex "&%-q%& option"
13389 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
13390 admin user unless &%prod_requires_admin%& is set false. See also
13391 &%queue_list_requires_admin%&.
13394 .option qualify_domain main string "see below"
13395 .cindex "domain" "for qualifying addresses"
13396 .cindex "address" "qualification"
13397 This option specifies the domain name that is added to any envelope sender
13398 addresses that do not have a domain qualification. It also applies to
13399 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
13400 are accepted by default only for locally-generated messages. Qualification is
13401 also applied to addresses in header lines such as &'From:'& and &'To:'& for
13402 locally-generated messages, unless the &%-bnq%& command line option is used.
13404 Messages from external sources must always contain fully qualified addresses,
13405 unless the sending host matches &%sender_unqualified_hosts%& or
13406 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
13407 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
13408 necessary. Internally, Exim always works with fully qualified envelope
13409 addresses. If &%qualify_domain%& is not set, it defaults to the
13410 &%primary_hostname%& value.
13413 .option qualify_recipient main string "see below"
13414 This option allows you to specify a different domain for qualifying recipient
13415 addresses to the one that is used for senders. See &%qualify_domain%& above.
13419 .option queue_domains main "domain list&!!" unset
13420 .cindex "domain" "specifying non-immediate delivery"
13421 .cindex "queueing incoming messages"
13422 .cindex "message" "queueing certain domains"
13423 This option lists domains for which immediate delivery is not required.
13424 A delivery process is started whenever a message is received, but only those
13425 domains that do not match are processed. All other deliveries wait until the
13426 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
13429 .option queue_list_requires_admin main boolean true
13430 .cindex "&%-bp%& option"
13431 The &%-bp%& command-line option, which lists the messages that are on the
13432 queue, requires the caller to be an admin user unless
13433 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
13436 .option queue_only main boolean false
13437 .cindex "queueing incoming messages"
13438 .cindex "message" "queueing unconditionally"
13439 If &%queue_only%& is set, a delivery process is not automatically started
13440 whenever a message is received. Instead, the message waits on the queue for the
13441 next queue run. Even if &%queue_only%& is false, incoming messages may not get
13442 delivered immediately when certain conditions (such as heavy load) occur.
13444 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
13445 and &%-odi%& command line options override &%queue_only%& unless
13446 &%queue_only_override%& is set false. See also &%queue_only_file%&,
13447 &%queue_only_load%&, and &%smtp_accept_queue%&.
13450 .option queue_only_file main string unset
13451 .cindex "queueing incoming messages"
13452 .cindex "message" "queueing by file existence"
13453 This option can be set to a colon-separated list of absolute path names, each
13454 one optionally preceded by &"smtp"&. When Exim is receiving a message,
13455 it tests for the existence of each listed path using a call to &[stat()]&. For
13456 each path that exists, the corresponding queuing option is set.
13457 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
13458 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
13460 queue_only_file = smtp/some/file
13462 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
13463 &_/some/file_& exists.
13466 .option queue_only_load main fixed-point unset
13467 .cindex "load average"
13468 .cindex "queueing incoming messages"
13469 .cindex "message" "queueing by load"
13470 If the system load average is higher than this value, incoming messages from
13471 all sources are queued, and no automatic deliveries are started. If this
13472 happens during local or remote SMTP input, all subsequent messages on the same
13473 connection are queued. Deliveries will subsequently be performed by queue
13474 runner processes. This option has no effect on ancient operating systems on
13475 which Exim cannot determine the load average. See also
13476 &%deliver_queue_load_max%& and &%smtp_load_reserve%&.
13479 .option queue_only_override main boolean true
13480 .cindex "queueing incoming messages"
13481 When this option is true, the &%-od%&&'x'& command line options override the
13482 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
13483 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
13484 to override; they are accepted, but ignored.
13487 .option queue_run_in_order main boolean false
13488 .cindex "queue runner" "processing messages in order"
13489 If this option is set, queue runs happen in order of message arrival instead of
13490 in an arbitrary order. For this to happen, a complete list of the entire queue
13491 must be set up before the deliveries start. When the queue is all held in a
13492 single directory (the default),
13494 a single list is created for both the ordered and the non-ordered cases.
13495 However, if &%split_spool_directory%& is set, a single list is not created when
13496 &%queue_run_in_order%& is false. In this case, the sub-directories are
13497 processed one at a time (in a random order), and this avoids setting up one
13498 huge list for the whole queue. Thus, setting &%queue_run_in_order%& with
13499 &%split_spool_directory%& may degrade performance when the queue is large,
13500 because of the extra work in setting up the single, large list. In most
13501 situations, &%queue_run_in_order%& should not be set.
13505 .option queue_run_max main integer 5
13506 .cindex "queue runner" "maximum number of"
13507 This controls the maximum number of queue runner processes that an Exim daemon
13508 can run simultaneously. This does not mean that it starts them all at once,
13509 but rather that if the maximum number are still running when the time comes to
13510 start another one, it refrains from starting another one. This can happen with
13511 very large queues and/or very sluggish deliveries. This option does not,
13512 however, interlock with other processes, so additional queue runners can be
13513 started by other means, or by killing and restarting the daemon.
13515 Setting this option to zero does not suppress queue runs; rather, it disables
13516 the limit, allowing any number of simultaneous queue runner processes to be
13517 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
13518 the daemon's command line.
13520 .option queue_smtp_domains main "domain list&!!" unset
13521 .cindex "queueing incoming messages"
13522 .cindex "message" "queueing remote deliveries"
13523 When this option is set, a delivery process is started whenever a message is
13524 received, routing is performed, and local deliveries take place.
13525 However, if any SMTP deliveries are required for domains that match
13526 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
13527 message waits on the queue for the next queue run. Since routing of the message
13528 has taken place, Exim knows to which remote hosts it must be delivered, and so
13529 when the queue run happens, multiple messages for the same host are delivered
13530 over a single SMTP connection. The &%-odqs%& command line option causes all
13531 SMTP deliveries to be queued in this way, and is equivalent to setting
13532 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
13536 .option receive_timeout main time 0s
13537 .cindex "timeout" "for non-SMTP input"
13538 This option sets the timeout for accepting a non-SMTP message, that is, the
13539 maximum time that Exim waits when reading a message on the standard input. If
13540 the value is zero, it will wait for ever. This setting is overridden by the
13541 &%-or%& command line option. The timeout for incoming SMTP messages is
13542 controlled by &%smtp_receive_timeout%&.
13544 .option received_header_text main string&!! "see below"
13545 .cindex "customizing" "&'Received:'& header"
13546 .cindex "&'Received:'& header line" "customizing"
13547 This string defines the contents of the &'Received:'& message header that is
13548 added to each message, except for the timestamp, which is automatically added
13549 on at the end (preceded by a semicolon). The string is expanded each time it is
13550 used. If the expansion yields an empty string, no &'Received:'& header line is
13551 added to the message. Otherwise, the string should start with the text
13552 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
13553 header lines. The default setting is:
13556 received_header_text = Received: \
13557 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
13558 {${if def:sender_ident \
13559 {from ${quote_local_part:$sender_ident} }}\
13560 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
13561 by $primary_hostname \
13562 ${if def:received_protocol {with $received_protocol}} \
13563 ${if def:tls_cipher {($tls_cipher)\n\t}}\
13564 (Exim $version_number)\n\t\
13565 ${if def:sender_address \
13566 {(envelope-from <$sender_address>)\n\t}}\
13567 id $message_exim_id\
13568 ${if def:received_for {\n\tfor $received_for}}
13571 The reference to the TLS cipher is omitted when Exim is built without TLS
13572 support. The use of conditional expansions ensures that this works for both
13573 locally generated messages and messages received from remote hosts, giving
13574 header lines such as the following:
13576 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
13577 by marley.carol.example with esmtp (Exim 4.00)
13578 (envelope-from <bob@carol.example>)
13579 id 16IOWa-00019l-00
13580 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
13581 Received: by scrooge.carol.example with local (Exim 4.00)
13582 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
13584 Until the body of the message has been received, the timestamp is the time when
13585 the message started to be received. Once the body has arrived, and all policy
13586 checks have taken place, the timestamp is updated to the time at which the
13587 message was accepted.
13590 .option received_headers_max main integer 30
13591 .cindex "loop" "prevention"
13592 .cindex "mail loop prevention"
13593 .cindex "&'Received:'& header line" "counting"
13594 When a message is to be delivered, the number of &'Received:'& headers is
13595 counted, and if it is greater than this parameter, a mail loop is assumed to
13596 have occurred, the delivery is abandoned, and an error message is generated.
13597 This applies to both local and remote deliveries.
13600 .option recipient_unqualified_hosts main "host list&!!" unset
13601 .cindex "unqualified addresses"
13602 .cindex "host" "unqualified addresses from"
13603 This option lists those hosts from which Exim is prepared to accept unqualified
13604 recipient addresses in message envelopes. The addresses are made fully
13605 qualified by the addition of the &%qualify_recipient%& value. This option also
13606 affects message header lines. Exim does not reject unqualified recipient
13607 addresses in headers, but it qualifies them only if the message came from a
13608 host that matches &%recipient_unqualified_hosts%&,
13609 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
13610 option was not set.
13613 .option recipients_max main integer 0
13614 .cindex "limit" "number of recipients"
13615 .cindex "recipient" "maximum number"
13616 If this option is set greater than zero, it specifies the maximum number of
13617 original recipients for any message. Additional recipients that are generated
13618 by aliasing or forwarding do not count. SMTP messages get a 452 response for
13619 all recipients over the limit; earlier recipients are delivered as normal.
13620 Non-SMTP messages with too many recipients are failed, and no deliveries are
13623 .cindex "RCPT" "maximum number of incoming"
13624 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
13625 RCPT commands in a single message.
13628 .option recipients_max_reject main boolean false
13629 If this option is set true, Exim rejects SMTP messages containing too many
13630 recipients by giving 552 errors to the surplus RCPT commands, and a 554
13631 error to the eventual DATA command. Otherwise (the default) it gives a 452
13632 error to the surplus RCPT commands and accepts the message on behalf of the
13633 initial set of recipients. The remote server should then re-send the message
13634 for the remaining recipients at a later time.
13637 .option remote_max_parallel main integer 2
13638 .cindex "delivery" "parallelism for remote"
13639 This option controls parallel delivery of one message to a number of remote
13640 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
13641 does all the remote deliveries for a message one by one. Otherwise, if a single
13642 message has to be delivered to more than one remote host, or if several copies
13643 have to be sent to the same remote host, up to &%remote_max_parallel%&
13644 deliveries are done simultaneously. If more than &%remote_max_parallel%&
13645 deliveries are required, the maximum number of processes are started, and as
13646 each one finishes, another is begun. The order of starting processes is the
13647 same as if sequential delivery were being done, and can be controlled by the
13648 &%remote_sort_domains%& option. If parallel delivery takes place while running
13649 with debugging turned on, the debugging output from each delivery process is
13650 tagged with its process id.
13652 This option controls only the maximum number of parallel deliveries for one
13653 message in one Exim delivery process. Because Exim has no central queue
13654 manager, there is no way of controlling the total number of simultaneous
13655 deliveries if the configuration allows a delivery attempt as soon as a message
13658 .cindex "number of deliveries"
13659 .cindex "delivery" "maximum number of"
13660 If you want to control the total number of deliveries on the system, you
13661 need to set the &%queue_only%& option. This ensures that all incoming messages
13662 are added to the queue without starting a delivery process. Then set up an Exim
13663 daemon to start queue runner processes at appropriate intervals (probably
13664 fairly often, for example, every minute), and limit the total number of queue
13665 runners by setting the &%queue_run_max%& parameter. Because each queue runner
13666 delivers only one message at a time, the maximum number of deliveries that can
13667 then take place at once is &%queue_run_max%& multiplied by
13668 &%remote_max_parallel%&.
13670 If it is purely remote deliveries you want to control, use
13671 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
13672 doing the SMTP routing before queuing, so that several messages for the same
13673 host will eventually get delivered down the same connection.
13676 .option remote_sort_domains main "domain list&!!" unset
13677 .cindex "sorting remote deliveries"
13678 .cindex "delivery" "sorting remote"
13679 When there are a number of remote deliveries for a message, they are sorted by
13680 domain into the order given by this list. For example,
13682 remote_sort_domains = *.cam.ac.uk:*.uk
13684 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
13685 then to those in the &%uk%& domain, then to any others.
13688 .option retry_data_expire main time 7d
13689 .cindex "hints database" "data expiry"
13690 This option sets a &"use before"& time on retry information in Exim's hints
13691 database. Any older retry data is ignored. This means that, for example, once a
13692 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
13696 .option retry_interval_max main time 24h
13697 .cindex "retry" "limit on interval"
13698 .cindex "limit" "on retry interval"
13700 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
13701 intervals between delivery attempts for messages that cannot be delivered
13702 straight away. This option sets an overall limit to the length of time between
13703 retries. It cannot be set greater than 24 hours; any attempt to do so forces
13708 .option return_path_remove main boolean true
13709 .cindex "&'Return-path:'& header line" "removing"
13710 RFC 2821, section 4.4, states that an SMTP server must insert a
13711 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
13712 The &'Return-path:'& header preserves the sender address as received in the
13713 MAIL command. This description implies that this header should not be present
13714 in an incoming message. If &%return_path_remove%& is true, any existing
13715 &'Return-path:'& headers are removed from messages at the time they are
13716 received. Exim's transports have options for adding &'Return-path:'& headers at
13717 the time of delivery. They are normally used only for final local deliveries.
13720 .option return_size_limit main integer 100K
13721 This option is an obsolete synonym for &%bounce_return_size_limit%&.
13724 .option rfc1413_hosts main "host list&!!" *
13726 .cindex "host" "for RFC 1413 calls"
13727 RFC 1413 identification calls are made to any client host which matches an item
13731 .option rfc1413_query_timeout main time 5s
13733 .cindex "RFC 1413" "query timeout"
13734 .cindex "timeout" "for RFC 1413 call"
13735 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
13736 no RFC 1413 calls are ever made.
13739 .option sender_unqualified_hosts main "host list&!!" unset
13740 .cindex "unqualified addresses"
13741 .cindex "host" "unqualified addresses from"
13742 This option lists those hosts from which Exim is prepared to accept unqualified
13743 sender addresses. The addresses are made fully qualified by the addition of
13744 &%qualify_domain%&. This option also affects message header lines. Exim does
13745 not reject unqualified addresses in headers that contain sender addresses, but
13746 it qualifies them only if the message came from a host that matches
13747 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
13748 using TCP/IP), and the &%-bnq%& option was not set.
13751 .option smtp_accept_keepalive main boolean true
13752 .cindex "keepalive" "on incoming connection"
13753 This option controls the setting of the SO_KEEPALIVE option on incoming
13754 TCP/IP socket connections. When set, it causes the kernel to probe idle
13755 connections periodically, by sending packets with &"old"& sequence numbers. The
13756 other end of the connection should send an acknowledgement if the connection is
13757 still okay or a reset if the connection has been aborted. The reason for doing
13758 this is that it has the beneficial effect of freeing up certain types of
13759 connection that can get stuck when the remote host is disconnected without
13760 tidying up the TCP/IP call properly. The keepalive mechanism takes several
13761 hours to detect unreachable hosts.
13765 .option smtp_accept_max main integer 20
13766 .cindex "limit" "incoming SMTP connections"
13767 .cindex "SMTP" "incoming connection count"
13769 This option specifies the maximum number of simultaneous incoming SMTP calls
13770 that Exim will accept. It applies only to the listening daemon; there is no
13771 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
13772 value is set to zero, no limit is applied. However, it is required to be
13773 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
13774 set. See also &%smtp_accept_reserve%&.
13778 .option smtp_accept_max_nonmail main integer 10
13779 .cindex "limit" "non-mail SMTP commands"
13780 .cindex "SMTP" "limiting non-mail commands"
13781 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
13782 the connection if there are too many. This option defines &"too many"&. The
13783 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
13784 client looping sending EHLO, for example. The check is applied only if the
13785 client host matches &%smtp_accept_max_nonmail_hosts%&.
13787 When a new message is expected, one occurrence of RSET is not counted. This
13788 allows a client to send one RSET between messages (this is not necessary,
13789 but some clients do it). Exim also allows one uncounted occurence of HELO
13790 or EHLO, and one occurrence of STARTTLS between messages. After
13791 starting up a TLS session, another EHLO is expected, and so it too is not
13792 counted. The first occurrence of AUTH in a connection, or immediately
13793 following STARTTLS is not counted. Otherwise, all commands other than
13794 MAIL, RCPT, DATA, and QUIT are counted.
13797 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
13798 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
13799 check by setting this option. The default value makes it apply to all hosts. By
13800 changing the value, you can exclude any badly-behaved hosts that you have to
13805 .option smtp_accept_max_per_connection main integer 1000
13806 .cindex "SMTP incoming message count" "limiting"
13807 .cindex "limit" "messages per SMTP connection"
13808 The value of this option limits the number of MAIL commands that Exim is
13809 prepared to accept over a single SMTP connection, whether or not each command
13810 results in the transfer of a message. After the limit is reached, a 421
13811 response is given to subsequent MAIL commands. This limit is a safety
13812 precaution against a client that goes mad (incidents of this type have been
13816 .option smtp_accept_max_per_host main string&!! unset
13817 .cindex "limit" "SMTP connections from one host"
13818 .cindex "host" "limiting SMTP connections from"
13819 This option restricts the number of simultaneous IP connections from a single
13820 host (strictly, from a single IP address) to the Exim daemon. The option is
13821 expanded, to enable different limits to be applied to different hosts by
13822 reference to &$sender_host_address$&. Once the limit is reached, additional
13823 connection attempts from the same host are rejected with error code 421. The
13824 default value of zero imposes no limit. If this option is set, it is required
13825 that &%smtp_accept_max%& be non-zero.
13827 &*Warning*&: When setting this option you should not use any expansion
13828 constructions that take an appreciable amount of time. The expansion and test
13829 happen in the main daemon loop, in order to reject additional connections
13830 without forking additional processes (otherwise a denial-of-service attack
13831 could cause a vast number or processes to be created). While the daemon is
13832 doing this processing, it cannot accept any other incoming connections.
13836 .option smtp_accept_queue main integer 0
13837 .cindex "SMTP" "incoming connection count"
13838 .cindex "queueing incoming messages"
13839 .cindex "message" "queueing by SMTP connection count"
13840 If the number of simultaneous incoming SMTP calls handled via the listening
13841 daemon exceeds this value, messages received by SMTP are just placed on the
13842 queue; no delivery processes are started automatically. A value of zero implies
13843 no limit, and clearly any non-zero value is useful only if it is less than the
13844 &%smtp_accept_max%& value (unless that is zero). See also &%queue_only%&,
13845 &%queue_only_load%&, &%queue_smtp_domains%&, and the various &%-od%&&'x'&
13846 command line options.
13849 .option smtp_accept_queue_per_connection main integer 10
13850 .cindex "queueing incoming messages"
13851 .cindex "message" "queueing by message count"
13852 This option limits the number of delivery processes that Exim starts
13853 automatically when receiving messages via SMTP, whether via the daemon or by
13854 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
13855 and the number of messages received in a single SMTP session exceeds this
13856 number, subsequent messages are placed on the queue, but no delivery processes
13857 are started. This helps to limit the number of Exim processes when a server
13858 restarts after downtime and there is a lot of mail waiting for it on other
13859 systems. On large systems, the default should probably be increased, and on
13860 dial-in client systems it should probably be set to zero (that is, disabled).
13863 .option smtp_accept_reserve main integer 0
13864 .cindex "SMTP" "incoming call count"
13865 .cindex "host" "reserved"
13866 When &%smtp_accept_max%& is set greater than zero, this option specifies a
13867 number of SMTP connections that are reserved for connections from the hosts
13868 that are specified in &%smtp_reserve_hosts%&. The value set in
13869 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
13870 restricted to this number of connections; the option specifies a minimum number
13871 of connection slots for them, not a maximum. It is a guarantee that that group
13872 of hosts can always get at least &%smtp_accept_reserve%& connections.
13874 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
13875 set to 5, once there are 45 active connections (from any hosts), new
13876 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&.
13877 See also &%smtp_accept_max_per_host%&.
13880 .option smtp_active_hostname main string&!! unset
13881 .cindex "host" "name in SMTP responses"
13882 .cindex "SMTP" "host name in responses"
13883 .cindex "&$primary_hostname$&"
13884 This option is provided for multi-homed servers that want to masquerade as
13885 several different hosts. At the start of an SMTP connection, its value is
13886 expanded and used instead of the value of &$primary_hostname$& in SMTP
13887 responses. For example, it is used as domain name in the response to an
13888 incoming HELO or EHLO command.
13890 .cindex "&$smtp_active_hostname$&"
13891 It is also used in HELO commands for callout verification. The active hostname
13892 is placed in the &$smtp_active_hostname$& variable, which is saved with any
13893 messages that are received. It is therefore available for use in routers and
13894 transports when the message is later delivered.
13896 If this option is unset, or if its expansion is forced to fail, or if the
13897 expansion results in an empty string, the value of &$primary_hostname$& is
13898 used. Other expansion failures cause a message to be written to the main and
13899 panic logs, and the SMTP command receives a temporary error. Typically, the
13900 value of &%smtp_active_hostname%& depends on the incoming interface address.
13903 smtp_active_hostname = ${if eq{$interface_address}{10.0.0.1}\
13904 {cox.mydomain}{box.mydomain}}
13907 .option smtp_banner main string&!! "see below"
13908 .cindex "SMTP" "welcome banner"
13909 .cindex "banner for SMTP"
13910 .cindex "welcome banner for SMTP"
13911 .cindex "customizing" "SMTP banner"
13912 This string, which is expanded every time it is used, is output as the initial
13913 positive response to an SMTP connection. The default setting is:
13915 smtp_banner = $smtp_active_hostname ESMTP Exim \
13916 $version_number $tod_full
13918 Failure to expand the string causes a panic error. If you want to create a
13919 multiline response to the initial SMTP connection, use &"\n"& in the string at
13920 appropriate points, but not at the end. Note that the 220 code is not included
13921 in this string. Exim adds it automatically (several times in the case of a
13922 multiline response).
13925 .option smtp_check_spool_space main boolean true
13926 .cindex "checking disk space"
13927 .cindex "disk space" "checking"
13928 .cindex "spool directory" "checking space"
13929 When this option is set, if an incoming SMTP session encounters the SIZE
13930 option on a MAIL command, it checks that there is enough space in the
13931 spool directory's partition to accept a message of that size, while still
13932 leaving free the amount specified by &%check_spool_space%& (even if that value
13933 is zero). If there isn't enough space, a temporary error code is returned.
13936 .option smtp_connect_backlog main integer 20
13937 .cindex "connection backlog"
13938 .cindex "SMTP" "connection backlog"
13939 .cindex "backlog of connections"
13940 This option specifies a maximum number of waiting SMTP connections. Exim passes
13941 this value to the TCP/IP system when it sets up its listener. Once this number
13942 of connections are waiting for the daemon's attention, subsequent connection
13943 attempts are refused at the TCP/IP level. At least, that is what the manuals
13944 say; in some circumstances such connection attempts have been observed to time
13945 out instead. For large systems it is probably a good idea to increase the
13946 value (to 50, say). It also gives some protection against denial-of-service
13947 attacks by SYN flooding.
13950 .option smtp_enforce_sync main boolean true
13951 .cindex "SMTP" "synchronization checking"
13952 .cindex "synchronization checking in SMTP"
13953 The SMTP protocol specification requires the client to wait for a response from
13954 the server at certain points in the dialogue. Without PIPELINING these
13955 synchronization points are after every command; with PIPELINING they are
13956 fewer, but they still exist.
13958 Some spamming sites send out a complete set of SMTP commands without waiting
13959 for any response. Exim protects against this by rejecting a message if the
13960 client has sent further input when it should not have. The error response &"554
13961 SMTP synchronization error"& is sent, and the connection is dropped. Testing
13962 for this error cannot be perfect because of transmission delays (unexpected
13963 input may be on its way but not yet received when Exim checks). However, it
13964 does detect many instances.
13966 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
13967 If you want to disable the check selectively (for example, only for certain
13968 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
13969 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
13973 .option smtp_etrn_command main string&!! unset
13974 .cindex "ETRN" "command to be run"
13975 .cindex "&$domain$&"
13976 If this option is set, the given command is run whenever an SMTP ETRN
13977 command is received from a host that is permitted to issue such commands (see
13978 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
13979 are independently expanded. The expansion variable &$domain$& is set to the
13980 argument of the ETRN command, and no syntax checking is done on it. For
13983 smtp_etrn_command = /etc/etrn_command $domain \
13984 $sender_host_address
13986 A new process is created to run the command, but Exim does not wait for it to
13987 complete. Consequently, its status cannot be checked. If the command cannot be
13988 run, a line is written to the panic log, but the ETRN caller still receives
13989 a 250 success response. Exim is normally running under its own uid when
13990 receiving SMTP, so it is not possible for it to change the uid before running
13994 .option smtp_etrn_serialize main boolean true
13995 .cindex "ETRN" "serializing"
13996 When this option is set, it prevents the simultaneous execution of more than
13997 one identical command as a result of ETRN in an SMTP connection. See
13998 section &<<SECTETRN>>& for details.
14001 .option smtp_load_reserve main fixed-point unset
14002 .cindex "load average"
14003 If the system load average ever gets higher than this, incoming SMTP calls are
14004 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
14005 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
14006 the load is over the limit. The option has no effect on ancient operating
14007 systems on which Exim cannot determine the load average. See also
14008 &%deliver_queue_load_max%& and &%queue_only_load%&.
14012 .option smtp_max_synprot_errors main integer 3
14013 .cindex "SMTP" "limiting syntax and protocol errors"
14014 .cindex "limit" "SMTP syntax and protocol errors"
14015 Exim rejects SMTP commands that contain syntax or protocol errors. In
14016 particular, a syntactically invalid email address, as in this command:
14018 RCPT TO:<abc xyz@a.b.c>
14020 causes immediate rejection of the command, before any other tests are done.
14021 (The ACL cannot be run if there is no valid address to set up for it.) An
14022 example of a protocol error is receiving RCPT before MAIL. If there are
14023 too many syntax or protocol errors in one SMTP session, the connection is
14024 dropped. The limit is set by this option.
14026 .cindex "PIPELINING" "expected errors"
14027 When the PIPELINING extension to SMTP is in use, some protocol errors are
14028 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
14029 Exim assumes that PIPELINING will be used if it advertises it (see
14030 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
14031 not count towards the limit.
14035 .option smtp_max_unknown_commands main integer 3
14036 .cindex "SMTP" "limiting unknown commands"
14037 .cindex "limit" "unknown SMTP commands"
14038 If there are too many unrecognized commands in an incoming SMTP session, an
14039 Exim server drops the connection. This is a defence against some kinds of abuse
14042 into making connections to SMTP ports; in these circumstances, a number of
14043 non-SMTP command lines are sent first.
14047 .option smtp_ratelimit_hosts main "host list&!!" unset
14048 .cindex "SMTP" "rate limiting"
14049 .cindex "limit" "rate of message arrival"
14050 .cindex "RCPT" "rate limiting"
14051 Some sites find it helpful to be able to limit the rate at which certain hosts
14052 can send them messages, and the rate at which an individual message can specify
14055 Exim has two rate-limiting facilities. This section describes the older
14056 facility, which can limit rates within a single connection. The newer
14057 &%ratelimit%& ACL condition can limit rates across all connections. See section
14058 &<<SECTratelimiting>>& for details of the newer facility.
14060 When a host matches &%smtp_ratelimit_hosts%&, the values of
14061 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
14062 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
14063 respectively. Each option, if set, must contain a set of four comma-separated
14067 A threshold, before which there is no rate limiting.
14069 An initial time delay. Unlike other times in Exim, numbers with decimal
14070 fractional parts are allowed here.
14072 A factor by which to increase the delay each time.
14074 A maximum value for the delay. This should normally be less than 5 minutes,
14075 because after that time, the client is liable to timeout the SMTP command.
14078 For example, these settings have been used successfully at the site which
14079 first suggested this feature, for controlling mail from their customers:
14081 smtp_ratelimit_mail = 2,0.5s,1.05,4m
14082 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
14084 The first setting specifies delays that are applied to MAIL commands after
14085 two have been received over a single connection. The initial delay is 0.5
14086 seconds, increasing by a factor of 1.05 each time. The second setting applies
14087 delays to RCPT commands when more than four occur in a single message.
14090 .option smtp_ratelimit_mail main string unset
14091 See &%smtp_ratelimit_hosts%& above.
14094 .option smtp_ratelimit_rcpt main string unset
14095 See &%smtp_ratelimit_hosts%& above.
14098 .option smtp_receive_timeout main time 5m
14099 .cindex "timeout" "for SMTP input"
14100 .cindex "SMTP timeout" "input"
14101 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
14102 input, including batch SMTP. If a line of input (either an SMTP command or a
14103 data line) is not received within this time, the SMTP connection is dropped and
14104 the message is abandoned.
14105 A line is written to the log containing one of the following messages:
14107 SMTP command timeout on connection from...
14108 SMTP data timeout on connection from...
14110 The former means that Exim was expecting to read an SMTP command; the latter
14111 means that it was in the DATA phase, reading the contents of a message.
14114 .cindex "&%-os%& option"
14115 The value set by this option can be overridden by the
14116 &%-os%& command-line option. A setting of zero time disables the timeout, but
14117 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
14118 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
14119 timeout is controlled by &%receive_timeout%& and &%-or%&.
14122 .option smtp_reserve_hosts main "host list&!!" unset
14123 This option defines hosts for which SMTP connections are reserved; see
14124 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
14127 .option smtp_return_error_details main boolean false
14128 .cindex "SMTP" "details policy failures"
14129 .cindex "policy control rejection" "returning details"
14130 In the default state, Exim uses bland messages such as
14131 &"Administrative prohibition"& when it rejects SMTP commands for policy
14132 reasons. Many sysadmins like this because it gives away little information
14133 to spammers. However, some other syadmins who are applying strict checking
14134 policies want to give out much fuller information about failures. Setting
14135 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
14136 example, instead of &"Administrative prohibition"&, it might give:
14138 550-Rejected after DATA: '>' missing at end of address:
14139 550 failing address in "From" header is: <user@dom.ain
14142 .option spamd_address main string "see below"
14143 This option is available when Exim is compiled with the content-scanning
14144 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
14145 The default value is
14149 See section &<<SECTscanspamass>>& for more details.
14153 .option split_spool_directory main boolean false
14154 .cindex "multiple spool directories"
14155 .cindex "spool directory" "split"
14156 .cindex "directories" "multiple"
14157 If this option is set, it causes Exim to split its input directory into 62
14158 subdirectories, each with a single alphanumeric character as its name. The
14159 sixth character of the message id is used to allocate messages to
14160 subdirectories; this is the least significant base-62 digit of the time of
14161 arrival of the message.
14163 Splitting up the spool in this way may provide better performance on systems
14164 where there are long mail queues, by reducing the number of files in any one
14165 directory. The msglog directory is also split up in a similar way to the input
14166 directory; however, if &%preserve_message_logs%& is set, all old msglog files
14167 are still placed in the single directory &_msglog.OLD_&.
14169 It is not necessary to take any special action for existing messages when
14170 changing &%split_spool_directory%&. Exim notices messages that are in the
14171 &"wrong"& place, and continues to process them. If the option is turned off
14172 after a period of being on, the subdirectories will eventually empty and be
14173 automatically deleted.
14175 When &%split_spool_directory%& is set, the behaviour of queue runner processes
14176 changes. Instead of creating a list of all messages in the queue, and then
14177 trying to deliver each one in turn, it constructs a list of those in one
14178 sub-directory and tries to deliver them, before moving on to the next
14179 sub-directory. The sub-directories are processed in a random order. This
14180 spreads out the scanning of the input directories, and uses less memory. It is
14181 particularly beneficial when there are lots of messages on the queue. However,
14182 if &%queue_run_in_order%& is set, none of this new processing happens. The
14183 entire queue has to be scanned and sorted before any deliveries can start.
14186 .option spool_directory main string&!! "set at compile time"
14187 .cindex "spool directory" "path to"
14188 This defines the directory in which Exim keeps its spool, that is, the messages
14189 it is waiting to deliver. The default value is taken from the compile-time
14190 configuration setting, if there is one. If not, this option must be set. The
14191 string is expanded, so it can contain, for example, a reference to
14192 &$primary_hostname$&.
14194 If the spool directory name is fixed on your installation, it is recommended
14195 that you set it at build time rather than from this option, particularly if the
14196 log files are being written to the spool directory (see &%log_file_path%&).
14197 Otherwise log files cannot be used for errors that are detected early on, such
14198 as failures in the configuration file.
14200 By using this option to override the compiled-in path, it is possible to run
14201 tests of Exim without using the standard spool.
14203 .option sqlite_lock_timeout main time 5s
14204 .cindex "sqlite" "lock timeout"
14205 This option controls the timeout that the &(sqlite)& lookup uses when trying to
14206 access an SQLite database. See section &<<SECTsqlite>>& for more details.
14208 .option strip_excess_angle_brackets main boolean false
14209 .cindex "angle brackets" "excess"
14210 If this option is set, redundant pairs of angle brackets round &"route-addr"&
14211 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
14212 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
14213 passed on to another MTA, the excess angle brackets are not passed on. If this
14214 option is not set, multiple pairs of angle brackets cause a syntax error.
14217 .option strip_trailing_dot main boolean false
14218 .cindex "trailing dot on domain"
14219 .cindex "dot" "trailing on domain"
14220 If this option is set, a trailing dot at the end of a domain in an address is
14221 ignored. If this is in the envelope and the message is passed on to another
14222 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
14223 domain causes a syntax error.
14224 However, addresses in header lines are checked only when an ACL requests header
14228 .option syslog_duplication main boolean true
14229 .cindex "syslog" "duplicate log lines; suppressing"
14230 When Exim is logging to syslog, it writes the log lines for its three
14231 separate logs at different syslog priorities so that they can in principle
14232 be separated on the logging hosts. Some installations do not require this
14233 separation, and in those cases, the duplication of certain log lines is a
14234 nuisance. If &%syslog_duplication%& is set false, only one copy of any
14235 particular log line is written to syslog. For lines that normally go to
14236 both the main log and the reject log, the reject log version (possibly
14237 containing message header lines) is written, at LOG_NOTICE priority.
14238 Lines that normally go to both the main and the panic log are written at
14239 the LOG_ALERT priority.
14242 .option syslog_facility main string unset
14243 .cindex "syslog" "facility; setting"
14244 This option sets the syslog &"facility"& name, used when Exim is logging to
14245 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
14246 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
14247 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
14248 details of Exim's logging.
14252 .option syslog_processname main string &`exim`&
14253 .cindex "syslog" "process name; setting"
14254 This option sets the syslog &"ident"& name, used when Exim is logging to
14255 syslog. The value must be no longer than 32 characters. See chapter
14256 &<<CHAPlog>>& for details of Exim's logging.
14260 .option syslog_timestamp main boolean true
14261 .cindex "syslog" "timestamps"
14262 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
14263 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
14264 details of Exim's logging.
14267 .option system_filter main string&!! unset
14268 .cindex "filter" "system filter"
14269 .cindex "system filter" "specifying"
14270 .cindex "Sieve filter" "not available for system filter"
14271 This option specifies an Exim filter file that is applied to all messages at
14272 the start of each delivery attempt, before any routing is done. System filters
14273 must be Exim filters; they cannot be Sieve filters. If the system filter
14274 generates any deliveries to files or pipes, or any new mail messages, the
14275 appropriate &%system_filter_..._transport%& option(s) must be set, to define
14276 which transports are to be used. Details of this facility are given in chapter
14277 &<<CHAPsystemfilter>>&.
14280 .option system_filter_directory_transport main string&!! unset
14281 .cindex "&$address_file$&"
14282 This sets the name of the transport driver that is to be used when the
14283 &%save%& command in a system message filter specifies a path ending in &"/"&,
14284 implying delivery of each message into a separate file in some directory.
14285 During the delivery, the variable &$address_file$& contains the path name.
14288 .option system_filter_file_transport main string&!! unset
14289 .cindex "file" "transport for system filter"
14290 This sets the name of the transport driver that is to be used when the &%save%&
14291 command in a system message filter specifies a path not ending in &"/"&. During
14292 the delivery, the variable &$address_file$& contains the path name.
14294 .option system_filter_group main string unset
14295 .cindex "gid (group id)" "system filter"
14296 This option is used only when &%system_filter_user%& is also set. It sets the
14297 gid under which the system filter is run, overriding any gid that is associated
14298 with the user. The value may be numerical or symbolic.
14300 .option system_filter_pipe_transport main string&!! unset
14301 .cindex "&(pipe)& transport" "for system filter"
14302 .cindex "&$address_pipe$&"
14303 This specifies the transport driver that is to be used when a &%pipe%& command
14304 is used in a system filter. During the delivery, the variable &$address_pipe$&
14305 contains the pipe command.
14308 .option system_filter_reply_transport main string&!! unset
14309 .cindex "&(autoreply)& transport" "for system filter"
14310 This specifies the transport driver that is to be used when a &%mail%& command
14311 is used in a system filter.
14313 .option system_filter_user main string unset
14314 .cindex "uid (user id)" "system filter"
14315 If this option is not set, the system filter is run in the main Exim delivery
14316 process, as root. When the option is set, the system filter runs in a separate
14317 process, as the given user. Unless the string consists entirely of digits, it
14318 is looked up in the password data. Failure to find the named user causes a
14319 configuration error. The gid is either taken from the password data, or
14320 specified by &%system_filter_group%&. When the uid is specified numerically,
14321 &%system_filter_group%& is required to be set.
14323 If the system filter generates any pipe, file, or reply deliveries, the uid
14324 under which the filter is run is used when transporting them, unless a
14325 transport option overrides. Normally you should set &%system_filter_user%& if
14326 your system filter generates these kinds of delivery.
14329 .option tcp_nodelay main boolean true
14330 .cindex "daemon" "TCP_NODELAY on sockets"
14331 .cindex "Nagle algorithm"
14332 .cindex "TCP_NODELAY on listening sockets"
14333 If this option is set false, it stops the Exim daemon setting the
14334 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
14335 turns off the &"Nagle algorithm"&, which is a way of improving network
14336 performance in interactive (character-by-character) situations. Turning it off
14337 should improve Exim's performance a bit, so that is what happens by default.
14338 However, it appears that some broken clients cannot cope, and time out. Hence
14339 this option. It affects only those sockets that are set up for listening by the
14340 daemon. Sockets created by the smtp transport for delivering mail always set
14344 .option timeout_frozen_after main time 0s
14345 .cindex "frozen messages" "timing out"
14346 .cindex "timeout" "frozen messages"
14347 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
14348 message of any kind that has been on the queue for longer than the given
14349 time is automatically cancelled at the next queue run. If it is a bounce
14350 message, it is just discarded; otherwise, a bounce is sent to the sender, in a
14351 similar manner to cancellation by the &%-Mg%& command line option. If you want
14352 to timeout frozen bounce messages earlier than other kinds of frozen message,
14353 see &%ignore_bounce_errors_after%&.
14356 .option timezone main string unset
14357 .cindex "timezone" "setting"
14358 The value of &%timezone%& is used to set the environment variable TZ while
14359 running Exim (if it is different on entry). This ensures that all timestamps
14360 created by Exim are in the required timezone. If you want all your timestamps
14361 to be in UTC (aka GMT) you should set
14365 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
14366 or, if that is not set, from the value of the TZ environment variable when Exim
14367 is built. If &%timezone%& is set to the empty string, either at build or run
14368 time, any existing TZ variable is removed from the environment when Exim
14369 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
14370 unfortunately not all, operating systems.
14373 .option tls_advertise_hosts main "host list&!!" unset
14374 .cindex "TLS" "advertising"
14375 .cindex "encryption" "on SMTP connection"
14376 .cindex "SMTP" "encrypted connection"
14377 When Exim is built with support for TLS encrypted connections, the availability
14378 of the STARTTLS command to set up an encrypted session is advertised in
14379 response to EHLO only to those client hosts that match this option. See
14380 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
14383 .option tls_certificate main string&!! unset
14384 .cindex "TLS" "server certificate; location of"
14385 .cindex "certificate for server" "location of"
14386 The value of this option is expanded, and must then be the absolute path to a
14387 file which contains the server's certificates. The server's private key is also
14388 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
14389 &<<CHAPTLS>>& for further details.
14391 &*Note*&: The certificates defined by this option are used only when Exim is
14392 receiving incoming messages as a server. If you want to supply certificates for
14393 use when sending messages as a client, you must set the &%tls_certificate%&
14394 option in the relevant &(smtp)& transport.
14397 .option tls_crl main string&!! unset
14398 .cindex "TLS" "server certificate revocation list"
14399 .cindex "certificate" "revocation list for server"
14400 This option specifies a certificate revocation list. The expanded value must
14401 be the name of a file that contains a CRL in PEM format.
14404 .option tls_dhparam main string&!! unset
14405 .cindex "TLS" "D-H parameters for server"
14406 The value of this option is expanded, and must then be the absolute path to
14407 a file which contains the server's DH parameter values.
14408 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
14409 ignored. See section &<<SECTopenvsgnu>>& for further details.
14412 .option tls_on_connect_ports main "string list" unset
14413 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
14414 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
14415 set up without waiting for the client to issue a STARTTLS command. For
14416 further details, see section &<<SECTsupobssmt>>&.
14420 .option tls_privatekey main string&!! unset
14421 .cindex "TLS" "server private key; location of"
14423 The value of this option is expanded, and must then be the absolute path to a
14424 file which contains the server's private key. If this option is unset, or if
14425 the expansion is forced to fail, or the result is an empty string, the private
14426 key is assumed to be in the same file as the server's certificates. See chapter
14427 &<<CHAPTLS>>& for further details.
14431 .option tls_remember_esmtp main boolean false
14432 .cindex "TLS" "esmtp state; remembering"
14433 .cindex "TLS" "broken clients"
14434 If this option is set true, Exim violates the RFCs by remembering that it is in
14435 &"esmtp"& state after successfully negotiating a TLS session. This provides
14436 support for broken clients that fail to send a new EHLO after starting a
14440 .option tls_require_ciphers main string&!! unset
14441 .cindex "TLS" "requiring specific ciphers"
14442 .cindex "cipher" "requiring specific"
14443 This option controls which ciphers can be used for incoming TLS connections.
14444 The &(smtp)& transport has an option of the same name for controlling outgoing
14445 connections. This option is expanded for each connection, so can be varied for
14446 different clients if required. The value of this option must be a list of
14447 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
14448 in somewhat different ways. If GnuTLS is being used, the client controls the
14449 preference order of the available ciphers. Details are given in sections
14450 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
14453 .option tls_try_verify_hosts main "host list&!!" unset
14454 .cindex "TLS" "client certificate verification"
14455 .cindex "certificate" "verification of client"
14456 See &%tls_verify_hosts%& below.
14459 .option tls_verify_certificates main string&!! unset
14460 .cindex "TLS" "client certificate verification"
14461 .cindex "certificate" "verification of client"
14462 The value of this option is expanded, and must then be the absolute path to
14463 a file containing permitted certificates for clients that
14464 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
14465 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
14466 directory containing certificate files. This does not work with GnuTLS; the
14467 option must be set to the name of a single file if you are using GnuTLS.
14470 .option tls_verify_hosts main "host list&!!" unset
14471 .cindex "TLS" "client certificate verification"
14472 .cindex "certificate" "verification of client"
14473 This option, along with &%tls_try_verify_hosts%&, controls the checking of
14474 certificates from clients.
14475 The expected certificates are defined by &%tls_verify_certificates%&, which
14476 must be set. A configuration error occurs if either &%tls_verify_hosts%& or
14477 &%tls_try_verify_hosts%& is set and &%tls_verify_certificates%& is not set.
14479 Any client that matches &%tls_verify_hosts%& is constrained by
14480 &%tls_verify_certificates%&. The client must present one of the listed
14481 certificates. If it does not, the connection is aborted.
14483 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
14484 matches this option (but not &%tls_verify_hosts%&), Exim requests a
14485 certificate and checks it against &%tls_verify_certificates%&, but does not
14486 abort the connection if there is no certificate or if it does not match. This
14487 state can be detected in an ACL, which makes it possible to implement policies
14488 such as &"accept for relay only if a verified certificate has been received,
14489 but accept for local delivery if encrypted, even without a verified
14492 Client hosts that match neither of these lists are not asked to present
14496 .option trusted_groups main "string list&!!" unset
14497 .cindex "trusted group"
14498 .cindex "group" "trusted"
14499 This option is expanded just once, at the start of Exim's processing. If this
14500 option is set, any process that is running in one of the listed groups, or
14501 which has one of them as a supplementary group, is trusted. The groups can be
14502 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
14503 details of what trusted callers are permitted to do. If neither
14504 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
14507 .option trusted_users main "string list&!!" unset
14508 .cindex "trusted user"
14509 .cindex "user" "trusted"
14510 This option is expanded just once, at the start of Exim's processing. If this
14511 option is set, any process that is running as one of the listed users is
14512 trusted. The users can be specified numerically or by name. See section
14513 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
14514 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
14515 Exim user are trusted.
14517 .option unknown_login main string&!! unset
14518 .cindex "uid (user id)" "unknown caller"
14519 .cindex "&$caller_uid$&"
14520 This is a specialized feature for use in unusual configurations. By default, if
14521 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
14522 gives up. The &%unknown_login%& option can be used to set a login name to be
14523 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
14524 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
14525 is used for the user's real name (gecos field), unless this has been set by the
14528 .option unknown_username main string unset
14529 See &%unknown_login%&.
14531 .option untrusted_set_sender main "address list&!!" unset
14532 .cindex "trusted user"
14533 .cindex "sender" "setting by untrusted user"
14534 .cindex "untrusted user" "setting sender"
14535 .cindex "user" "untrusted setting sender"
14536 .cindex "envelope sender"
14537 When an untrusted user submits a message to Exim using the standard input, Exim
14538 normally creates an envelope sender address from the user's login and the
14539 default qualification domain. Data from the &%-f%& option (for setting envelope
14540 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
14541 is used) is ignored.
14543 However, untrusted users are permitted to set an empty envelope sender address,
14544 to declare that a message should never generate any bounces. For example:
14546 exim -f '<>' user@domain.example
14548 .cindex "&$sender_ident$&"
14549 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
14550 other envelope sender addresses in a controlled way. When it is set, untrusted
14551 users are allowed to set envelope sender addresses that match any of the
14552 patterns in the list. Like all address lists, the string is expanded. The
14553 identity of the user is in &$sender_ident$&, so you can, for example, restrict
14554 users to setting senders that start with their login ids
14555 followed by a hyphen
14556 by a setting like this:
14558 untrusted_set_sender = ^$sender_ident-
14560 If you want to allow untrusted users to set envelope sender addresses without
14561 restriction, you can use
14563 untrusted_set_sender = *
14565 The &%untrusted_set_sender%& option applies to all forms of local input, but
14566 only to the setting of the envelope sender. It does not permit untrusted users
14567 to use the other options which trusted user can use to override message
14568 parameters. Furthermore, it does not stop Exim from removing an existing
14569 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
14570 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
14571 overriding these actions. The handling of the &'Sender:'& header is also
14572 described in section &<<SECTthesenhea>>&.
14574 The log line for a message's arrival shows the envelope sender following
14575 &"<="&. For local messages, the user's login always follows, after &"U="&. In
14576 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
14577 envelope sender address, the user's login is shown in parentheses after the
14581 .option uucp_from_pattern main string "see below"
14582 .cindex "&""From""& line"
14583 .cindex "UUCP" "&""From""& line"
14584 Some applications that pass messages to an MTA via a command line interface use
14585 an initial line starting with &"From&~"& to pass the envelope sender. In
14586 particular, this is used by UUCP software. Exim recognizes such a line by means
14587 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
14588 matches, the sender address is constructed by expanding the contents of
14589 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
14590 default pattern recognizes lines in the following two forms:
14592 From ph10 Fri Jan 5 12:35 GMT 1996
14593 From ph10 Fri, 7 Jan 97 14:00:00 GMT
14595 The pattern can be seen by running
14597 exim -bP uucp_from_pattern
14599 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
14600 year in the second case. The first word after &"From&~"& is matched in the
14601 regular expression by a parenthesized subpattern. The default value for
14602 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
14603 (&"ph10"& in the example above) as the message's sender. See also
14604 &%ignore_fromline_hosts%&.
14607 .option uucp_from_sender main string&!! &`$1`&
14608 See &%uucp_from_pattern%& above.
14611 .option warn_message_file main string unset
14612 .cindex "warning of delay" "customizing the message"
14613 .cindex "customizing" "warning message"
14614 This option defines a template file containing paragraphs of text to be used
14615 for constructing the warning message which is sent by Exim when a message has
14616 been on the queue for a specified amount of time, as specified by
14617 &%delay_warning%&. Details of the file's contents are given in chapter
14618 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
14621 .option write_rejectlog main boolean true
14622 .cindex "reject log" "disabling"
14623 If this option is set false, Exim no longer writes anything to the reject log.
14624 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
14625 .ecindex IIDconfima
14626 .ecindex IIDmaiconf
14631 . ////////////////////////////////////////////////////////////////////////////
14632 . ////////////////////////////////////////////////////////////////////////////
14634 .chapter "Generic options for routers" "CHAProutergeneric"
14635 .scindex IIDgenoprou1 "options" "generic; for routers"
14636 .scindex IIDgenoprou2 "generic options" "router"
14637 This chapter describes the generic options that apply to all routers.
14638 Those that are preconditions are marked with ‡ in the &"use"& field.
14640 For a general description of how a router operates, see sections
14641 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
14642 which the preconditions are tested. The order of expansion of the options that
14643 provide data for a transport is: &%errors_to%&, &%headers_add%&,
14644 &%headers_remove%&, &%transport%&.
14648 .option address_data routers string&!! unset
14649 .cindex "router" "data attached to address"
14650 The string is expanded just before the router is run, that is, after all the
14651 precondition tests have succeeded. If the expansion is forced to fail, the
14652 router declines, the value of &%address_data%& remains unchanged, and the
14653 &%more%& option controls what happens next. Other expansion failures cause
14654 delivery of the address to be deferred.
14656 .cindex "&$address_data$&"
14657 When the expansion succeeds, the value is retained with the address, and can be
14658 accessed using the variable &$address_data$& in the current router, subsequent
14659 routers, and the eventual transport.
14661 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
14662 that runs a user's filter file, the contents of &$address_data$& are accessible
14663 in the filter. This is not normally a problem, because such data is usually
14664 either not confidential or it &"belongs"& to the current user, but if you do
14665 put confidential data into &$address_data$& you need to remember this point.
14667 Even if the router declines or passes, the value of &$address_data$& remains
14668 with the address, though it can be changed by another &%address_data%& setting
14669 on a subsequent router. If a router generates child addresses, the value of
14670 &$address_data$& propagates to them. This also applies to the special kind of
14671 &"child"& that is generated by a router with the &%unseen%& option.
14673 The idea of &%address_data%& is that you can use it to look up a lot of data
14674 for the address once, and then pick out parts of the data later. For example,
14675 you could use a single LDAP lookup to return a string of the form
14677 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
14679 In the transport you could pick out the mailbox by a setting such as
14681 file = ${extract{mailbox}{$address_data}}
14683 This makes the configuration file less messy, and also reduces the number of
14684 lookups (though Exim does cache lookups).
14686 The &%address_data%& facility is also useful as a means of passing information
14687 from one router to another, and from a router to a transport. In addition, if
14689 .cindex "&$sender_address_data$&"
14690 .cindex "&$address_data$&"
14691 When &$address_data$& is set by a router when verifying a recipient address
14692 from an ACL, it remains available for use in the rest of the ACL statement.
14693 After verifying a sender, the value is transferred to &$sender_address_data$&.
14698 .option address_test routers&!? boolean true
14699 .cindex "&%-bt%& option"
14700 .cindex "router" "skipping when address testing"
14701 If this option is set false, the router is skipped when routing is being tested
14702 by means of the &%-bt%& command line option. This can be a convenience when
14703 your first router sends messages to an external scanner, because it saves you
14704 having to set the &"already scanned"& indicator when testing real address
14709 .option cannot_route_message routers string&!! unset
14710 .cindex "router" "customizing &""cannot route""& message"
14711 .cindex "customizing" "&""cannot route""& message"
14712 This option specifies a text message that is used when an address cannot be
14713 routed because Exim has run out of routers. The default message is
14714 &"Unrouteable address"&. This option is useful only on routers that have
14715 &%more%& set false, or on the very last router in a configuration, because the
14716 value that is used is taken from the last router that is considered. This
14717 includes a router that is skipped because its preconditions are not met, as
14718 well as a router that declines. For example, using the default configuration,
14721 cannot_route_message = Remote domain not found in DNS
14723 on the first router, which is a &(dnslookup)& router with &%more%& set false,
14726 cannot_route_message = Unknown local user
14728 on the final router that checks for local users. If string expansion fails for
14729 this option, the default message is used. Unless the expansion failure was
14730 explicitly forced, a message about the failure is written to the main and panic
14731 logs, in addition to the normal message about the routing failure.
14734 .option caseful_local_part routers boolean false
14735 .cindex "case of local parts"
14736 .cindex "router" "case of local parts"
14737 By default, routers handle the local parts of addresses in a case-insensitive
14738 manner, though the actual case is preserved for transmission with the message.
14739 If you want the case of letters to be significant in a router, you must set
14740 this option true. For individual router options that contain address or local
14741 part lists (for example, &%local_parts%&), case-sensitive matching can be
14742 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
14745 .cindex "&$local_part$&"
14746 .cindex "&$original_local_part$&"
14747 .cindex "&$parent_local_part$&"
14748 The value of the &$local_part$& variable is forced to lower case while a
14749 router is running unless &%caseful_local_part%& is set. When a router assigns
14750 an address to a transport, the value of &$local_part$& when the transport runs
14751 is the same as it was in the router. Similarly, when a router generates child
14752 addresses by aliasing or forwarding, the values of &$original_local_part$&
14753 and &$parent_local_part$& are those that were used by the redirecting router.
14755 This option applies to the processing of an address by a router. When a
14756 recipient address is being processed in an ACL, there is a separate &%control%&
14757 modifier that can be used to specify case-sensitive processing within the ACL
14758 (see section &<<SECTcontrols>>&).
14762 .option check_local_user routers&!? boolean false
14763 .cindex "local user" "checking in router"
14764 .cindex "router" "checking for local user"
14765 .cindex "&_/etc/passwd_&"
14767 When this option is true, Exim checks that the local part of the recipient
14768 address (with affixes removed if relevant) is the name of an account on the
14769 local system. The check is done by calling the &[getpwnam()]& function rather
14770 than trying to read &_/etc/passwd_& directly. This means that other methods of
14771 holding password data (such as NIS) are supported. If the local part is a local
14772 user, &$home$& is set from the password data, and can be tested in other
14773 preconditions that are evaluated after this one (the order of evaluation is
14774 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
14775 overridden by &%router_home_directory%&. If the local part is not a local user,
14776 the router is skipped.
14778 If you want to check that the local part is either the name of a local user
14779 or matches something else, you cannot combine &%check_local_user%& with a
14780 setting of &%local_parts%&, because that specifies the logical &'and'& of the
14781 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
14782 setting to achieve this. For example:
14784 local_parts = passwd;$local_part : lsearch;/etc/other/users
14786 Note, however, that the side effects of &%check_local_user%& (such as setting
14787 up a home directory) do not occur when a &(passwd)& lookup is used in a
14788 &%local_parts%& (or any other) precondition.
14792 .option condition routers&!? string&!! unset
14793 .cindex "router" "customized precondition"
14794 This option specifies a general precondition test that has to succeed for the
14795 router to be called. The &%condition%& option is the last precondition to be
14796 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
14797 result is a forced failure, or an empty string, or one of the strings &"0"& or
14798 &"no"& or &"false"& (checked without regard to the case of the letters), the
14799 router is skipped, and the address is offered to the next one.
14801 If the result is any other value, the router is run (as this is the last
14802 precondition to be evaluated, all the other preconditions must be true).
14804 The &%condition%& option provides a means of applying custom conditions to the
14805 running of routers. Note that in the case of a simple conditional expansion,
14806 the default expansion values are exactly what is wanted. For example:
14808 condition = ${if >{$message_age}{600}}
14810 Because of the default behaviour of the string expansion, this is equivalent to
14812 condition = ${if >{$message_age}{600}{true}{}}
14814 If the expansion fails (other than forced failure) delivery is deferred. Some
14815 of the other precondition options are common special cases that could in fact
14816 be specified using &%condition%&.
14820 .option debug_print routers string&!! unset
14821 .cindex "testing" "variables in drivers"
14822 If this option is set and debugging is enabled (see the &%-d%& command line
14823 option), the string is expanded and included in the debugging output.
14824 If expansion of the string fails, the error message is written to the debugging
14825 output, and Exim carries on processing.
14826 This option is provided to help with checking out the values of variables and
14827 so on when debugging router configurations. For example, if a &%condition%&
14828 option appears not to be working, &%debug_print%& can be used to output the
14829 variables it references. The output happens after checks for &%domains%&,
14830 &%local_parts%&, and &%check_local_user%& but before any other preconditions
14831 are tested. A newline is added to the text if it does not end with one.
14835 .option disable_logging routers boolean false
14836 If this option is set true, nothing is logged for any routing errors
14837 or for any deliveries caused by this router. You should not set this option
14838 unless you really, really know what you are doing. See also the generic
14839 transport option of the same name.
14842 .option domains routers&!? "domain list&!!" unset
14843 .cindex "router" "restricting to specific domains"
14844 .cindex "&$domain_data$&"
14845 If this option is set, the router is skipped unless the current domain matches
14846 the list. If the match is achieved by means of a file lookup, the data that the
14847 lookup returned for the domain is placed in &$domain_data$& for use in string
14848 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
14849 a list of the order in which preconditions are evaluated.
14853 .option driver routers string unset
14854 This option must always be set. It specifies which of the available routers is
14859 .option errors_to routers string&!! unset
14860 .cindex "envelope sender"
14861 .cindex "router" "changing address for errors"
14862 If a router successfully handles an address, it may assign the address to a
14863 transport for delivery or it may generate child addresses. In both cases, if
14864 there is a delivery problem during later processing, the resulting bounce
14865 message is sent to the address that results from expanding this string,
14866 provided that the address verifies successfully. The &%errors_to%& option is
14867 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
14869 The &%errors_to%& setting associated with an address can be overridden if it
14870 subsequently passes through other routers that have their own &%errors_to%&
14871 settings, or if the message is delivered by a transport with a &%return_path%&
14874 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
14875 the expansion fails to verify, the errors address associated with the incoming
14876 address is used. At top level, this is the envelope sender. A non-forced
14877 expansion failure causes delivery to be deferred.
14879 If an address for which &%errors_to%& has been set ends up being delivered over
14880 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
14881 any bounces that are generated by other MTAs on the delivery route are also
14882 sent there. You can set &%errors_to%& to the empty string by either of these
14888 An expansion item that yields an empty string has the same effect. If you do
14889 this, a locally detected delivery error for addresses processed by this router
14890 no longer gives rise to a bounce message; the error is discarded. If the
14891 address is delivered to a remote host, the return path is set to &`<>`&, unless
14892 overridden by the &%return_path%& option on the transport.
14894 .cindex "&$address_data$&"
14895 If for some reason you want to discard local errors, but use a non-empty
14896 MAIL command for remote delivery, you can preserve the original return
14897 path in &$address_data$& in the router, and reinstate it in the transport by
14898 setting &%return_path%&.
14900 The most common use of &%errors_to%& is to direct mailing list bounces to the
14901 manager of the list, as described in section &<<SECTmailinglists>>&, or to
14902 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
14906 .option expn routers&!? boolean true
14907 .cindex "address" "testing"
14908 .cindex "testing" "addresses"
14909 .cindex "EXPN" "router skipping"
14910 .cindex "router" "skipping for EXPN"
14911 If this option is turned off, the router is skipped when testing an address
14912 as a result of processing an SMTP EXPN command. You might, for example,
14913 want to turn it off on a router for users' &_.forward_& files, while leaving it
14914 on for the system alias file.
14915 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
14918 The use of the SMTP EXPN command is controlled by an ACL (see chapter
14919 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
14920 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
14924 .option fail_verify routers boolean false
14925 .cindex "router" "forcing verification failure"
14926 Setting this option has the effect of setting both &%fail_verify_sender%& and
14927 &%fail_verify_recipient%& to the same value.
14931 .option fail_verify_recipient routers boolean false
14932 If this option is true and an address is accepted by this router when
14933 verifying a recipient, verification fails.
14937 .option fail_verify_sender routers boolean false
14938 If this option is true and an address is accepted by this router when
14939 verifying a sender, verification fails.
14943 .option fallback_hosts routers "string list" unset
14944 .cindex "router" "fallback hosts"
14945 .cindex "fallback" "hosts specified on router"
14946 String expansion is not applied to this option. The argument must be a
14947 colon-separated list of host names or IP addresses. The list separator can be
14948 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
14949 each name or address. In fact, the format of each item is exactly the same as
14950 defined for the list of hosts in a &(manualroute)& router (see section
14951 &<<SECTformatonehostitem>>&).
14953 If a router queues an address for a remote transport, this host list is
14954 associated with the address, and used instead of the transport's fallback host
14955 list. If &%hosts_randomize%& is set on the transport, the order of the list is
14956 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
14957 transport for further details.
14960 .option group routers string&!! "see below"
14961 .cindex "gid (group id)" "local delivery"
14962 .cindex "local transports" "uid and gid"
14963 .cindex "transport" "local"
14964 .cindex "router" "setting group"
14965 When a router queues an address for a transport, and the transport does not
14966 specify a group, the group given here is used when running the delivery
14968 The group may be specified numerically or by name. If expansion fails, the
14969 error is logged and delivery is deferred.
14970 The default is unset, unless &%check_local_user%& is set, when the default
14971 is taken from the password information. See also &%initgroups%& and &%user%&
14972 and the discussion in chapter &<<CHAPenvironment>>&.
14976 .option headers_add routers string&!! unset
14977 .cindex "header lines" "adding"
14978 .cindex "router" "adding header lines"
14979 This option specifies a string of text that is expanded at routing time, and
14980 associated with any addresses that are accepted by the router. However, this
14981 option has no effect when an address is just being verified. The way in which
14982 the text is used to add header lines at transport time is described in section
14983 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
14984 message is in the process of being transported. This means that references to
14985 header lines in string expansions in the transport's configuration do not
14986 &"see"& the added header lines.
14988 The &%headers_add%& option is expanded after &%errors_to%&, but before
14989 &%headers_remove%& and &%transport%&. If the expanded string is empty, or if
14990 the expansion is forced to fail, the option has no effect. Other expansion
14991 failures are treated as configuration errors.
14993 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
14994 router that has the &%one_time%& option set.
14996 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
14997 additions are deleted when the address is passed on to subsequent routers.
15001 .option headers_remove routers string&!! unset
15002 .cindex "header lines" "removing"
15003 .cindex "router" "removing header lines"
15004 This option specifies a string of text that is expanded at routing time, and
15005 associated with any addresses that are accepted by the router. However, this
15006 option has no effect when an address is just being verified. The way in which
15007 the text is used to remove header lines at transport time is described in
15008 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
15009 the message is in the process of being transported. This means that references
15010 to header lines in string expansions in the transport's configuration still
15011 &"see"& the original header lines.
15013 The &%headers_remove%& option is expanded after &%errors_to%& and
15014 &%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
15015 the option has no effect. Other expansion failures are treated as configuration
15018 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
15019 router that has the &%one_time%& option set.
15021 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15022 removal requests are deleted when the address is passed on to subsequent
15026 .option ignore_target_hosts routers "host list&!!" unset
15027 .cindex "IP address" "discarding"
15028 .cindex "router" "discarding IP addresses"
15029 Although this option is a host list, it should normally contain IP address
15030 entries rather than names. If any host that is looked up by the router has an
15031 IP address that matches an item in this list, Exim behaves as if that IP
15032 address did not exist. This option allows you to cope with rogue DNS entries
15035 remote.domain.example. A 127.0.0.1
15039 ignore_target_hosts = 127.0.0.1
15041 on the relevant router. If all the hosts found by a &(dnslookup)& router are
15042 discarded in this way, the router declines. In a conventional configuration, an
15043 attempt to mail to such a domain would normally provoke the &"unrouteable
15044 domain"& error, and an attempt to verify an address in the domain would fail.
15045 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
15046 router declines if presented with one of the listed addresses.
15048 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
15049 means of the first or the second of the following settings, respectively:
15051 ignore_target_hosts = 0.0.0.0/0
15052 ignore_target_hosts = <; 0::0/0
15054 The pattern in the first line matches all IPv4 addresses, whereas the pattern
15055 in the second line matches all IPv6 addresses.
15057 This option may also be useful for ignoring link-local and site-local IPv6
15058 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
15059 is expanded before use as a list, it is possible to make it dependent on the
15060 domain that is being routed.
15062 .cindex "&$host_address$&"
15063 During its expansion, &$host_address$& is set to the IP address that is being
15066 .option initgroups routers boolean false
15067 .cindex "additional groups"
15068 .cindex "groups" "additional"
15069 .cindex "local transports" "uid and gid"
15070 .cindex "transport" "local"
15071 If the router queues an address for a transport, and this option is true, and
15072 the uid supplied by the router is not overridden by the transport, the
15073 &[initgroups()]& function is called when running the transport to ensure that
15074 any additional groups associated with the uid are set up. See also &%group%&
15075 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
15079 .option local_part_prefix routers&!? "string list" unset
15080 .cindex "router" "prefix for local part"
15081 .cindex "prefix" "for local part; used in router"
15082 If this option is set, the router is skipped unless the local part starts with
15083 one of the given strings, or &%local_part_prefix_optional%& is true. See
15084 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
15087 The list is scanned from left to right, and the first prefix that matches is
15088 used. A limited form of wildcard is available; if the prefix begins with an
15089 asterisk, it matches the longest possible sequence of arbitrary characters at
15090 the start of the local part. An asterisk should therefore always be followed by
15091 some character that does not occur in normal local parts.
15092 .cindex "multiple mailboxes"
15093 .cindex "mailbox" "multiple"
15094 Wildcarding can be used to set up multiple user mailboxes, as described in
15095 section &<<SECTmulbox>>&.
15097 .cindex "&$local_part$&"
15098 .cindex "&$local_part_prefix$&"
15099 During the testing of the &%local_parts%& option, and while the router is
15100 running, the prefix is removed from the local part, and is available in the
15101 expansion variable &$local_part_prefix$&. When a message is being delivered, if
15102 the router accepts the address, this remains true during subsequent delivery by
15103 a transport. In particular, the local part that is transmitted in the RCPT
15104 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
15105 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
15106 the relevant transport.
15108 When an address is being verified, &%local_part_prefix%& affects only the
15109 behaviour of the router. If the callout feature of verification is in use, this
15110 means that the full address, including the prefix, will be used during the
15113 The prefix facility is commonly used to handle local parts of the form
15114 &%owner-something%&. Another common use is to support local parts of the form
15115 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
15116 to tell a user their forwarding is broken &-- by placing a router like this one
15117 immediately before the router that handles &_.forward_& files:
15121 local_part_prefix = real-
15123 transport = local_delivery
15125 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
15126 both conditions must be met if not optional. Care must be taken if wildcards
15127 are used in both a prefix and a suffix on the same router. Different
15128 separator characters must be used to avoid ambiguity.
15131 .option local_part_prefix_optional routers boolean false
15132 See &%local_part_prefix%& above.
15136 .option local_part_suffix routers&!? "string list" unset
15137 .cindex "router" "suffix for local part"
15138 .cindex "suffix for local part" "used in router"
15139 This option operates in the same way as &%local_part_prefix%&, except that the
15140 local part must end (rather than start) with the given string, the
15141 &%local_part_suffix_optional%& option determines whether the suffix is
15142 mandatory, and the wildcard * character, if present, must be the last
15143 character of the suffix. This option facility is commonly used to handle local
15144 parts of the form &%something-request%& and multiple user mailboxes of the form
15148 .option local_part_suffix_optional routers boolean false
15149 See &%local_part_suffix%& above.
15153 .option local_parts routers&!? "local part list&!!" unset
15154 .cindex "router" "restricting to specific local parts"
15155 .cindex "local part" "checking in router"
15156 The router is run only if the local part of the address matches the list.
15157 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15159 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
15160 string is expanded, it is possible to make it depend on the domain, for
15163 local_parts = dbm;/usr/local/specials/$domain
15165 .cindex "&$local_part_data$&"
15166 If the match is achieved by a lookup, the data that the lookup returned
15167 for the local part is placed in the variable &$local_part_data$& for use in
15168 expansions of the router's private options. You might use this option, for
15169 example, if you have a large number of local virtual domains, and you want to
15170 send all postmaster mail to the same place without having to set up an alias in
15171 each virtual domain:
15175 local_parts = postmaster
15176 data = postmaster@real.domain.example
15180 .option log_as_local routers boolean "see below"
15181 .cindex "log" "delivery line"
15182 .cindex "delivery" "log line format"
15183 Exim has two logging styles for delivery, the idea being to make local
15184 deliveries stand out more visibly from remote ones. In the &"local"& style, the
15185 recipient address is given just as the local part, without a domain. The use of
15186 this style is controlled by this option. It defaults to true for the &(accept)&
15187 router, and false for all the others. This option applies only when a
15188 router assigns an address to a transport. It has no effect on routers that
15189 redirect addresses.
15193 .option more routers boolean&!! true
15194 The result of string expansion for this option must be a valid boolean value,
15195 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
15196 result causes an error, and delivery is deferred. If the expansion is forced to
15197 fail, the default value for the option (true) is used. Other failures cause
15198 delivery to be deferred.
15200 If this option is set false, and the router declines to handle the address, no
15201 further routers are tried, routing fails, and the address is bounced.
15202 .cindex "&%self%& option"
15203 However, if the router explicitly passes an address to the following router by
15204 means of the setting
15208 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
15209 does not affect the behaviour if one of the precondition tests fails. In that
15210 case, the address is always passed to the next router.
15212 Note that &%address_data%& is not considered to be a precondition. If its
15213 expansion is forced to fail, the router declines, and the value of &%more%&
15214 controls what happens next.
15217 .option pass_on_timeout routers boolean false
15218 .cindex "timeout" "of router"
15219 .cindex "router" "timeout"
15220 If a router times out during a host lookup, it normally causes deferral of the
15221 address. If &%pass_on_timeout%& is set, the address is passed on to the next
15222 router, overriding &%no_more%&. This may be helpful for systems that are
15223 intermittently connected to the Internet, or those that want to pass to a smart
15224 host any messages that cannot immediately be delivered.
15226 There are occasional other temporary errors that can occur while doing DNS
15227 lookups. They are treated in the same way as a timeout, and this option
15228 applies to all of them.
15232 .option pass_router routers string unset
15233 .cindex "router" "go to after &""pass""&"
15234 When a router returns &"pass"&, the address is normally handed on to the next
15235 router in sequence. This can be changed by setting &%pass_router%& to the name
15236 of another router. However (unlike &%redirect_router%&) the named router must
15237 be below the current router, to avoid loops. Note that this option applies only
15238 to the special case of &"pass"&. It does not apply when a router returns
15243 .option redirect_router routers string unset
15244 .cindex "router" "start at after redirection"
15245 Sometimes an administrator knows that it is pointless to reprocess addresses
15246 generated from alias or forward files with the same router again. For
15247 example, if an alias file translates real names into login ids there is no
15248 point searching the alias file a second time, especially if it is a large file.
15250 The &%redirect_router%& option can be set to the name of any router instance.
15251 It causes the routing of any generated addresses to start at the named router
15252 instead of at the first router. This option has no effect if the router in
15253 which it is set does not generate new addresses.
15257 .option require_files routers&!? "string list&!!" unset
15258 .cindex "file" "requiring for router"
15259 .cindex "router" "requiring file existence"
15260 This option provides a general mechanism for predicating the running of a
15261 router on the existence or non-existence of certain files or directories.
15262 Before running a router, as one of its precondition tests, Exim works its way
15263 through the &%require_files%& list, expanding each item separately.
15265 Because the list is split before expansion, any colons in expansion items must
15266 be doubled, or the facility for using a different list separator must be used.
15267 If any expansion is forced to fail, the item is ignored. Other expansion
15268 failures cause routing of the address to be deferred.
15270 If any expanded string is empty, it is ignored. Otherwise, except as described
15271 below, each string must be a fully qualified file path, optionally preceded by
15272 &"!"&. The paths are passed to the &[stat()]& function to test for the
15273 existence of the files or directories. The router is skipped if any paths not
15274 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
15277 If &[stat()]& cannot determine whether a file exists or not, delivery of
15278 the message is deferred. This can happen when NFS-mounted filesystems are
15281 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
15282 options, so you cannot use it to check for the existence of a file in which to
15283 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
15284 full list of the order in which preconditions are evaluated.) However, as
15285 these options are all expanded, you can use the &%exists%& expansion condition
15286 to make such tests. The &%require_files%& option is intended for checking files
15287 that the router may be going to use internally, or which are needed by a
15288 transport (for example &_.procmailrc_&).
15290 During delivery, the &[stat()]& function is run as root, but there is a
15291 facility for some checking of the accessibility of a file by another user.
15292 This is not a proper permissions check, but just a &"rough"& check that
15293 operates as follows:
15295 If an item in a &%require_files%& list does not contain any forward slash
15296 characters, it is taken to be the user (and optional group, separated by a
15297 comma) to be checked for subsequent files in the list. If no group is specified
15298 but the user is specified symbolically, the gid associated with the uid is
15301 require_files = mail:/some/file
15302 require_files = $local_part:$home/.procmailrc
15304 If a user or group name in a &%require_files%& list does not exist, the
15305 &%require_files%& condition fails.
15307 Exim performs the check by scanning along the components of the file path, and
15308 checking the access for the given uid and gid. It checks for &"x"& access on
15309 directories, and &"r"& access on the final file. Note that this means that file
15310 access control lists, if the operating system has them, are ignored.
15312 &*Warning 1*&: When the router is being run to verify addresses for an
15313 incoming SMTP message, Exim is not running as root, but under its own uid. This
15314 may affect the result of a &%require_files%& check. In particular, &[stat()]&
15315 may yield the error EACCES (&"Permission denied"&). This means that the Exim
15316 user is not permitted to read one of the directories on the file's path.
15318 &*Warning 2*&: Even when Exim is running as root while delivering a message,
15319 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
15320 without root access. In this case, if a check for access by a particular user
15321 is requested, Exim creates a subprocess that runs as that user, and tries the
15322 check again in that process.
15324 The default action for handling an unresolved EACCES is to consider it to
15325 be caused by a configuration error, and routing is deferred because the
15326 existence or non-existence of the file cannot be determined. However, in some
15327 circumstances it may be desirable to treat this condition as if the file did
15328 not exist. If the file name (or the exclamation mark that precedes the file
15329 name for non-existence) is preceded by a plus sign, the EACCES error is treated
15330 as if the file did not exist. For example:
15332 require_files = +/some/file
15334 If the router is not an essential part of verification (for example, it
15335 handles users' &_.forward_& files), another solution is to set the &%verify%&
15336 option false so that the router is skipped when verifying.
15340 .option retry_use_local_part routers boolean "see below"
15341 .cindex "hints database" "retry keys"
15342 .cindex "local part" "in retry keys"
15343 When a delivery suffers a temporary routing failure, a retry record is created
15344 in Exim's hints database. For addresses whose routing depends only on the
15345 domain, the key for the retry record should not involve the local part, but for
15346 other addresses, both the domain and the local part should be included.
15347 Usually, remote routing is of the former kind, and local routing is of the
15350 This option controls whether the local part is used to form the key for retry
15351 hints for addresses that suffer temporary errors while being handled by this
15352 router. The default value is true for any router that has &%check_local_user%&
15353 set, and false otherwise. Note that this option does not apply to hints keys
15354 for transport delays; they are controlled by a generic transport option of the
15357 The setting of &%retry_use_local_part%& applies only to the router on which it
15358 appears. If the router generates child addresses, they are routed
15359 independently; this setting does not become attached to them.
15363 .option router_home_directory routers string&!! unset
15364 .cindex "router" "home directory for"
15365 .cindex "home directory" "for router"
15367 This option sets a home directory for use while the router is running. (Compare
15368 &%transport_home_directory%&, which sets a home directory for later
15369 transporting.) In particular, if used on a &(redirect)& router, this option
15370 sets a value for &$home$& while a filter is running. The value is expanded;
15371 forced expansion failure causes the option to be ignored &-- other failures
15372 cause the router to defer.
15374 Expansion of &%router_home_directory%& happens immediately after the
15375 &%check_local_user%& test (if configured), before any further expansions take
15377 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15379 While the router is running, &%router_home_directory%& overrides the value of
15380 &$home$& that came from &%check_local_user%&.
15383 When a router accepts an address and assigns it to a local transport (including
15384 the cases when a &(redirect)& router generates a pipe, file, or autoreply
15385 delivery), the home directory setting for the transport is taken from the first
15386 of these values that is set:
15390 The &%home_directory%& option on the transport;
15392 The &%transport_home_directory%& option on the router;
15394 The password data if &%check_local_user%& is set on the router;
15396 The &%router_home_directory%& option on the router.
15399 In other words, &%router_home_directory%& overrides the password data for the
15400 router, but not for the transport.
15404 .option self routers string freeze
15405 .cindex "MX record" "pointing to local host"
15406 .cindex "local host" "MX pointing to"
15407 This option applies to those routers that use a recipient address to find a
15408 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
15409 and &(manualroute)& routers.
15410 Certain configurations of the &(queryprogram)& router can also specify a list
15412 Usually such routers are configured to send the message to a remote host via an
15413 &(smtp)& transport. The &%self%& option specifies what happens when the first
15414 host on the list turns out to be the local host.
15415 The way in which Exim checks for the local host is described in section
15416 &<<SECTreclocipadd>>&.
15418 Normally this situation indicates either an error in Exim's configuration (for
15419 example, the router should be configured not to process this domain), or an
15420 error in the DNS (for example, the MX should not point to this host). For this
15421 reason, the default action is to log the incident, defer the address, and
15422 freeze the message. The following alternatives are provided for use in special
15427 Delivery of the message is tried again later, but the message is not frozen.
15429 .vitem "&%reroute%&: <&'domain'&>"
15430 The domain is changed to the given domain, and the address is passed back to
15431 be reprocessed by the routers. No rewriting of headers takes place. This
15432 behaviour is essentially a redirection.
15434 .vitem "&%reroute: rewrite:%& <&'domain'&>"
15435 The domain is changed to the given domain, and the address is passed back to be
15436 reprocessed by the routers. Any headers that contain the original domain are
15440 .cindex "&%more%& option"
15441 .cindex "&$self_hostname$&"
15442 The router passes the address to the next router, or to the router named in the
15443 &%pass_router%& option if it is set. This overrides &%no_more%&. During
15444 subsequent routing and delivery, the variable &$self_hostname$& contains the
15445 name of the local host that the router encountered. This can be used to
15446 distinguish between different cases for hosts with multiple names. The
15452 ensures that only those addresses that routed to the local host are passed on.
15453 Without &%no_more%&, addresses that were declined for other reasons would also
15454 be passed to the next router.
15457 Delivery fails and an error report is generated.
15460 .cindex "local host" "sending to"
15461 The anomaly is ignored and the address is queued for the transport. This
15462 setting should be used with extreme caution. For an &(smtp)& transport, it
15463 makes sense only in cases where the program that is listening on the SMTP port
15464 is not this version of Exim. That is, it must be some other MTA, or Exim with a
15465 different configuration file that handles the domain in another way.
15470 .option senders routers&!? "address list&!!" unset
15471 .cindex "router" "checking senders"
15472 If this option is set, the router is skipped unless the message's sender
15473 address matches something on the list.
15474 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15477 There are issues concerning verification when the running of routers is
15478 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
15479 setting, it sets the sender to the null string. When using the &%-bt%& option
15480 to check a configuration file, it is necessary also to use the &%-f%& option to
15481 set an appropriate sender. For incoming mail, the sender is unset when
15482 verifying the sender, but is available when verifying any recipients. If the
15483 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
15487 .option translate_ip_address routers string&!! unset
15488 .cindex "IP address" "translating"
15489 .cindex "packet radio"
15490 .cindex "router" "IP address translation"
15491 There exist some rare networking situations (for example, packet radio) where
15492 it is helpful to be able to translate IP addresses generated by normal routing
15493 mechanisms into other IP addresses, thus performing a kind of manual IP
15494 routing. This should be done only if the normal IP routing of the TCP/IP stack
15495 is inadequate or broken. Because this is an extremely uncommon requirement, the
15496 code to support this option is not included in the Exim binary unless
15497 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
15499 .cindex "&$host_address$&"
15500 The &%translate_ip_address%& string is expanded for every IP address generated
15501 by the router, with the generated address set in &$host_address$&. If the
15502 expansion is forced to fail, no action is taken.
15503 For any other expansion error, delivery of the message is deferred.
15504 If the result of the expansion is an IP address, that replaces the original
15505 address; otherwise the result is assumed to be a host name &-- this is looked
15506 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
15507 produce one or more replacement IP addresses. For example, to subvert all IP
15508 addresses in some specific networks, this could be added to a router:
15510 translate_ip_address = \
15511 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
15514 The file would contain lines like
15516 10.2.3.128/26 some.host
15517 10.8.4.34/26 10.44.8.15
15519 You should not make use of this facility unless you really understand what you
15524 .option transport routers string&!! unset
15525 This option specifies the transport to be used when a router accepts an address
15526 and sets it up for delivery. A transport is never needed if a router is used
15527 only for verification. The value of the option is expanded at routing time,
15528 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
15529 and result must be the name of one of the configured transports. If it is not,
15530 delivery is deferred.
15532 The &%transport%& option is not used by the &(redirect)& router, but it does
15533 have some private options that set up transports for pipe and file deliveries
15534 (see chapter &<<CHAPredirect>>&).
15538 .option transport_current_directory routers string&!! unset
15539 .cindex "current directory for local transport"
15540 This option associates a current directory with any address that is routed
15541 to a local transport. This can happen either because a transport is
15542 explicitly configured for the router, or because it generates a delivery to a
15543 file or a pipe. During the delivery process (that is, at transport time), this
15544 option string is expanded and is set as the current directory, unless
15545 overridden by a setting on the transport.
15546 If the expansion fails for any reason, including forced failure, an error is
15547 logged, and delivery is deferred.
15548 See chapter &<<CHAPenvironment>>& for details of the local delivery
15554 .option transport_home_directory routers string&!! "see below"
15555 .cindex "home directory" "for local transport"
15556 This option associates a home directory with any address that is routed to a
15557 local transport. This can happen either because a transport is explicitly
15558 configured for the router, or because it generates a delivery to a file or a
15559 pipe. During the delivery process (that is, at transport time), the option
15560 string is expanded and is set as the home directory, unless overridden by a
15561 setting of &%home_directory%& on the transport.
15562 If the expansion fails for any reason, including forced failure, an error is
15563 logged, and delivery is deferred.
15565 If the transport does not specify a home directory, and
15566 &%transport_home_directory%& is not set for the router, the home directory for
15567 the tranport is taken from the password data if &%check_local_user%& is set for
15568 the router. Otherwise it is taken from &%router_home_directory%& if that option
15569 is set; if not, no home directory is set for the transport.
15571 See chapter &<<CHAPenvironment>>& for further details of the local delivery
15577 .option unseen routers boolean&!! false
15578 .cindex "router" "carrying on after success"
15579 The result of string expansion for this option must be a valid boolean value,
15580 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
15581 result causes an error, and delivery is deferred. If the expansion is forced to
15582 fail, the default value for the option (false) is used. Other failures cause
15583 delivery to be deferred.
15585 When this option is set true, routing does not cease if the router accepts the
15586 address. Instead, a copy of the incoming address is passed to the next router,
15587 overriding a false setting of &%more%&. There is little point in setting
15588 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
15589 the value of &%unseen%& contains expansion items (and therefore, presumably, is
15590 sometimes true and sometimes false).
15592 .cindex "copy of message (&%unseen%& option)"
15593 The &%unseen%& option can be used to cause copies of messages to be delivered
15594 to some other destination, while also carrying out a normal delivery. In
15595 effect, the current address is made into a &"parent"& that has two children &--
15596 one that is delivered as specified by this router, and a clone that goes on to
15597 be routed further. For this reason, &%unseen%& may not be combined with the
15598 &%one_time%& option in a &(redirect)& router.
15600 &*Warning*&: Header lines added to the address (or specified for removal) by
15601 this router or by previous routers affect the &"unseen"& copy of the message
15602 only. The clone that continues to be processed by further routers starts with
15603 no added headers and none specified for removal. However, any data that was set
15604 by the &%address_data%& option in the current or previous routers is passed on.
15605 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
15606 qualifier in filter files.
15610 .option user routers string&!! "see below"
15611 .cindex "uid (user id)" "local delivery"
15612 .cindex "local transports" "uid and gid"
15613 .cindex "transport" "local"
15614 .cindex "router" "user for filter processing"
15615 .cindex "filter" "user for processing"
15616 When a router queues an address for a transport, and the transport does not
15617 specify a user, the user given here is used when running the delivery process.
15618 The user may be specified numerically or by name. If expansion fails, the
15619 error is logged and delivery is deferred.
15620 This user is also used by the &(redirect)& router when running a filter file.
15621 The default is unset, except when &%check_local_user%& is set. In this case,
15622 the default is taken from the password information. If the user is specified as
15623 a name, and &%group%& is not set, the group associated with the user is used.
15624 See also &%initgroups%& and &%group%& and the discussion in chapter
15625 &<<CHAPenvironment>>&.
15629 .option verify routers&!? boolean true
15630 Setting this option has the effect of setting &%verify_sender%& and
15631 &%verify_recipient%& to the same value.
15634 .option verify_only routers&!? boolean false
15635 .cindex "EXPN" "with &%verify_only%&"
15636 .cindex "&%-bv%& option"
15637 .cindex "router" "used only when verifying"
15638 If this option is set, the router is used only when verifying an address or
15639 testing with the &%-bv%& option, not when actually doing a delivery, testing
15640 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
15641 restricted to verifying only senders or recipients by means of
15642 &%verify_sender%& and &%verify_recipient%&.
15644 &*Warning*&: When the router is being run to verify addresses for an incoming
15645 SMTP message, Exim is not running as root, but under its own uid. If the router
15646 accesses any files, you need to make sure that they are accessible to the Exim
15650 .option verify_recipient routers&!? boolean true
15651 If this option is false, the router is skipped when verifying recipient
15653 or testing recipient verification using &%-bv%&.
15654 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15658 .option verify_sender routers&!? boolean true
15659 If this option is false, the router is skipped when verifying sender addresses
15660 or testing sender verification using &%-bvs%&.
15661 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15663 .ecindex IIDgenoprou1
15664 .ecindex IIDgenoprou2
15671 . ////////////////////////////////////////////////////////////////////////////
15672 . ////////////////////////////////////////////////////////////////////////////
15674 .chapter "The accept router"
15675 .cindex "&(accept)& router"
15676 .cindex "routers" "&(accept)&"
15677 The &(accept)& router has no private options of its own. Unless it is being
15678 used purely for verification (see &%verify_only%&) a transport is required to
15679 be defined by the generic &%transport%& option. If the preconditions that are
15680 specified by generic options are met, the router accepts the address and queues
15681 it for the given transport. The most common use of this router is for setting
15682 up deliveries to local mailboxes. For example:
15686 domains = mydomain.example
15688 transport = local_delivery
15690 The &%domains%& condition in this example checks the domain of the address, and
15691 &%check_local_user%& checks that the local part is the login of a local user.
15692 When both preconditions are met, the &(accept)& router runs, and queues the
15693 address for the &(local_delivery)& transport.
15700 . ////////////////////////////////////////////////////////////////////////////
15701 . ////////////////////////////////////////////////////////////////////////////
15703 .chapter "The dnslookup router" "CHAPdnslookup"
15704 .scindex IIDdnsrou1 "&(dnslookup)& router"
15705 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
15706 The &(dnslookup)& router looks up the hosts that handle mail for the
15707 recipient's domain in the DNS. A transport must always be set for this router,
15708 unless &%verify_only%& is set.
15710 If SRV support is configured (see &%check_srv%& below), Exim first searches for
15711 SRV records. If none are found, or if SRV support is not configured,
15712 MX records are looked up. If no MX records exist, address records are sought.
15713 However, &%mx_domains%& can be set to disable the direct use of address
15716 MX records of equal priority are sorted by Exim into a random order. Exim then
15717 looks for address records for the host names obtained from MX or SRV records.
15718 When a host has more than one IP address, they are sorted into a random order,
15719 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
15720 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
15721 generic option, the router declines.
15723 Unless they have the highest priority (lowest MX value), MX records that point
15724 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
15725 are discarded, together with any other MX records of equal or lower priority.
15727 .cindex "MX record" "pointing to local host"
15728 .cindex "local host" "MX pointing to"
15729 .cindex "&%self%& option" "in &(dnslookup)& router"
15730 If the host pointed to by the highest priority MX record, or looked up as an
15731 address record, is the local host, or matches &%hosts_treat_as_local%&, what
15732 happens is controlled by the generic &%self%& option.
15735 .section "Problems with DNS lookups" "SECTprowitdnsloo"
15736 There have been problems with DNS servers when SRV records are looked up.
15737 Some mis-behaving servers return a DNS error or timeout when a non-existent
15738 SRV record is sought. Similar problems have in the past been reported for
15739 MX records. The global &%dns_again_means_nonexist%& option can help with this
15740 problem, but it is heavy-handed because it is a global option.
15742 For this reason, there are two options, &%srv_fail_domains%& and
15743 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
15744 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
15745 an attempt to look up an SRV or MX record causes one of these results, and the
15746 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
15747 such record"&. In the case of an SRV lookup, this means that the router
15748 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
15749 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
15750 case routing fails.
15755 .section "Private options for dnslookup"
15756 .cindex "options" "&(dnslookup)& router"
15757 The private options for the &(dnslookup)& router are as follows:
15759 .option check_secondary_mx dnslookup boolean false
15760 .cindex "MX record" "checking for secondary"
15761 If this option is set, the router declines unless the local host is found in
15762 (and removed from) the list of hosts obtained by MX lookup. This can be used to
15763 process domains for which the local host is a secondary mail exchanger
15764 differently to other domains. The way in which Exim decides whether a host is
15765 the local host is described in section &<<SECTreclocipadd>>&.
15768 .option check_srv dnslookup string&!! unset
15769 .cindex "SRV record" "enabling use of"
15770 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
15771 addition to MX and address records. The support is disabled by default. To
15772 enable SRV support, set the &%check_srv%& option to the name of the service
15773 required. For example,
15777 looks for SRV records that refer to the normal smtp service. The option is
15778 expanded, so the service name can vary from message to message or address
15779 to address. This might be helpful if SRV records are being used for a
15780 submission service. If the expansion is forced to fail, the &%check_srv%&
15781 option is ignored, and the router proceeds to look for MX records in the
15784 When the expansion succeeds, the router searches first for SRV records for
15785 the given service (it assumes TCP protocol). A single SRV record with a
15786 host name that consists of just a single dot indicates &"no such service for
15787 this domain"&; if this is encountered, the router declines. If other kinds of
15788 SRV record are found, they are used to construct a host list for delivery
15789 according to the rules of RFC 2782. MX records are not sought in this case.
15791 When no SRV records are found, MX records (and address records) are sought in
15792 the traditional way. In other words, SRV records take precedence over MX
15793 records, just as MX records take precedence over address records. Note that
15794 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
15795 defined it. It is apparently believed that MX records are sufficient for email
15796 and that SRV records should not be used for this purpose. However, SRV records
15797 have an additional &"weight"& feature which some people might find useful when
15798 trying to split an SMTP load between hosts of different power.
15800 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
15801 when there is a DNS lookup error.
15805 .option mx_domains dnslookup "domain list&!!" unset
15806 .cindex "MX record" "required to exist"
15807 .cindex "SRV record" "required to exist"
15808 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
15809 record in order to be recognised. (The name of this option could be improved.)
15810 For example, if all the mail hosts in &'fict.example'& are known to have MX
15811 records, except for those in &'discworld.fict.example'&, you could use this
15814 mx_domains = ! *.discworld.fict.example : *.fict.example
15816 This specifies that messages addressed to a domain that matches the list but
15817 has no MX record should be bounced immediately instead of being routed using
15818 the address record.
15821 .option mx_fail_domains dnslookup "domain list&!!" unset
15822 If the DNS lookup for MX records for one of the domains in this list causes a
15823 DNS lookup error, Exim behaves as if no MX records were found. See section
15824 &<<SECTprowitdnsloo>>& for more discussion.
15829 .option qualify_single dnslookup boolean true
15830 .cindex "DNS" "resolver options"
15831 .cindex "DNS" "qualifying single-component names"
15832 When this option is true, the resolver option RES_DEFNAMES is set for DNS
15833 lookups. Typically, but not standardly, this causes the resolver to qualify
15834 single-component names with the default domain. For example, on a machine
15835 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
15836 &'thesaurus.ref.example'& inside the resolver. For details of what your
15837 resolver actually does, consult your man pages for &'resolver'& and
15842 .option rewrite_headers dnslookup boolean true
15843 .cindex "rewriting" "header lines"
15844 .cindex "header lines" "rewriting"
15845 If the domain name in the address that is being processed is not fully
15846 qualified, it may be expanded to its full form by a DNS lookup. For example, if
15847 an address is specified as &'dormouse@teaparty'&, the domain might be
15848 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
15849 occur as a result of setting the &%widen_domains%& option. If
15850 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
15851 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
15852 header lines of the message are rewritten with the full domain name.
15854 This option should be turned off only when it is known that no message is
15855 ever going to be sent outside an environment where the abbreviation makes
15858 When an MX record is looked up in the DNS and matches a wildcard record, name
15859 servers normally return a record containing the name that has been looked up,
15860 making it impossible to detect whether a wildcard was present or not. However,
15861 some name servers have recently been seen to return the wildcard entry. If the
15862 name returned by a DNS lookup begins with an asterisk, it is not used for
15866 .option same_domain_copy_routing dnslookup boolean false
15867 .cindex "address" "copying routing"
15868 Addresses with the same domain are normally routed by the &(dnslookup)& router
15869 to the same list of hosts. However, this cannot be presumed, because the router
15870 options and preconditions may refer to the local part of the address. By
15871 default, therefore, Exim routes each address in a message independently. DNS
15872 servers run caches, so repeated DNS lookups are not normally expensive, and in
15873 any case, personal messages rarely have more than a few recipients.
15875 If you are running mailing lists with large numbers of subscribers at the same
15876 domain, and you are using a &(dnslookup)& router which is independent of the
15877 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
15878 lookups for identical domains in one message. In this case, when &(dnslookup)&
15879 routes an address to a remote transport, any other unrouted addresses in the
15880 message that have the same domain are automatically given the same routing
15881 without processing them independently,
15882 provided the following conditions are met:
15885 No router that processed the address specified &%headers_add%& or
15886 &%headers_remove%&.
15888 The router did not change the address in any way, for example, by &"widening"&
15895 .option search_parents dnslookup boolean false
15896 .cindex "DNS" "resolver options"
15897 When this option is true, the resolver option RES_DNSRCH is set for DNS
15898 lookups. This is different from the &%qualify_single%& option in that it
15899 applies to domains containing dots. Typically, but not standardly, it causes
15900 the resolver to search for the name in the current domain and in parent
15901 domains. For example, on a machine in the &'fict.example'& domain, if looking
15902 up &'teaparty.wonderland'& failed, the resolver would try
15903 &'teaparty.wonderland.fict.example'&. For details of what your resolver
15904 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
15906 Setting this option true can cause problems in domains that have a wildcard MX
15907 record, because any domain that does not have its own MX record matches the
15912 .option srv_fail_domains dnslookup "domain list&!!" unset
15913 If the DNS lookup for SRV records for one of the domains in this list causes a
15914 DNS lookup error, Exim behaves as if no SRV records were found. See section
15915 &<<SECTprowitdnsloo>>& for more discussion.
15920 .option widen_domains dnslookup "string list" unset
15921 .cindex "domain" "partial; widening"
15922 If a DNS lookup fails and this option is set, each of its strings in turn is
15923 added onto the end of the domain, and the lookup is tried again. For example,
15926 widen_domains = fict.example:ref.example
15928 is set and a lookup of &'klingon.dictionary'& fails,
15929 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
15930 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
15931 and &%search_parents%& options can cause some widening to be undertaken inside
15932 the DNS resolver. &%widen_domains%& is not applied to sender addresses
15933 when verifying, unless &%rewrite_headers%& is false (not the default).
15936 .section "Effect of qualify_single and search_parents"
15937 When a domain from an envelope recipient is changed by the resolver as a result
15938 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
15939 corresponding address in the message's header lines unless &%rewrite_headers%&
15940 is set false. Exim then re-routes the address, using the full domain.
15942 These two options affect only the DNS lookup that takes place inside the router
15943 for the domain of the address that is being routed. They do not affect lookups
15944 such as that implied by
15948 that may happen while processing a router precondition before the router is
15949 entered. No widening ever takes place for these lookups.
15950 .ecindex IIDdnsrou1
15951 .ecindex IIDdnsrou2
15961 . ////////////////////////////////////////////////////////////////////////////
15962 . ////////////////////////////////////////////////////////////////////////////
15964 .chapter "The ipliteral router"
15965 .cindex "&(ipliteral)& router"
15966 .cindex "domain literal" "routing"
15967 .cindex "routers" "&(ipliteral)&"
15968 This router has no private options. Unless it is being used purely for
15969 verification (see &%verify_only%&) a transport is required to be defined by the
15970 generic &%transport%& option. The router accepts the address if its domain part
15971 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
15972 router handles the address
15977 by setting up delivery to the host with that IP address. IPv4 domain literals
15978 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
15979 are similar, but the address is preceded by &`ipv6:`&. For example:
15981 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
15983 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
15984 grounds that sooner or later somebody will try it.
15987 .cindex "&%self%& option" "in &(ipliteral)& router"
15988 If the IP address matches something in &%ignore_target_hosts%&, the router
15989 declines. If an IP literal turns out to refer to the local host, the generic
15990 &%self%& option determines what happens.
15992 The RFCs require support for domain literals; however, their use is
15993 controversial in today's Internet. If you want to use this router, you must
15994 also set the main configuration option &%allow_domain_literals%&. Otherwise,
15995 Exim will not recognize the domain literal syntax in addresses.
15999 . ////////////////////////////////////////////////////////////////////////////
16000 . ////////////////////////////////////////////////////////////////////////////
16002 .chapter "The iplookup router"
16003 .cindex "&(iplookup)& router"
16004 .cindex "routers" "&(iplookup)&"
16005 The &(iplookup)& router was written to fulfil a specific requirement in
16006 Cambridge University (which in fact no longer exists). For this reason, it is
16007 not included in the binary of Exim by default. If you want to include it, you
16010 ROUTER_IPLOOKUP=yes
16012 in your &_Local/Makefile_& configuration file.
16014 The &(iplookup)& router routes an address by sending it over a TCP or UDP
16015 connection to one or more specific hosts. The host can then return the same or
16016 a different address &-- in effect rewriting the recipient address in the
16017 message's envelope. The new address is then passed on to subsequent routers. If
16018 this process fails, the address can be passed on to other routers, or delivery
16019 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
16020 must not be specified for it.
16022 .cindex "options" "&(iplookup)& router"
16023 .option hosts iplookup string unset
16024 This option must be supplied. Its value is a colon-separated list of host
16025 names. The hosts are looked up using &[gethostbyname()]&
16026 (or &[getipnodebyname()]& when available)
16027 and are tried in order until one responds to the query. If none respond, what
16028 happens is controlled by &%optional%&.
16031 .option optional iplookup boolean false
16032 If &%optional%& is true, if no response is obtained from any host, the address
16033 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
16034 delivery to the address is deferred.
16037 .option port iplookup integer 0
16038 .cindex "port" "&(iplookup)& router"
16039 This option must be supplied. It specifies the port number for the TCP or UDP
16043 .option protocol iplookup string udp
16044 This option can be set to &"udp"& or &"tcp"& to specify which of the two
16045 protocols is to be used.
16048 .option query iplookup string&!! "&`$local_part@$domain $local_part@$domain`&"
16049 This defines the content of the query that is sent to the remote hosts. The
16050 repetition serves as a way of checking that a response is to the correct query
16051 in the default case (see &%response_pattern%& below).
16054 .option reroute iplookup string&!! unset
16055 If this option is not set, the rerouted address is precisely the byte string
16056 returned by the remote host, up to the first white space, if any. If set, the
16057 string is expanded to form the rerouted address. It can include parts matched
16058 in the response by &%response_pattern%& by means of numeric variables such as
16059 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
16060 whether or not a pattern is in use. In all cases, the rerouted address must end
16061 up in the form &'local_part@domain'&.
16064 .option response_pattern iplookup string unset
16065 This option can be set to a regular expression that is applied to the string
16066 returned from the remote host. If the pattern does not match the response, the
16067 router declines. If &%response_pattern%& is not set, no checking of the
16068 response is done, unless the query was defaulted, in which case there is a
16069 check that the text returned after the first white space is the original
16070 address. This checks that the answer that has been received is in response to
16071 the correct question. For example, if the response is just a new domain, the
16072 following could be used:
16074 response_pattern = ^([^@]+)$
16075 reroute = $local_part@$1
16078 .option timeout iplookup time 5s
16079 This specifies the amount of time to wait for a response from the remote
16080 machine. The same timeout is used for the &[connect()]& function for a TCP
16081 call. It does not apply to UDP.
16086 . ////////////////////////////////////////////////////////////////////////////
16087 . ////////////////////////////////////////////////////////////////////////////
16089 .chapter "The manualroute router"
16090 .scindex IIDmanrou1 "&(manualroute)& router"
16091 .scindex IIDmanrou2 "routers" "&(manualroute)&"
16092 .cindex "domain" "manually routing"
16093 The &(manualroute)& router is so-called because it provides a way of manually
16094 routing an address according to its domain. It is mainly used when you want to
16095 route addresses to remote hosts according to your own rules, bypassing the
16096 normal DNS routing that looks up MX records. However, &(manualroute)& can also
16097 route to local transports, a facility that may be useful if you want to save
16098 messages for dial-in hosts in local files.
16100 The &(manualroute)& router compares a list of domain patterns with the domain
16101 it is trying to route. If there is no match, the router declines. Each pattern
16102 has associated with it a list of hosts and some other optional data, which may
16103 include a transport. The combination of a pattern and its data is called a
16104 &"routing rule"&. For patterns that do not have an associated transport, the
16105 generic &%transport%& option must specify a transport, unless the router is
16106 being used purely for verification (see &%verify_only%&).
16109 In the case of verification, matching the domain pattern is sufficient for the
16110 router to accept the address. When actually routing an address for delivery,
16111 an address that matches a domain pattern is queued for the associated
16112 transport. If the transport is not a local one, a host list must be associated
16113 with the pattern; IP addresses are looked up for the hosts, and these are
16114 passed to the transport along with the mail address. For local transports, a
16115 host list is optional. If it is present, it is passed in &$host$& as a single
16118 The list of routing rules can be provided as an inline string in
16119 &%route_list%&, or the data can be obtained by looking up the domain in a file
16120 or database by setting &%route_data%&. Only one of these settings may appear in
16121 any one instance of &(manualroute)&. The format of routing rules is described
16122 below, following the list of private options.
16125 .section "Private options for manualroute" "SECTprioptman"
16127 .cindex "options" "&(manualroute)& router"
16128 The private options for the &(manualroute)& router are as follows:
16131 .option host_find_failed manualroute string freeze
16132 This option controls what happens when &(manualroute)& tries to find an IP
16133 address for a host, and the host does not exist. The option can be set to one
16142 The default assumes that this state is a serious configuration error. The
16143 difference between &"pass"& and &"decline"& is that the former forces the
16144 address to be passed to the next router (or the router defined by
16146 .cindex "&%more%& option"
16147 overriding &%no_more%&, whereas the latter passes the address to the next
16148 router only if &%more%& is true.
16150 This option applies only to a definite &"does not exist"& state; if a host
16151 lookup gets a temporary error, delivery is deferred unless the generic
16152 &%pass_on_timeout%& option is set.
16155 .option hosts_randomize manualroute boolean false
16156 .cindex "randomized host list"
16157 .cindex "host" "list of; randomized"
16158 If this option is set, the order of the items in a host list in a routing rule
16159 is randomized each time the list is used, unless an option in the routing rule
16160 overrides (see below). Randomizing the order of a host list can be used to do
16161 crude load sharing. However, if more than one mail address is routed by the
16162 same router to the same host list, the host lists are considered to be the same
16163 (even though they may be randomized into different orders) for the purpose of
16164 deciding whether to batch the deliveries into a single SMTP transaction.
16166 When &%hosts_randomize%& is true, a host list may be split
16167 into groups whose order is separately randomized. This makes it possible to
16168 set up MX-like behaviour. The boundaries between groups are indicated by an
16169 item that is just &`+`& in the host list. For example:
16171 route_list = * host1:host2:host3:+:host4:host5
16173 The order of the first three hosts and the order of the last two hosts is
16174 randomized for each use, but the first three always end up before the last two.
16175 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
16176 randomized host list is passed to an &(smtp)& transport that also has
16177 &%hosts_randomize set%&, the list is not re-randomized.
16180 .option route_data manualroute string&!! unset
16181 If this option is set, it must expand to yield the data part of a routing rule.
16182 Typically, the expansion string includes a lookup based on the domain. For
16185 route_data = ${lookup{$domain}dbm{/etc/routes}}
16187 If the expansion is forced to fail, or the result is an empty string, the
16188 router declines. Other kinds of expansion failure cause delivery to be
16192 .option route_list manualroute " "string list" " semicolon-separated""
16193 This string is a list of routing rules, in the form defined below. Note that,
16194 unlike most string lists, the items are separated by semicolons. This is so
16195 that they may contain colon-separated host lists.
16198 .option same_domain_copy_routing manualroute boolean false
16199 .cindex "address" "copying routing"
16200 Addresses with the same domain are normally routed by the &(manualroute)&
16201 router to the same list of hosts. However, this cannot be presumed, because the
16202 router options and preconditions may refer to the local part of the address. By
16203 default, therefore, Exim routes each address in a message independently. DNS
16204 servers run caches, so repeated DNS lookups are not normally expensive, and in
16205 any case, personal messages rarely have more than a few recipients.
16207 If you are running mailing lists with large numbers of subscribers at the same
16208 domain, and you are using a &(manualroute)& router which is independent of the
16209 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
16210 lookups for identical domains in one message. In this case, when
16211 &(manualroute)& routes an address to a remote transport, any other unrouted
16212 addresses in the message that have the same domain are automatically given the
16213 same routing without processing them independently. However, this is only done
16214 if &%headers_add%& and &%headers_remove%& are unset.
16219 .section "Routing rules in route_list"
16220 The value of &%route_list%& is a string consisting of a sequence of routing
16221 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
16222 entered as two semicolons. Alternatively, the list separator can be changed as
16223 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
16224 Empty rules are ignored. The format of each rule is
16226 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
16228 The following example contains two rules, each with a simple domain pattern and
16232 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
16233 thes.ref.example mail-3.ref.example:mail-4.ref.example
16235 The three parts of a rule are separated by white space. The pattern and the
16236 list of hosts can be enclosed in quotes if necessary, and if they are, the
16237 usual quoting rules apply. Each rule in a &%route_list%& must start with a
16238 single domain pattern, which is the only mandatory item in the rule. The
16239 pattern is in the same format as one item in a domain list (see section
16240 &<<SECTdomainlist>>&),
16241 except that it may not be the name of an interpolated file.
16242 That is, it may be wildcarded, or a regular expression, or a file or database
16243 lookup (with semicolons doubled, because of the use of semicolon as a separator
16244 in a &%route_list%&).
16246 The rules in &%route_list%& are searched in order until one of the patterns
16247 matches the domain that is being routed. The list of hosts and then options are
16248 then used as described below. If there is no match, the router declines. When
16249 &%route_list%& is set, &%route_data%& must not be set.
16253 .section "Routing rules in route_data"
16254 The use of &%route_list%& is convenient when there are only a small number of
16255 routing rules. For larger numbers, it is easier to use a file or database to
16256 hold the routing information, and use the &%route_data%& option instead.
16257 The value of &%route_data%& is a list of hosts, followed by (optional) options.
16258 Most commonly, &%route_data%& is set as a string that contains an
16259 expansion lookup. For example, suppose we place two routing rules in a file
16262 dict.ref.example: mail-1.ref.example:mail-2.ref.example
16263 thes.ref.example: mail-3.ref.example:mail-4.ref.example
16265 This data can be accessed by setting
16267 route_data = ${lookup{$domain}lsearch{/the/file/name}}
16269 Failure of the lookup results in an empty string, causing the router to
16270 decline. However, you do not have to use a lookup in &%route_data%&. The only
16271 requirement is that the result of expanding the string is a list of hosts,
16272 possibly followed by options, separated by white space. The list of hosts must
16273 be enclosed in quotes if it contains white space.
16278 .section "Format of the list of hosts"
16279 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
16280 always separately expanded before use. If the expansion fails, the router
16281 declines. The result of the expansion must be a colon-separated list of names
16282 and/or IP addresses, optionally also including ports. The format of each item
16283 in the list is described in the next section. The list separator can be changed
16284 as described in section &<<SECTlistconstruct>>&.
16286 If the list of hosts was obtained from a &%route_list%& item, the following
16287 variables are set during its expansion:
16290 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
16291 If the domain was matched against a regular expression, the numeric variables
16292 &$1$&, &$2$&, etc. may be set. For example:
16294 route_list = ^domain(\d+) host-$1.text.example
16297 &$0$& is always set to the entire domain.
16299 &$1$& is also set when partial matching is done in a file lookup.
16302 .cindex "&$value$&"
16303 If the pattern that matched the domain was a lookup item, the data that was
16304 looked up is available in the expansion variable &$value$&. For example:
16306 route_list = lsearch;;/some/file.routes $value
16310 Note the doubling of the semicolon in the pattern that is necessary because
16311 semicolon is the default route list separator.
16315 .section "Format of one host item" "SECTformatonehostitem"
16316 Each item in the list of hosts is either a host name or an IP address,
16317 optionally with an attached port number. When no port is given, an IP address
16318 is not enclosed in brackets. When a port is specified, it overrides the port
16319 specification on the transport. The port is separated from the name or address
16320 by a colon. This leads to some complications:
16323 Because colon is the default separator for the list of hosts, either
16324 the colon that specifies a port must be doubled, or the list separator must
16325 be changed. The following two examples have the same effect:
16327 route_list = * "host1.tld::1225 : host2.tld::1226"
16328 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
16331 When IPv6 addresses are involved, it gets worse, because they contain
16332 colons of their own. To make this case easier, it is permitted to
16333 enclose an IP address (either v4 or v6) in square brackets if a port
16334 number follows. For example:
16336 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
16340 .section "How the list of hosts is used" "SECThostshowused"
16341 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
16342 the hosts is tried, in the order specified, when carrying out the SMTP
16343 delivery. However, the order can be changed by setting the &%hosts_randomize%&
16344 option, either on the router (see section &<<SECTprioptman>>& above), or on the
16347 Hosts may be listed by name or by IP address. An unadorned name in the list of
16348 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
16349 interpreted as an indirection to a sublist of hosts obtained by looking up MX
16350 records in the DNS. For example:
16352 route_list = * x.y.z:p.q.r/MX:e.f.g
16354 If this feature is used with a port specifier, the port must come last. For
16357 route_list = * dom1.tld/mx::1225
16359 If the &%hosts_randomize%& option is set, the order of the items in the list is
16360 randomized before any lookups are done. Exim then scans the list; for any name
16361 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
16362 be an interface on the local host and the item is not the first in the list,
16363 Exim discards it and any subsequent items. If it is the first item, what
16364 happens is controlled by the
16365 .cindex "&%self%& option" "in &(manualroute)& router"
16366 &%self%& option of the router.
16368 A name on the list that is followed by &`/MX`& is replaced with the list of
16369 hosts obtained by looking up MX records for the name. This is always a DNS
16370 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
16371 below) are not relevant here. The order of these hosts is determined by the
16372 preference values in the MX records, according to the usual rules. Because
16373 randomizing happens before the MX lookup, it does not affect the order that is
16374 defined by MX preferences.
16376 If the local host is present in the sublist obtained from MX records, but is
16377 not the most preferred host in that list, it and any equally or less
16378 preferred hosts are removed before the sublist is inserted into the main list.
16380 If the local host is the most preferred host in the MX list, what happens
16381 depends on where in the original list of hosts the &`/MX`& item appears. If it
16382 is not the first item (that is, there are previous hosts in the main list),
16383 Exim discards this name and any subsequent items in the main list.
16385 If the MX item is first in the list of hosts, and the local host is the
16386 most preferred host, what happens is controlled by the &%self%& option of the
16389 DNS failures when lookup up the MX records are treated in the same way as DNS
16390 failures when looking up IP addresses: &%pass_on_timeout%& and
16391 &%host_find_failed%& are used when relevant.
16393 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
16394 whether obtained from an MX lookup or not.
16398 .section "How the options are used" "SECThowoptused"
16399 The options are a sequence of words; in practice no more than three are ever
16400 present. One of the words can be the name of a transport; this overrides the
16401 &%transport%& option on the router for this particular routing rule only. The
16402 other words (if present) control randomization of the list of hosts on a
16403 per-rule basis, and how the IP addresses of the hosts are to be found when
16404 routing to a remote transport. These options are as follows:
16407 &%randomize%&: randomize the order of the hosts in this list, overriding the
16408 setting of &%hosts_randomize%& for this routing rule only.
16410 &%no_randomize%&: do not randomize the order of the hosts in this list,
16411 overriding the setting of &%hosts_randomize%& for this routing rule only.
16413 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
16414 find IP addresses. This function may ultimately cause a DNS lookup, but it may
16415 also look in &_/etc/hosts_& or other sources of information.
16417 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
16418 no address records are found. If there is a temporary DNS error (such as a
16419 timeout), delivery is deferred.
16424 route_list = domain1 host1:host2:host3 randomize bydns;\
16425 domain2 host4:host5
16427 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
16428 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
16429 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
16430 or &[gethostbyname()]&, and the result of the lookup is the result of that
16433 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
16434 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
16435 instead of TRY_AGAIN. That is why the default action is to try a DNS
16436 lookup first. Only if that gives a definite &"no such host"& is the local
16441 If no IP address for a host can be found, what happens is controlled by the
16442 &%host_find_failed%& option.
16445 When an address is routed to a local transport, IP addresses are not looked up.
16446 The host list is passed to the transport in the &$host$& variable.
16450 .section "Manualroute examples"
16451 In some of the examples that follow, the presence of the &%remote_smtp%&
16452 transport, as defined in the default configuration file, is assumed:
16455 .cindex "smart host" "example router"
16456 The &(manualroute)& router can be used to forward all external mail to a
16457 &'smart host'&. If you have set up, in the main part of the configuration, a
16458 named domain list that contains your local domains, for example:
16460 domainlist local_domains = my.domain.example
16462 You can arrange for all other domains to be routed to a smart host by making
16463 your first router something like this:
16466 driver = manualroute
16467 domains = !+local_domains
16468 transport = remote_smtp
16469 route_list = * smarthost.ref.example
16471 This causes all non-local addresses to be sent to the single host
16472 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
16473 they are tried in order
16474 (but you can use &%hosts_randomize%& to vary the order each time).
16475 Another way of configuring the same thing is this:
16478 driver = manualroute
16479 transport = remote_smtp
16480 route_list = !+local_domains smarthost.ref.example
16482 There is no difference in behaviour between these two routers as they stand.
16483 However, they behave differently if &%no_more%& is added to them. In the first
16484 example, the router is skipped if the domain does not match the &%domains%&
16485 precondition; the following router is always tried. If the router runs, it
16486 always matches the domain and so can never decline. Therefore, &%no_more%&
16487 would have no effect. In the second case, the router is never skipped; it
16488 always runs. However, if it doesn't match the domain, it declines. In this case
16489 &%no_more%& would prevent subsequent routers from running.
16492 .cindex "mail hub example"
16493 A &'mail hub'& is a host which receives mail for a number of domains via MX
16494 records in the DNS and delivers it via its own private routing mechanism. Often
16495 the final destinations are behind a firewall, with the mail hub being the one
16496 machine that can connect to machines both inside and outside the firewall. The
16497 &(manualroute)& router is usually used on a mail hub to route incoming messages
16498 to the correct hosts. For a small number of domains, the routing can be inline,
16499 using the &%route_list%& option, but for a larger number a file or database
16500 lookup is easier to manage.
16502 If the domain names are in fact the names of the machines to which the mail is
16503 to be sent by the mail hub, the configuration can be quite simple. For
16507 driver = manualroute
16508 transport = remote_smtp
16509 route_list = *.rhodes.tvs.example $domain
16511 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
16512 whose names are the same as the mail domains. A similar approach can be taken
16513 if the host name can be obtained from the domain name by a string manipulation
16514 that the expansion facilities can handle. Otherwise, a lookup based on the
16515 domain can be used to find the host:
16518 driver = manualroute
16519 transport = remote_smtp
16520 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
16522 The result of the lookup must be the name or IP address of the host (or
16523 hosts) to which the address is to be routed. If the lookup fails, the route
16524 data is empty, causing the router to decline. The address then passes to the
16528 .cindex "batched SMTP output example"
16529 .cindex "SMTP" "batched outgoing; example"
16530 You can use &(manualroute)& to deliver messages to pipes or files in batched
16531 SMTP format for onward transportation by some other means. This is one way of
16532 storing mail for a dial-up host when it is not connected. The route list entry
16533 can be as simple as a single domain name in a configuration like this:
16536 driver = manualroute
16537 transport = batchsmtp_appendfile
16538 route_list = saved.domain.example
16540 though often a pattern is used to pick up more than one domain. If there are
16541 several domains or groups of domains with different transport requirements,
16542 different transports can be listed in the routing information:
16545 driver = manualroute
16547 *.saved.domain1.example $domain batch_appendfile; \
16548 *.saved.domain2.example \
16549 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
16552 .cindex "&$domain$&"
16554 The first of these just passes the domain in the &$host$& variable, which
16555 doesn't achieve much (since it is also in &$domain$&), but the second does a
16556 file lookup to find a value to pass, causing the router to decline to handle
16557 the address if the lookup fails.
16560 .cindex "UUCP" "example of router for"
16561 Routing mail directly to UUCP software is a specific case of the use of
16562 &(manualroute)& in a gateway to another mail environment. This is an example of
16563 one way it can be done:
16569 command = /usr/local/bin/uux -r - \
16570 ${substr_-5:$host}!rmail ${local_part}
16571 return_fail_output = true
16576 driver = manualroute
16578 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
16580 The file &_/usr/local/exim/uucphosts_& contains entries like
16582 darksite.ethereal.example: darksite.UUCP
16584 It can be set up more simply without adding and removing &".UUCP"& but this way
16585 makes clear the distinction between the domain name
16586 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
16588 .ecindex IIDmanrou1
16589 .ecindex IIDmanrou2
16598 . ////////////////////////////////////////////////////////////////////////////
16599 . ////////////////////////////////////////////////////////////////////////////
16601 .chapter "The queryprogram router" "CHAPdriverlast"
16602 .scindex IIDquerou1 "&(queryprogram)& router"
16603 .scindex IIDquerou2 "routers" "&(queryprogram)&"
16604 .cindex "routing" "by external program"
16605 The &(queryprogram)& router routes an address by running an external command
16606 and acting on its output. This is an expensive way to route, and is intended
16607 mainly for use in lightly-loaded systems, or for performing experiments.
16608 However, if it is possible to use the precondition options (&%domains%&,
16609 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
16610 be used in special cases, even on a busy host. There are the following private
16612 .cindex "options" "&(queryprogram)& router"
16614 .option command queryprogram string&!! unset
16615 This option must be set. It specifies the command that is to be run. The
16616 command is split up into a command name and arguments, and then each is
16617 expanded separately (exactly as for a &(pipe)& transport, described in chapter
16618 &<<CHAPpipetransport>>&).
16621 .option command_group queryprogram string unset
16622 .cindex "gid (group id)" "in &(queryprogram)& router"
16624 This option specifies a gid to be set when running the command while routing an
16625 address for deliver. It must be set if &%command_user%& specifies a numerical
16626 uid. If it begins with a digit, it is interpreted as the numerical value of the
16627 gid. Otherwise it is looked up using &[getgrnam()]&.
16631 .option command_user queryprogram string unset
16632 .cindex "uid (user id)" "for &(queryprogram)&"
16634 This option must be set. It specifies the uid which is set when running the
16635 command while routing an address for delivery. If the value begins with a digit,
16636 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
16637 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
16638 not set, a value for the gid also.
16640 &*Warning:*& Changing uid and gid is possible only when Exim is running as
16641 root, which it does during a normal delivery in a conventional configuration.
16642 However, when an address is being verified during message reception, Exim is
16643 usually running as the Exim user, not as root. If the &(queryprogram)& router
16644 is called from a non-root process, Exim cannot change uid or gid before running
16645 the command. In this circumstance the command runs under the current uid and
16650 .option current_directory queryprogram string /
16651 This option specifies an absolute path which is made the current directory
16652 before running the command.
16655 .option timeout queryprogram time 1h
16656 If the command does not complete within the timeout period, its process group
16657 is killed and the message is frozen. A value of zero time specifies no
16661 The standard output of the command is connected to a pipe, which is read when
16662 the command terminates. It should consist of a single line of output,
16663 containing up to five fields, separated by white space. The maximum length of
16664 the line is 1023 characters. Longer lines are silently truncated. The first
16665 field is one of the following words (case-insensitive):
16668 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
16671 &'Decline'&: the router declines; pass the address to the next router, unless
16672 &%no_more%& is set.
16674 &'Fail'&: routing failed; do not pass the address to any more routers. Any
16675 subsequent text on the line is an error message. If the router is run as part
16676 of address verification during an incoming SMTP message, the message is
16677 included in the SMTP response.
16679 &'Defer'&: routing could not be completed at this time; try again later. Any
16680 subsequent text on the line is an error message which is logged. It is not
16681 included in any SMTP response.
16683 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
16685 &'Pass'&: pass the address to the next router (or the router specified by
16686 &%pass_router%&), overriding &%no_more%&.
16688 &'Redirect'&: the message is redirected. The remainder of the line is a list of
16689 new addresses, which are routed independently, starting with the first router,
16690 or the router specified by &%redirect_router%&, if set.
16693 When the first word is &'accept'&, the remainder of the line consists of a
16694 number of keyed data values, as follows (split into two lines here, to fit on
16697 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
16698 LOOKUP=byname|bydns DATA=<text>
16700 The data items can be given in any order, and all are optional. If no transport
16701 is included, the transport specified by the generic &%transport%& option is
16702 used. The list of hosts and the lookup type are needed only if the transport is
16703 an &(smtp)& transport that does not itself supply a list of hosts.
16705 The format of the list of hosts is the same as for the &(manualroute)& router.
16706 As well as host names and IP addresses with optional port numbers, as described
16707 in section &<<SECTformatonehostitem>>&, it may contain names followed by
16708 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
16709 (see section &<<SECThostshowused>>&).
16711 If the lookup type is not specified, Exim behaves as follows when trying to
16712 find an IP address for each host: First, a DNS lookup is done. If this yields
16713 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
16714 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
16715 result of the lookup is the result of that call.
16717 .cindex "&$address_data$&"
16718 If the DATA field is set, its value is placed in the &$address_data$&
16719 variable. For example, this return line
16721 accept hosts=x1.y.example:x2.y.example data="rule1"
16723 routes the address to the default transport, passing a list of two hosts. When
16724 the transport runs, the string &"rule1"& is in &$address_data$&.
16725 .ecindex IIDquerou1
16726 .ecindex IIDquerou2
16731 . ////////////////////////////////////////////////////////////////////////////
16732 . ////////////////////////////////////////////////////////////////////////////
16734 .chapter "The redirect router" "CHAPredirect"
16735 .scindex IIDredrou1 "&(redirect)& router"
16736 .scindex IIDredrou2 "routers" "&(redirect)&"
16737 .cindex "alias file" "in a &(redirect)& router"
16738 .cindex "address redirection" "&(redirect)& router"
16739 The &(redirect)& router handles several kinds of address redirection. Its most
16740 common uses are for resolving local part aliases from a central alias file
16741 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
16742 files, but it has many other potential uses. The incoming address can be
16743 redirected in several different ways:
16746 It can be replaced by one or more new addresses which are themselves routed
16749 It can be routed to be delivered to a given file or directory.
16751 It can be routed to be delivered to a specified pipe command.
16753 It can cause an automatic reply to be generated.
16755 It can be forced to fail, with a custom error message.
16757 It can be temporarily deferred.
16759 It can be discarded.
16762 The generic &%transport%& option must not be set for &(redirect)& routers.
16763 However, there are some private options which define transports for delivery to
16764 files and pipes, and for generating autoreplies. See the &%file_transport%&,
16765 &%pipe_transport%& and &%reply_transport%& descriptions below.
16769 .section "Redirection data"
16770 The router operates by interpreting a text string which it obtains either by
16771 expanding the contents of the &%data%& option, or by reading the entire
16772 contents of a file whose name is given in the &%file%& option. These two
16773 options are mutually exclusive. The first is commonly used for handling system
16774 aliases, in a configuration like this:
16778 data = ${lookup{$local_part}lsearch{/etc/aliases}}
16780 If the lookup fails, the expanded string in this example is empty. When the
16781 expansion of &%data%& results in an empty string, the router declines. A forced
16782 expansion failure also causes the router to decline; other expansion failures
16783 cause delivery to be deferred.
16785 A configuration using &%file%& is commonly used for handling users'
16786 &_.forward_& files, like this:
16791 file = $home/.forward
16794 If the file does not exist, or causes no action to be taken (for example, it is
16795 empty or consists only of comments), the router declines. &*Warning*&: This
16796 is not the case when the file contains syntactically valid items that happen to
16797 yield empty addresses, for example, items containing only RFC 2822 address
16802 .section "Forward files and address verification"
16803 .cindex "address redirection" "while verifying"
16804 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
16805 &_.forward_& files, as in the example above. There are two reasons for this:
16808 When Exim is receiving an incoming SMTP message from a remote host, it is
16809 running under the Exim uid, not as root.
16810 No additional groups are set up, even if the Exim uid is a member of other
16811 groups (that is, the &[initgroups()]& function is not run).
16812 Exim is unable to change uid to read the file as the user, and it may not be
16813 able to read it as the Exim user. So in practice the router may not be able to
16816 However, even when the router can operate, the existence of a &_.forward_& file
16817 is unimportant when verifying an address. What should be checked is whether the
16818 local part is a valid user name or not. Cutting out the redirection processing
16819 saves some resources.
16827 .section "Interpreting redirection data"
16828 .cindex "Sieve filter" "specifying in redirection data"
16829 .cindex "filter" "specifying in redirection data"
16830 The contents of the data string, whether obtained from &%data%& or &%file%&,
16831 can be interpreted in two different ways:
16834 If the &%allow_filter%& option is set true, and the data begins with the text
16835 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
16836 &'filtering'& instructions in the form of an Exim or Sieve filter file,
16837 respectively. Details of the syntax and semantics of filter files are described
16838 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
16839 document is intended for use by end users.
16841 Otherwise, the data must be a comma-separated list of redirection items, as
16842 described in the next section.
16845 When a message is redirected to a file (a &"mail folder"&), the file name given
16846 in a non-filter redirection list must always be an absolute path. A filter may
16847 generate a relative path &-- how this is handled depends on the transport's
16848 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
16849 for the &(appendfile)& transport.
16853 .section "Items in a non-filter redirection list" "SECTitenonfilred"
16854 .cindex "address redirection" "non-filter list items"
16855 When the redirection data is not an Exim or Sieve filter, for example, if it
16856 comes from a conventional alias or forward file, it consists of a list of
16857 addresses, file names, pipe commands, or certain special items (see section
16858 &<<SECTspecitredli>>& below). The special items can be individually enabled or
16859 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
16860 depending on their default values. The items in the list are separated by
16861 commas or newlines.
16862 If a comma is required in an item, the entire item must be enclosed in double
16865 Lines starting with a # character are comments, and are ignored, and # may
16866 also appear following a comma, in which case everything between the # and the
16867 next newline character is ignored.
16869 If an item is entirely enclosed in double quotes, these are removed. Otherwise
16870 double quotes are retained because some forms of mail address require their use
16871 (but never to enclose the entire address). In the following description,
16872 &"item"& refers to what remains after any surrounding double quotes have been
16875 .cindex "&$local_part$&"
16876 &*Warning*&: If you use an Exim expansion to construct a redirection address,
16877 and the expansion contains a reference to &$local_part$&, you should make use
16878 of the &%quote_local_part%& expansion operator, in case the local part contains
16879 special characters. For example, to redirect all mail for the domain
16880 &'obsolete.example'&, retaining the existing local part, you could use this
16883 data = ${quote_local_part:$local_part}@newdomain.example
16887 .section "Redirecting to a local mailbox" "SECTredlocmai"
16888 .cindex "routing" "loops in"
16889 .cindex "loop while routing" "avoidance of"
16890 .cindex "address redirection" "to local mailbox"
16891 A redirection item may safely be the same as the address currently under
16892 consideration. This does not cause a routing loop, because a router is
16893 automatically skipped if any ancestor of the address that is being processed
16894 is the same as the current address and was processed by the current router.
16895 Such an address is therefore passed to the following routers, so it is handled
16896 as if there were no redirection. When making this loop-avoidance test, the
16897 complete local part, including any prefix or suffix, is used.
16899 .cindex "address redirection" "local part without domain"
16900 Specifying the same local part without a domain is a common usage in personal
16901 filter files when the user wants to have messages delivered to the local
16902 mailbox and also forwarded elsewhere. For example, the user whose login is
16903 &'cleo'& might have a &_.forward_& file containing this:
16905 cleo, cleopatra@egypt.example
16907 .cindex "backslash in alias file"
16908 .cindex "alias file" "backslash in"
16909 For compatibility with other MTAs, such unqualified local parts may be
16910 preceeded by &"\"&, but this is not a requirement for loop prevention. However,
16911 it does make a difference if more than one domain is being handled
16914 If an item begins with &"\"& and the rest of the item parses as a valid RFC
16915 2822 address that does not include a domain, the item is qualified using the
16916 domain of the incoming address. In the absence of a leading &"\"&, unqualified
16917 addresses are qualified using the value in &%qualify_recipient%&, but you can
16918 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
16920 Care must be taken if there are alias names for local users.
16921 Consider an MTA handling a single local domain where the system alias file
16926 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
16927 messages in the local mailbox, and also forward copies elsewhere. He creates
16930 Sam.Reman, spqr@reme.elsewhere.example
16932 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
16933 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
16934 second time round, because it has previously routed it,
16935 and the following routers presumably cannot handle the alias. The forward file
16936 should really contain
16938 spqr, spqr@reme.elsewhere.example
16940 but because this is such a common error, the &%check_ancestor%& option (see
16941 below) exists to provide a way to get round it. This is normally set on a
16942 &(redirect)& router that is handling users' &_.forward_& files.
16946 .section "Special items in redirection lists" "SECTspecitredli"
16947 In addition to addresses, the following types of item may appear in redirection
16948 lists (that is, in non-filter redirection data):
16951 .cindex "pipe" "in redirection list"
16952 .cindex "address redirection" "to pipe"
16953 An item is treated as a pipe command if it begins with &"|"& and does not parse
16954 as a valid RFC 2822 address that includes a domain. A transport for running the
16955 command must be specified by the &%pipe_transport%& option.
16956 Normally, either the router or the transport specifies a user and a group under
16957 which to run the delivery. The default is to use the Exim user and group.
16959 Single or double quotes can be used for enclosing the individual arguments of
16960 the pipe command; no interpretation of escapes is done for single quotes. If
16961 the command contains a comma character, it is necessary to put the whole item
16962 in double quotes, for example:
16964 "|/some/command ready,steady,go"
16966 since items in redirection lists are terminated by commas. Do not, however,
16967 quote just the command. An item such as
16969 |"/some/command ready,steady,go"
16971 is interpreted as a pipe with a rather strange command name, and no arguments.
16974 .cindex "file" "in redirection list"
16975 .cindex "address redirection" "to file"
16976 An item is interpreted as a path name if it begins with &"/"& and does not
16977 parse as a valid RFC 2822 address that includes a domain. For example,
16979 /home/world/minbari
16981 is treated as a file name, but
16983 /s=molari/o=babylon/@x400gate.way
16985 is treated as an address. For a file name, a transport must be specified using
16986 the &%file_transport%& option. However, if the generated path name ends with a
16987 forward slash character, it is interpreted as a directory name rather than a
16988 file name, and &%directory_transport%& is used instead.
16990 Normally, either the router or the transport specifies a user and a group under
16991 which to run the delivery. The default is to use the Exim user and group.
16993 .cindex "&_/dev/null_&"
16994 However, if a redirection item is the path &_/dev/null_&, delivery to it is
16995 bypassed at a high level, and the log entry shows &"**bypassed**"&
16996 instead of a transport name. In this case the user and group are not used.
16999 .cindex "included address list"
17000 .cindex "address redirection" "included external list"
17001 If an item is of the form
17003 :include:<path name>
17005 a list of further items is taken from the given file and included at that
17006 point. &*Note*&: Such a file can not be a filter file; it is just an
17007 out-of-line addition to the list. The items in the included list are separated
17008 by commas or newlines and are not subject to expansion. If this is the first
17009 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
17010 the alias name. This example is incorrect:
17012 list1 :include:/opt/lists/list1
17014 It must be given as
17016 list1: :include:/opt/lists/list1
17019 .cindex "address redirection" "to black hole"
17020 Sometimes you want to throw away mail to a particular local part. Making the
17021 &%data%& option expand to an empty string does not work, because that causes
17022 the router to decline. Instead, the alias item
17023 .cindex "black hole"
17024 .cindex "abandoning mail"
17028 can be used. It does what its name implies. No delivery is done, and no error
17029 message is generated. This has the same effect as specifing &_/dev/null_&, but
17030 can be independently disabled.
17032 &*Warning*&: If &`:blackhole:`& appears anywhere in a redirection list, no
17033 delivery is done for the original local part, even if other redirection items
17034 are present. If you are generating a multi-item list (for example, by reading a
17035 database) and need the ability to provide a no-op item, you must use
17039 .cindex "delivery" "forcing failure"
17040 .cindex "delivery" "forcing deferral"
17041 .cindex "failing delivery" "forcing"
17042 .cindex "deferred delivery" "forcing"
17043 .cindex "customizing" "failure message"
17044 An attempt to deliver a particular address can be deferred or forced to fail by
17045 redirection items of the form
17050 respectively. When a redirection list contains such an item, it applies to the
17051 entire redirection; any other items in the list are ignored (&':blackhole:'& is
17052 different). Any text following &':fail:'& or &':defer:'& is placed in the error
17053 text associated with the failure. For example, an alias file might contain:
17055 X.Employee: :fail: Gone away, no forwarding address
17057 In the case of an address that is being verified from an ACL or as the subject
17059 .cindex "VRFY error text" "display of"
17060 VRFY command, the text is included in the SMTP error response by
17062 .cindex "EXPN error text" "display of"
17063 The text is not included in the response to an EXPN command.
17065 .cindex "&$acl_verify_message$&"
17066 In an ACL, an explicitly provided message overrides the default, but the
17067 default message is available in the variable &$acl_verify_message$& and can
17068 therefore be included in a custom message if this is desired. Exim sends a 451
17069 SMTP code for a &':defer:'&, and 550 for &':fail:'&. In non-SMTP cases the text
17070 is included in the error message that Exim generates.
17072 Normally the error text is the rest of the redirection list &-- a comma does
17073 not terminate it &-- but a newline does act as a terminator. Newlines are not
17074 normally present in alias expansions. In &(lsearch)& lookups they are removed
17075 as part of the continuation process, but they may exist in other kinds of
17076 lookup and in &':include:'& files.
17078 During routing for message delivery (as opposed to verification), a redirection
17079 containing &':fail:'& causes an immediate failure of the incoming address,
17080 whereas &':defer:'& causes the message to remain on the queue so that a
17081 subsequent delivery attempt can happen at a later time. If an address is
17082 deferred for too long, it will ultimately fail, because the normal retry
17086 .cindex "alias file" "exception to default"
17087 Sometimes it is useful to use a single-key search type with a default (see
17088 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
17089 for exceptions to the default. These can be handled by aliasing them to
17093 This differs from &':fail:'& in that it causes the &(redirect)& router to
17094 decline, whereas &':fail:'& forces routing to fail. A lookup which results in
17095 an empty redirection list has the same effect.
17099 .section "Duplicate addresses"
17100 .cindex "duplicate addresses"
17101 .cindex "address duplicate" "discarding"
17102 .cindex "pipe" "duplicated"
17103 Exim removes duplicate addresses from the list to which it is delivering, so as
17104 to deliver just one copy to each address. This does not apply to deliveries
17105 routed to pipes by different immediate parent addresses, but an indirect
17106 aliasing scheme of the type
17108 pipe: |/some/command $local_part
17112 does not work with a message that is addressed to both local parts, because
17113 when the second is aliased to the intermediate local part &"pipe"& it gets
17114 discarded as being the same as a previously handled address. However, a scheme
17117 localpart1: |/some/command $local_part
17118 localpart2: |/some/command $local_part
17120 does result in two different pipe deliveries, because the immediate parents of
17121 the pipes are distinct.
17125 .section "Repeated redirection expansion"
17126 .cindex "repeated redirection expansion"
17127 .cindex "address redirection" "repeated for each delivery attempt"
17128 When a message cannot be delivered to all of its recipients immediately,
17129 leading to two or more delivery attempts, redirection expansion is carried out
17130 afresh each time for those addresses whose children were not all previously
17131 delivered. If redirection is being used as a mailing list, this can lead to new
17132 members of the list receiving copies of old messages. The &%one_time%& option
17133 can be used to avoid this.
17136 .section "Errors in redirection lists"
17137 .cindex "address redirection" "errors"
17138 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
17139 error is skipped, and an entry is written to the main log. This may be useful
17140 for mailing lists that are automatically managed. Otherwise, if an error is
17141 detected while generating the list of new addresses, the original address is
17142 deferred. See also &%syntax_errors_to%&.
17146 .section "Private options for the redirect router"
17148 .cindex "options" "&(redirect)& router"
17149 The private options for the &(redirect)& router are as follows:
17152 .option allow_defer redirect boolean false
17153 Setting this option allows the use of &':defer:'& in non-filter redirection
17154 data, or the &%defer%& command in an Exim filter file.
17157 .option allow_fail redirect boolean false
17158 .cindex "failing delivery" "from filter"
17159 If this option is true, the &':fail:'& item can be used in a redirection list,
17160 and the &%fail%& command may be used in an Exim filter file.
17163 .option allow_filter redirect boolean false
17164 .cindex "filter" "enabling use of"
17165 .cindex "Sieve filter" "enabling use of"
17166 Setting this option allows Exim to interpret redirection data that starts with
17167 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
17168 are some features of Exim filter files that some administrators may wish to
17169 lock out; see the &%forbid_filter_%&&'xxx'& options below.
17171 It is also possible to lock out Exim filters or Sieve filters while allowing
17172 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
17175 The filter is run using the uid and gid set by the generic &%user%& and
17176 &%group%& options. These take their defaults from the password data if
17177 &%check_local_user%& is set, so in the normal case of users' personal filter
17178 files, the filter is run as the relevant user. When &%allow_filter%& is set
17179 true, Exim insists that either &%check_local_user%& or &%user%& is set.
17183 .option allow_freeze redirect boolean false
17184 .cindex "freezing messages" "allowing in filter"
17185 Setting this option allows the use of the &%freeze%& command in an Exim filter.
17186 This command is more normally encountered in system filters, and is disabled by
17187 default for redirection filters because it isn't something you usually want to
17188 let ordinary users do.
17192 .option check_ancestor redirect boolean false
17193 This option is concerned with handling generated addresses that are the same
17194 as some address in the list of redirection ancestors of the current address.
17195 Although it is turned off by default in the code, it is set in the default
17196 configuration file for handling users' &_.forward_& files. It is recommended
17197 for this use of the &(redirect)& router.
17199 When &%check_ancestor%& is set, if a generated address (including the domain)
17200 is the same as any ancestor of the current address, it is replaced by a copy of
17201 the current address. This helps in the case where local part A is aliased to B,
17202 and B has a &_.forward_& file pointing back to A. For example, within a single
17203 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
17204 &_&~jb/.forward_& contains:
17206 \Joe.Bloggs, <other item(s)>
17208 Without the &%check_ancestor%& setting, either local part (&"jb"& or
17209 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
17210 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
17211 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
17212 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
17213 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
17214 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
17215 original address. See also the &%repeat_use%& option below.
17218 .option check_group redirect boolean "see below"
17219 When the &%file%& option is used, the group owner of the file is checked only
17220 when this option is set. The permitted groups are those listed in the
17221 &%owngroups%& option, together with the user's default group if
17222 &%check_local_user%& is set. If the file has the wrong group, routing is
17223 deferred. The default setting for this option is true if &%check_local_user%&
17224 is set and the &%modemask%& option permits the group write bit, or if the
17225 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
17229 .option check_owner redirect boolean "see below"
17230 When the &%file%& option is used, the owner of the file is checked only when
17231 this option is set. If &%check_local_user%& is set, the local user is
17232 permitted; otherwise the owner must be one of those listed in the &%owners%&
17233 option. The default value for this option is true if &%check_local_user%& or
17234 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
17237 .option data redirect string&!! unset
17238 This option is mutually exclusive with &%file%&. One or other of them must be
17239 set, but not both. The contents of &%data%& are expanded, and then used as the
17240 list of forwarding items, or as a set of filtering instructions. If the
17241 expansion is forced to fail, or the result is an empty string or a string that
17242 has no effect (consists entirely of comments), the router declines.
17244 When filtering instructions are used, the string must begin with &"#Exim
17245 filter"&, and all comments in the string, including this initial one, must be
17246 terminated with newline characters. For example:
17248 data = #Exim filter\n\
17249 if $h_to: contains Exim then save $home/mail/exim endif
17251 If you are reading the data from a database where newlines cannot be included,
17252 you can use the &${sg}$& expansion item to turn the escape string of your
17253 choice into a newline.
17256 .option directory_transport redirect string&!! unset
17257 A &(redirect)& router sets up a direct delivery to a directory when a path name
17258 ending with a slash is specified as a new &"address"&. The transport used is
17259 specified by this option, which, after expansion, must be the name of a
17260 configured transport. This should normally be an &(appendfile)& transport.
17263 .option file redirect string&!! unset
17264 This option specifies the name of a file that contains the redirection data. It
17265 is mutually exclusive with the &%data%& option. The string is expanded before
17266 use; if the expansion is forced to fail, the router declines. Other expansion
17267 failures cause delivery to be deferred. The result of a successful expansion
17268 must be an absolute path. The entire file is read and used as the redirection
17269 data. If the data is an empty string or a string that has no effect (consists
17270 entirely of comments), the router declines.
17272 .cindex "NFS" "checking for file existence"
17273 If the attempt to open the file fails with a &"does not exist"& error, Exim
17274 runs a check on the containing directory,
17275 unless &%ignore_enotdir%& is true (see below).
17276 If the directory does not appear to exist, delivery is deferred. This can
17277 happen when users' &_.forward_& files are in NFS-mounted directories, and there
17278 is a mount problem. If the containing directory does exist, but the file does
17279 not, the router declines.
17282 .option file_transport redirect string&!! unset
17283 .cindex "&$address_file$&"
17284 A &(redirect)& router sets up a direct delivery to a file when a path name not
17285 ending in a slash is specified as a new &"address"&. The transport used is
17286 specified by this option, which, after expansion, must be the name of a
17287 configured transport. This should normally be an &(appendfile)& transport. When
17288 it is running, the file name is in &$address_file$&.
17291 .option forbid_blackhole redirect boolean false
17292 If this option is true, the &':blackhole:'& item may not appear in a
17296 .option forbid_exim_filter redirect boolean false
17297 If this option is set true, only Sieve filters are permitted when
17298 &%allow_filter%& is true.
17303 .option forbid_file redirect boolean false
17304 .cindex "delivery" "to file; forbidding"
17305 .cindex "Sieve filter" "forbidding delivery to a file"
17306 .cindex "Sieve filter" "&""keep""& facility; disabling"
17307 If this option is true, this router may not generate a new address that
17308 specifies delivery to a local file or directory, either from a filter or from a
17309 conventional forward file. This option is forced to be true if &%one_time%& is
17310 set. It applies to Sieve filters as well as to Exim filters, but if true, it
17311 locks out the Sieve's &"keep"& facility.
17314 .option forbid_filter_dlfunc redirect boolean false
17315 .cindex "filter" "locking out certain features"
17316 If this option is true, string expansions in Exim filters are not allowed to
17317 make use of the &%dlfunc%& expansion facility to run dynamically loaded
17320 .option forbid_filter_existstest redirect boolean false
17321 .cindex "expansion" "statting a file"
17322 If this option is true, string expansions in Exim filters are not allowed to
17323 make use of the &%exists%& condition or the &%stat%& expansion item.
17325 .option forbid_filter_logwrite redirect boolean false
17326 If this option is true, use of the logging facility in Exim filters is not
17327 permitted. Logging is in any case available only if the filter is being run
17328 under some unprivileged uid (which is normally the case for ordinary users'
17329 &_.forward_& files).
17332 .option forbid_filter_lookup redirect boolean false
17333 If this option is true, string expansions in Exim filter files are not allowed
17334 to make use of &%lookup%& items.
17337 .option forbid_filter_perl redirect boolean false
17338 This option has an effect only if Exim is built with embedded Perl support. If
17339 it is true, string expansions in Exim filter files are not allowed to make use
17340 of the embedded Perl support.
17343 .option forbid_filter_readfile redirect boolean false
17344 If this option is true, string expansions in Exim filter files are not allowed
17345 to make use of &%readfile%& items.
17348 .option forbid_filter_readsocket redirect boolean false
17349 If this option is true, string expansions in Exim filter files are not allowed
17350 to make use of &%readsocket%& items.
17353 .option forbid_filter_reply redirect boolean false
17354 If this option is true, this router may not generate an automatic reply
17355 message. Automatic replies can be generated only from Exim or Sieve filter
17356 files, not from traditional forward files. This option is forced to be true if
17357 &%one_time%& is set.
17360 .option forbid_filter_run redirect boolean false
17361 If this option is true, string expansions in Exim filter files are not allowed
17362 to make use of &%run%& items.
17365 .option forbid_include redirect boolean false
17366 If this option is true, items of the form
17368 :include:<path name>
17370 are not permitted in non-filter redirection lists.
17373 .option forbid_pipe redirect boolean false
17374 .cindex "delivery" "to pipe; forbidding"
17375 If this option is true, this router may not generate a new address which
17376 specifies delivery to a pipe, either from an Exim filter or from a conventional
17377 forward file. This option is forced to be true if &%one_time%& is set.
17380 .option forbid_sieve_filter redirect boolean false
17381 If this option is set true, only Exim filters are permitted when
17382 &%allow_filter%& is true.
17387 .option hide_child_in_errmsg redirect boolean false
17388 .cindex "bounce message" "redirection details; suppressing"
17389 If this option is true, it prevents Exim from quoting a child address if it
17390 generates a bounce or delay message for it. Instead it says &"an address
17391 generated from <&'the top level address'&>"&. Of course, this applies only to
17392 bounces generated locally. If a message is forwarded to another host, &'its'&
17393 bounce may well quote the generated address.
17396 .option ignore_eacces redirect boolean false
17398 If this option is set and an attempt to open a redirection file yields the
17399 EACCES error (permission denied), the &(redirect)& router behaves as if the
17400 file did not exist.
17403 .option ignore_enotdir redirect boolean false
17405 If this option is set and an attempt to open a redirection file yields the
17406 ENOTDIR error (something on the path is not a directory), the &(redirect)&
17407 router behaves as if the file did not exist.
17409 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
17410 router that has the &%file%& option set discovers that the file does not exist
17411 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
17412 against unmounted NFS directories. If the parent can not be statted, delivery
17413 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
17414 is set, because that option tells Exim to ignore &"something on the path is not
17415 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
17416 that some operating systems give ENOENT where others give ENOTDIR.
17420 .option include_directory redirect string unset
17421 If this option is set, the path names of any &':include:'& items in a
17422 redirection list must start with this directory.
17425 .option modemask redirect "octal integer" 022
17426 This specifies mode bits which must not be set for a file specified by the
17427 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
17430 .option one_time redirect boolean false
17431 .cindex "one-time aliasing/forwarding expansion"
17432 .cindex "alias file" "one-time expansion"
17433 .cindex "forward file" "one-time expansion"
17434 .cindex "mailing lists" "one-time expansion"
17435 .cindex "address redirection" "one-time expansion"
17436 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
17437 files each time it tries to deliver a message causes a problem when one or more
17438 of the generated addresses fails be delivered at the first attempt. The problem
17439 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
17440 but of what happens when the redirection list changes during the time that the
17441 message is on Exim's queue. This is particularly true in the case of mailing
17442 lists, where new subscribers might receive copies of messages that were posted
17443 before they subscribed.
17445 If &%one_time%& is set and any addresses generated by the router fail to
17446 deliver at the first attempt, the failing addresses are added to the message as
17447 &"top level"& addresses, and the parent address that generated them is marked
17448 &"delivered"&. Thus, redirection does not happen again at the next delivery
17451 &*Warning 1*&: Any header line addition or removal that is specified by this
17452 router would be lost if delivery did not succeed at the first attempt. For this
17453 reason, the &%headers_add%& and &%headers_remove%& generic options are not
17454 permitted when &%one_time%& is set.
17456 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
17457 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
17458 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
17460 &*Warning 3*&: The &%unseen%& generic router option may not be set with
17463 The original top-level address is remembered with each of the generated
17464 addresses, and is output in any log messages. However, any intermediate parent
17465 addresses are not recorded. This makes a difference to the log only if
17466 &%all_parents%& log selector is set. It is expected that &%one_time%& will
17467 typically be used for mailing lists, where there is normally just one level of
17471 .option owners redirect "string list" unset
17472 .cindex "ownership" "alias file"
17473 .cindex "ownership" "forward file"
17474 .cindex "alias file" "ownership"
17475 .cindex "forward file" "ownership"
17476 This specifies a list of permitted owners for the file specified by &%file%&.
17477 This list is in addition to the local user when &%check_local_user%& is set.
17478 See &%check_owner%& above.
17481 .option owngroups redirect "string list" unset
17482 This specifies a list of permitted groups for the file specified by &%file%&.
17483 The list is in addition to the local user's primary group when
17484 &%check_local_user%& is set. See &%check_group%& above.
17487 .option pipe_transport redirect string&!! unset
17488 .cindex "&$address_pipe$&"
17489 A &(redirect)& router sets up a direct delivery to a pipe when a string
17490 starting with a vertical bar character is specified as a new &"address"&. The
17491 transport used is specified by this option, which, after expansion, must be the
17492 name of a configured transport. This should normally be a &(pipe)& transport.
17493 When the transport is run, the pipe command is in &$address_pipe$&.
17496 .option qualify_domain redirect string&!! unset
17497 .cindex "&$qualify_recipient$&"
17499 If this option is set, and an unqualified address (one without a domain) is
17500 generated, and that address would normally be qualified by the global setting
17501 in &%qualify_recipient%&, it is instead qualified with the domain specified by
17502 expanding this string. If the expansion fails, the router declines. If you want
17503 to revert to the default, you can have the expansion generate
17504 &$qualify_recipient$&.
17506 This option applies to all unqualified addresses generated by Exim filters,
17507 but for traditional &_.forward_& files, it applies only to addresses that are
17508 not preceded by a backslash. Sieve filters cannot generate unqualified
17512 .option qualify_preserve_domain redirect boolean false
17513 .cindex "domain" "in redirection; preserving"
17514 .cindex "preserving domain in redirection"
17515 .cindex "address redirection" "domain; preserving"
17517 If this option is set, the router's local &%qualify_domain%& option must not be
17518 set (a configuration error occurs if it is). If an unqualified address (one
17519 without a domain) is generated, it is qualified with the domain of the parent
17520 address (the immediately preceding ancestor) instead of the global
17521 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
17522 this applies whether or not the address is preceded by a backslash.
17526 .option repeat_use redirect boolean true
17527 If this option is set false, the router is skipped for a child address that has
17528 any ancestor that was routed by this router. This test happens before any of
17529 the other preconditions are tested. Exim's default anti-looping rules skip
17530 only when the ancestor is the same as the current address. See also
17531 &%check_ancestor%& above and the generic &%redirect_router%& option.
17534 .option reply_transport redirect string&!! unset
17535 A &(redirect)& router sets up an automatic reply when a &%mail%& or
17536 &%vacation%& command is used in a filter file. The transport used is specified
17537 by this option, which, after expansion, must be the name of a configured
17538 transport. This should normally be an &(autoreply)& transport. Other transports
17539 are unlikely to do anything sensible or useful.
17542 .option rewrite redirect boolean true
17543 .cindex "address redirection" "disabling rewriting"
17544 If this option is set false, addresses generated by the router are not
17545 subject to address rewriting. Otherwise, they are treated like new addresses
17546 and are rewritten according to the global rewriting rules.
17549 .option sieve_subaddress redirect string&!! unset
17550 The value of this option is passed to a Sieve filter to specify the
17551 :subaddress part of an address.
17553 .option sieve_useraddress redirect string&!! unset
17554 The value of this option is passed to a Sieve filter to specify the :user part
17555 of an address. However, if it is unset, the entire original local part
17556 (including any prefix or suffix) is used for :user.
17559 .option sieve_vacation_directory redirect string&!! unset
17560 .cindex "Sieve filter" "vacation directory"
17561 To enable the &"vacation"& extension for Sieve filters, you must set
17562 &%sieve_vacation_directory%& to the directory where vacation databases are held
17563 (do not put anything else in that directory), and ensure that the
17564 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
17565 needs their own directory; Exim will create it if necessary.
17569 .option skip_syntax_errors redirect boolean false
17570 .cindex "forward file" "broken"
17571 .cindex "address redirection" "broken files"
17572 .cindex "alias file" "broken"
17573 .cindex "broken alias or forward files"
17574 .cindex "ignoring faulty addresses"
17575 .cindex "skipping faulty addresses"
17576 .cindex "error" "skipping bad syntax"
17577 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
17578 non-filter redirection data are skipped, and each failing address is logged. If
17579 &%syntax_errors_to%& is set, a message is sent to the address it defines,
17580 giving details of the failures. If &%syntax_errors_text%& is set, its contents
17581 are expanded and placed at the head of the error message generated by
17582 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
17583 be the same address as the generic &%errors_to%& option. The
17584 &%skip_syntax_errors%& option is often used when handling mailing lists.
17586 If all the addresses in a redirection list are skipped because of syntax
17587 errors, the router declines to handle the original address, and it is passed to
17588 the following routers.
17590 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
17591 error in the filter causes filtering to be abandoned without any action being
17592 taken. The incident is logged, and the router declines to handle the address,
17593 so it is passed to the following routers.
17595 .cindex "Sieve filter" "syntax errors in"
17596 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
17597 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
17598 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
17600 &%skip_syntax_errors%& can be used to specify that errors in users' forward
17601 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
17602 option, used with an address that does not get redirected, can be used to
17603 notify users of these errors, by means of a router like this:
17609 file = $home/.forward
17610 file_transport = address_file
17611 pipe_transport = address_pipe
17612 reply_transport = address_reply
17615 syntax_errors_to = real-$local_part@$domain
17616 syntax_errors_text = \
17617 This is an automatically generated message. An error has\n\
17618 been found in your .forward file. Details of the error are\n\
17619 reported below. While this error persists, you will receive\n\
17620 a copy of this message for every message that is addressed\n\
17621 to you. If your .forward file is a filter file, or if it is\n\
17622 a non-filter file containing no valid forwarding addresses,\n\
17623 a copy of each incoming message will be put in your normal\n\
17624 mailbox. If a non-filter file contains at least one valid\n\
17625 forwarding address, forwarding to the valid addresses will\n\
17626 happen, and those will be the only deliveries that occur.
17628 You also need a router to ensure that local addresses that are prefixed by
17629 &`real-`& are recognized, but not forwarded or filtered. For example, you could
17630 put this immediately before the &(userforward)& router:
17635 local_part_prefix = real-
17636 transport = local_delivery
17639 .option syntax_errors_text redirect string&!! unset
17640 See &%skip_syntax_errors%& above.
17643 .option syntax_errors_to redirect string unset
17644 See &%skip_syntax_errors%& above.
17645 .ecindex IIDredrou1
17646 .ecindex IIDredrou2
17653 . ////////////////////////////////////////////////////////////////////////////
17654 . ////////////////////////////////////////////////////////////////////////////
17656 .chapter "Environment for running local transports" "CHAPenvironment" &&&
17657 "Environment for local transports"
17658 .scindex IIDenvlotra1 "local transports" "environment for"
17659 .scindex IIDenvlotra2 "environment for local transports"
17660 .scindex IIDenvlotra3 "transport" "local; environment for"
17661 Local transports handle deliveries to files and pipes. (The &(autoreply)&
17662 transport can be thought of as similar to a pipe.) Exim always runs transports
17663 in subprocesses, under specified uids and gids. Typical deliveries to local
17664 mailboxes run under the uid and gid of the local user.
17666 Exim also sets a specific current directory while running the transport; for
17667 some transports a home directory setting is also relevant. The &(pipe)&
17668 transport is the only one that sets up environment variables; see section
17669 &<<SECTpipeenv>>& for details.
17671 The values used for the uid, gid, and the directories may come from several
17672 different places. In many cases, the router that handles the address associates
17673 settings with that address as a result of its &%check_local_user%&, &%group%&,
17674 or &%user%& options. However, values may also be given in the transport's own
17675 configuration, and these override anything that comes from the router.
17679 .section "Concurrent deliveries"
17680 .cindex "concurrent deliveries"
17681 .cindex "simultaneous deliveries"
17682 If two different messages for the same local recpient arrive more or less
17683 simultaneously, the two delivery processes are likely to run concurrently. When
17684 the &(appendfile)& transport is used to write to a file, Exim applies locking
17685 rules to stop concurrent processes from writing to the same file at the same
17688 However, when you use a &(pipe)& transport, it is up to you to arrange any
17689 locking that is needed. Here is a silly example:
17693 command = /bin/sh -c 'cat >>/some/file'
17695 This is supposed to write the message at the end of the file. However, if two
17696 messages arrive at the same time, the file will be scrambled. You can use the
17697 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
17698 file using the same algorithm that Exim itself uses.
17703 .section "Uids and gids" "SECTenvuidgid"
17704 .cindex "local transports" "uid and gid"
17705 .cindex "transport" "local; uid and gid"
17706 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
17707 overrides any group that the router set in the address, even if &%user%& is not
17708 set for the transport. This makes it possible, for example, to run local mail
17709 delivery under the uid of the recipient (set by the router), but in a special
17710 group (set by the transport). For example:
17713 # User/group are set by check_local_user in this router
17717 transport = group_delivery
17720 # This transport overrides the group
17722 driver = appendfile
17723 file = /var/spool/mail/$local_part
17726 If &%user%& is set for a transport, its value overrides what is set in the
17727 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
17728 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
17731 .cindex "&%initgroups%& option"
17732 When the uid is taken from the transport's configuration, the &[initgroups()]&
17733 function is called for the groups associated with that uid if the
17734 &%initgroups%& option is set for the transport. When the uid is not specified
17735 by the transport, but is associated with the address by a router, the option
17736 for calling &[initgroups()]& is taken from the router configuration.
17738 .cindex "&(pipe)& transport" "uid for"
17739 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
17740 is set and &%user%& is not set, the uid of the process that called Exim to
17741 receive the message is used, and if &%group%& is not set, the corresponding
17742 original gid is also used.
17744 This is the detailed preference order for obtaining a gid; the first of the
17745 following that is set is used:
17748 A &%group%& setting of the transport;
17750 A &%group%& setting of the router;
17752 A gid associated with a user setting of the router, either as a result of
17753 &%check_local_user%& or an explicit non-numeric &%user%& setting;
17755 The group associated with a non-numeric &%user%& setting of the transport;
17757 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
17758 the uid is the creator's uid;
17760 The Exim gid if the Exim uid is being used as a default.
17763 If, for example, the user is specified numerically on the router and there are
17764 no group settings, no gid is available. In this situation, an error occurs.
17765 This is different for the uid, for which there always is an ultimate default.
17766 The first of the following that is set is used:
17769 A &%user%& setting of the transport;
17771 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
17773 A &%user%& setting of the router;
17775 A &%check_local_user%& setting of the router;
17780 Of course, an error will still occur if the uid that is chosen is on the
17781 &%never_users%& list.
17787 .section "Current and home directories"
17788 .cindex "current directory for local transport"
17789 .cindex "home directory" "for local transport"
17790 .cindex "transport" "local; home directory for"
17791 .cindex "transport" "local; current directory for"
17792 Routers may set current and home directories for local transports by means of
17793 the &%transport_current_directory%& and &%transport_home_directory%& options.
17794 However, if the transport's &%current_directory%& or &%home_directory%& options
17795 are set, they override the router's values. In detail, the home directory
17796 for a local transport is taken from the first of these values that is set:
17799 The &%home_directory%& option on the transport;
17801 The &%transport_home_directory%& option on the router;
17803 The password data if &%check_local_user%& is set on the router;
17805 The &%router_home_directory%& option on the router.
17808 The current directory is taken from the first of these values that is set:
17811 The &%current_directory%& option on the transport;
17813 The &%transport_current_directory%& option on the router.
17817 If neither the router nor the transport sets a current directory, Exim uses the
17818 value of the home directory, if it is set. Otherwise it sets the current
17819 directory to &_/_& before running a local transport.
17823 .section "Expansion variables derived from the address"
17824 .cindex "&$domain$&"
17825 .cindex "&$local_part$&"
17826 .cindex "&$original_domain$&"
17827 Normally a local delivery is handling a single address, and in that case the
17828 variables such as &$domain$& and &$local_part$& are set during local
17829 deliveries. However, in some circumstances more than one address may be handled
17830 at once (for example, while writing batch SMTP for onward transmission by some
17831 other means). In this case, the variables associated with the local part are
17832 never set, &$domain$& is set only if all the addresses have the same domain,
17833 and &$original_domain$& is never set.
17834 .ecindex IIDenvlotra1
17835 .ecindex IIDenvlotra2
17836 .ecindex IIDenvlotra3
17844 . ////////////////////////////////////////////////////////////////////////////
17845 . ////////////////////////////////////////////////////////////////////////////
17847 .chapter "Generic options for transports" "CHAPtransportgeneric"
17848 .scindex IIDgenoptra1 "generic options" "transport"
17849 .scindex IIDgenoptra2 "options" "generic; for transports"
17850 .scindex IIDgenoptra3 "transport" "generic options for"
17851 The following generic options apply to all transports:
17854 .option body_only transports boolean false
17855 .cindex "transport" "body only"
17856 .cindex "message" "transporting body only"
17857 .cindex "body of message" "transporting"
17858 If this option is set, the message's headers are not transported. It is
17859 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
17860 or &(pipe)& transports, the settings of &%message_prefix%& and
17861 &%message_suffix%& should be checked, because this option does not
17862 automatically suppress them.
17865 .option current_directory transports string&!! unset
17866 .cindex "transport" "current directory for"
17867 This specifies the current directory that is to be set while running the
17868 transport, overriding any value that may have been set by the router.
17869 If the expansion fails for any reason, including forced failure, an error is
17870 logged, and delivery is deferred.
17873 .option disable_logging transports boolean false
17874 If this option is set true, nothing is logged for any
17875 deliveries by the transport or for any
17876 transport errors. You should not set this option unless you really, really know
17877 what you are doing.
17880 .option debug_print transports string&!! unset
17881 .cindex "testing" "variables in drivers"
17882 If this option is set and debugging is enabled (see the &%-d%& command line
17883 option), the string is expanded and included in the debugging output when the
17885 If expansion of the string fails, the error message is written to the debugging
17886 output, and Exim carries on processing.
17887 This facility is provided to help with checking out the values of variables and
17888 so on when debugging driver configurations. For example, if a &%headers_add%&
17889 option is not working properly, &%debug_print%& could be used to output the
17890 variables it references. A newline is added to the text if it does not end with
17894 .option delivery_date_add transports boolean false
17895 .cindex "&'Delivery-date:'& header line"
17896 If this option is true, a &'Delivery-date:'& header is added to the message.
17897 This gives the actual time the delivery was made. As this is not a standard
17898 header, Exim has a configuration option (&%delivery_date_remove%&) which
17899 requests its removal from incoming messages, so that delivered messages can
17900 safely be resent to other recipients.
17903 .option driver transports string unset
17904 This specifies which of the available transport drivers is to be used.
17905 There is no default, and this option must be set for every transport.
17908 .option envelope_to_add transports boolean false
17909 .cindex "&'Envelope-to:'& header line"
17910 If this option is true, an &'Envelope-to:'& header is added to the message.
17911 This gives the original address(es) in the incoming envelope that caused this
17912 delivery to happen. More than one address may be present if the transport is
17913 configured to handle several addresses at once, or if more than one original
17914 address was redirected to the same final address. As this is not a standard
17915 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
17916 its removal from incoming messages, so that delivered messages can safely be
17917 resent to other recipients.
17920 .option group transports string&!! "Exim group"
17921 .cindex "transport" "group; specifying"
17922 This option specifies a gid for running the transport process, overriding any
17923 value that the router supplies, and also overriding any value associated with
17924 &%user%& (see below).
17927 .option headers_add transports string&!! unset
17928 .cindex "header lines" "adding in transport"
17929 .cindex "transport" "header lines; adding"
17930 This option specifies a string of text that is expanded and added to the header
17931 portion of a message as it is transported, as described in section
17932 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
17933 routers. If the result of the expansion is an empty string, or if the expansion
17934 is forced to fail, no action is taken. Other expansion failures are treated as
17935 errors and cause the delivery to be deferred.
17939 .option headers_only transports boolean false
17940 .cindex "transport" "header lines only"
17941 .cindex "message" "transporting headers only"
17942 .cindex "header lines" "transporting"
17943 If this option is set, the message's body is not transported. It is mutually
17944 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
17945 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
17946 checked, since this option does not automatically suppress them.
17949 .option headers_remove transports string&!! unset
17950 .cindex "header lines" "removing"
17951 .cindex "transport" "header lines; removing"
17952 This option specifies a string that is expanded into a list of header names;
17953 these headers are omitted from the message as it is transported, as described
17954 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
17955 routers. If the result of the expansion is an empty string, or if the expansion
17956 is forced to fail, no action is taken. Other expansion failures are treated as
17957 errors and cause the delivery to be deferred.
17961 .option headers_rewrite transports string unset
17962 .cindex "transport" "header lines; rewriting"
17963 .cindex "rewriting" "at transport time"
17964 This option allows addresses in header lines to be rewritten at transport time,
17965 that is, as the message is being copied to its destination. The contents of the
17966 option are a colon-separated list of rewriting rules. Each rule is in exactly
17967 the same form as one of the general rewriting rules that are applied when a
17968 message is received. These are described in chapter &<<CHAPrewrite>>&. For
17971 headers_rewrite = a@b c@d f : \
17974 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
17975 &'w@z'& in all address-bearing header lines. The rules are applied to the
17976 header lines just before they are written out at transport time, so they affect
17977 only those copies of the message that pass through the transport. However, only
17978 the message's original header lines, and any that were added by a system
17979 filter, are rewritten. If a router or transport adds header lines, they are not
17980 affected by this option. These rewriting rules are &'not'& applied to the
17981 envelope. You can change the return path using &%return_path%&, but you cannot
17982 change envelope recipients at this time.
17985 .option home_directory transports string&!! unset
17986 .cindex "transport" "home directory for"
17988 This option specifies a home directory setting for &new("a local") transport,
17989 overriding any value that may be set by the router. The home directory is
17990 placed in &$home$& while expanding the transport's private options. It is also
17991 used as the current directory if no current directory is set by the
17992 &%current_directory%& option on the transport or the
17993 &%transport_current_directory%& option on the router. If the expansion fails
17994 for any reason, including forced failure, an error is logged, and delivery is
17998 .option initgroups transports boolean false
17999 .cindex "additional groups"
18000 .cindex "groups" "additional"
18001 .cindex "transport" "group; additional"
18002 If this option is true and the uid for the delivery process is provided by the
18003 transport, the &[initgroups()]& function is called when running the transport
18004 to ensure that any additional groups associated with the uid are set up.
18007 .option message_size_limit transports string&!! 0
18008 .cindex "limit" "message size per transport"
18009 .cindex "size of message" "limit"
18010 .cindex "transport" "message size; limiting"
18011 This option controls the size of messages passed through the transport. It is
18012 expanded before use; the result of the expansion must be a sequence of digits,
18013 optionally followed by K or M.
18014 If the expansion fails for any reason, including forced failure, or if the
18015 result is not of the required form, delivery is deferred.
18016 If the value is greater than zero and the size of a message exceeds this
18017 limit, the address is failed. If there is any chance that the resulting bounce
18018 message could be routed to the same transport, you should ensure that
18019 &%return_size_limit%& is less than the transport's &%message_size_limit%&, as
18020 otherwise the bounce message will fail to get delivered.
18024 .option rcpt_include_affixes transports boolean false
18025 .cindex "prefix" "for local part; including in envelope"
18026 .cindex "suffix" "for local part; including in envelope"
18027 .cindex "local part" "prefix"
18028 .cindex "local part" "suffix"
18029 When this option is false (the default), and an address that has had any
18030 affixes (prefixes or suffixes) removed from the local part is delivered by any
18031 form of SMTP or LMTP, the affixes are not included. For example, if a router
18034 local_part_prefix = *-
18036 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
18039 RCPT TO:<xyz@some.domain>
18041 This is also the case when an ACL-time callout is being used to verify a
18042 recipient address. However, if &%rcpt_include_affixes%& is set true, the
18043 whole local part is included in the RCPT command. This option applies to BSMTP
18044 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
18045 &(lmtp)& and &(smtp)& transports.
18048 .option retry_use_local_part transports boolean "see below"
18049 .cindex "hints database" "retry keys"
18050 When a delivery suffers a temporary failure, a retry record is created
18051 in Exim's hints database. For remote deliveries, the key for the retry record
18052 is based on the name and/or IP address of the failing remote host. For local
18053 deliveries, the key is normally the entire address, including both the local
18054 part and the domain. This is suitable for most common cases of local delivery
18055 temporary failure &-- for example, exceeding a mailbox quota should delay only
18056 deliveries to that mailbox, not to the whole domain.
18058 However, in some special cases you may want to treat a temporary local delivery
18059 as a failure associated with the domain, and not with a particular local part.
18060 (For example, if you are storing all mail for some domain in files.) You can do
18061 this by setting &%retry_use_local_part%& false.
18063 For all the local transports, its default value is true. For remote transports,
18064 the default value is false for tidiness, but changing the value has no effect
18065 on a remote transport in the current implementation.
18068 .option return_path transports string&!! unset
18069 .cindex "envelope sender"
18070 .cindex "transport" "return path; changing"
18071 .cindex "return path" "changing in transport"
18072 If this option is set, the string is expanded at transport time and replaces
18073 the existing return path (envelope sender) value in the copy of the message
18074 that is being delivered. An empty return path is permitted. This feature is
18075 designed for remote deliveries, where the value of this option is used in the
18076 SMTP MAIL command. If you set &%return_path%& for a local transport, the
18077 only effect is to change the address that is placed in the &'Return-path:'&
18078 header line, if one is added to the message (see the next option).
18080 .cindex "&$return_path$&"
18081 The expansion can refer to the existing value via &$return_path$&. This is
18082 either the message's envelope sender, or an address set by the
18083 &%errors_to%& option on a router. If the expansion is forced to fail, no
18084 replacement occurs; if it fails for another reason, delivery is deferred. This
18085 option can be used to support VERP (Variable Envelope Return Paths) &-- see
18086 section &<<SECTverp>>&.
18089 &*Note*&: If a delivery error is detected locally, including the case when a
18090 remote server rejects a message at SMTP time, the bounce message is not sent to
18091 the value of this option. It is sent to the previously set errors address.
18092 This defaults to the incoming sender address, but can be changed by setting
18093 &%errors_to%& in a router.
18098 .option return_path_add transports boolean false
18099 .cindex "&'Return-path:'& header line"
18100 If this option is true, a &'Return-path:'& header is added to the message.
18101 Although the return path is normally available in the prefix line of BSD
18102 mailboxes, this is commonly not displayed by MUAs, and so the user does not
18103 have easy access to it.
18105 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
18106 the delivery SMTP server makes the final delivery"&. This implies that this
18107 header should not be present in incoming messages. Exim has a configuration
18108 option, &%return_path_remove%&, which requests removal of this header from
18109 incoming messages, so that delivered messages can safely be resent to other
18113 .option shadow_condition transports string&!! unset
18114 See &%shadow_transport%& below.
18117 .option shadow_transport transports string unset
18118 .cindex "shadow transport"
18119 .cindex "transport" "shadow"
18120 A local transport may set the &%shadow_transport%& option to the name of
18121 another local transport. Shadow remote transports are not supported.
18123 Whenever a delivery to the main transport succeeds, and either
18124 &%shadow_condition%& is unset, or its expansion does not result in the empty
18125 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
18126 passed to the shadow transport, with the same delivery address or addresses. If
18127 expansion fails, no action is taken except that non-forced expansion failures
18128 cause a log line to be written.
18130 The result of the shadow transport is discarded and does not affect the
18131 subsequent processing of the message. Only a single level of shadowing is
18132 provided; the &%shadow_transport%& option is ignored on any transport when it
18133 is running as a shadow. Options concerned with output from pipes are also
18134 ignored. The log line for the successful delivery has an item added on the end,
18137 ST=<shadow transport name>
18139 If the shadow transport did not succeed, the error message is put in
18140 parentheses afterwards. Shadow transports can be used for a number of different
18141 purposes, including keeping more detailed log information than Exim normally
18142 provides, and implementing automatic acknowledgement policies based on message
18143 headers that some sites insist on.
18146 .option transport_filter transports string&!! unset
18147 .cindex "transport" "filter"
18148 .cindex "filter" "transport filter"
18149 This option sets up a filtering (in the Unix shell sense) process for messages
18150 at transport time. It should not be confused with mail filtering as set up by
18151 individual users or via a system filter.
18153 When the message is about to be written out, the command specified by
18154 &%transport_filter%& is started up in a separate, parallel process, and
18155 the entire message, including the header lines, is passed to it on its standard
18156 input (this in fact is done from a third process, to avoid deadlock). The
18157 command must be specified as an absolute path.
18159 The lines of the message that are written to the transport filter are
18160 terminated by newline (&"\n"&). The message is passed to the filter before any
18161 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
18162 lines beginning with a dot, and also before any processing implied by the
18163 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
18164 &(pipe)& transports.
18166 The standard error for the filter process is set to the same destination as its
18167 standard output; this is read and written to the message's ultimate
18168 destination. The process that writes the message to the filter, the
18169 filter itself, and the original process that reads the result and delivers it
18170 are all run in parallel, like a shell pipeline.
18172 The filter can perform any transformations it likes, but of course should take
18173 care not to break RFC 2822 syntax. A demonstration Perl script is provided in
18174 &_util/transport-filter.pl_&; this makes a few arbitrary modifications just to
18175 show the possibilities. Exim does not check the result, except to test for a
18176 final newline when SMTP is in use. All messages transmitted over SMTP must end
18177 with a newline, so Exim supplies one if it is missing.
18179 .cindex "content scanning" "per user"
18180 A transport filter can be used to provide content-scanning on a per-user basis
18181 at delivery time if the only required effect of the scan is to modify the
18182 message. For example, a content scan could insert a new header line containing
18183 a spam score. This could be interpreted by a filter in the user's MUA. It is
18184 not possible to discard a message at this stage.
18186 .cindex "SMTP" "SIZE"
18187 A problem might arise if the filter increases the size of a message that is
18188 being sent down an SMTP connection. If the receiving SMTP server has indicated
18189 support for the SIZE parameter, Exim will have sent the size of the message
18190 at the start of the SMTP session. If what is actually sent is substantially
18191 more, the server might reject the message. This can be worked round by setting
18192 the &%size_addition%& option on the &(smtp)& transport, either to allow for
18193 additions to the message, or to disable the use of SIZE altogether.
18195 .cindex "&$pipe_addresses$&"
18196 The value of the &%transport_filter%& option is the command string for starting
18197 the filter, which is run directly from Exim, not under a shell. The string is
18198 parsed by Exim in the same way as a command string for the &(pipe)& transport:
18199 Exim breaks it up into arguments and then expands each argument separately (see
18200 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
18201 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
18202 of arguments, one for each address that applies to this delivery. (This isn't
18203 an ideal name for this feature here, but as it was already implemented for the
18204 &(pipe)& transport, it seemed sensible not to change it.)
18207 .cindex "&$host_address$&"
18208 The expansion variables &$host$& and &$host_address$& are available when the
18209 transport is a remote one. They contain the name and IP address of the host to
18210 which the message is being sent. For example:
18212 transport_filter = /some/directory/transport-filter.pl \
18213 $host $host_address $sender_address $pipe_addresses
18217 Two problems arise if you want to use more complicated expansion items to
18218 generate transport filter commands, both of which due to the fact that the
18219 command is split up &'before'& expansion.
18221 If an expansion item contains white space, you must quote it, so that it is all
18222 part of the same command item. If the entire option setting is one such
18223 expansion item, you have to take care what kind of quoting you use. For
18226 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
18228 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
18229 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
18230 stripped by Exim when it read the option's value. When the value is used, if
18231 the single quotes were missing, the line would be split into two items,
18232 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
18233 Exim tried to expand the first one.
18235 Except for the special case of &$pipe_addresses$& that is mentioned above, an
18236 expansion cannot generate multiple arguments, or a command name followed by
18237 arguments. Consider this example:
18239 transport_filter = ${lookup{$host}lsearch{/some/file}\
18240 {$value}{/bin/cat}}
18242 The result of the lookup is interpreted as the name of the command, even
18243 if it contains white space. The simplest way round this is to use a shell:
18245 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/some/file}\
18246 {$value}{/bin/cat}}
18251 The filter process is run under the same uid and gid as the normal delivery.
18252 For remote deliveries this is the Exim uid/gid by default. The command should
18253 normally yield a zero return code. Transport filters are not supposed to fail.
18254 A non-zero code is taken to mean that the transport filter encountered some
18255 serious problem. Delivery of the message is deferred; the message remains on
18256 the queue and is tried again later. It is not possible to cause a message to be
18257 bounced from a transport filter.
18259 If a transport filter is set on an autoreply transport, the original message is
18260 passed through the filter as it is being copied into the newly generated
18261 message, which happens if the &%return_message%& option is set.
18264 .option transport_filter_timeout transports time 5m
18265 .cindex "transport filter" "timeout"
18266 When Exim is reading the output of a transport filter, it a applies a timeout
18267 that can be set by this option. Exceeding the timeout is normally treated as a
18268 temporary delivery failure. However, if a transport filter is used with a
18269 &(pipe)& transport, a timeout in the transport filter is treated in the same
18270 way as a timeout in the pipe command itself. By default, a timeout is a hard
18271 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
18272 becomes a temporary error.
18275 .option user transports string&!! "Exim user"
18276 .cindex "uid (user id)" "local delivery"
18277 .cindex "transport user" "specifying"
18278 This option specifies the user under whose uid the delivery process is to be
18279 run, overriding any uid that may have been set by the router. If the user is
18280 given as a name, the uid is looked up from the password data, and the
18281 associated group is taken as the value of the gid to be used if the &%group%&
18284 For deliveries that use local transports, a user and group are normally
18285 specified explicitly or implicitly (for example, as a result of
18286 &%check_local_user%&) by the router or transport.
18288 .cindex "hints database" "access by remote transport"
18289 For remote transports, you should leave this option unset unless you really are
18290 sure you know what you are doing. When a remote transport is running, it needs
18291 to be able to access Exim's hints databases, because each host may have its own
18293 .ecindex IIDgenoptra1
18294 .ecindex IIDgenoptra2
18295 .ecindex IIDgenoptra3
18302 . ////////////////////////////////////////////////////////////////////////////
18303 . ////////////////////////////////////////////////////////////////////////////
18305 .chapter "Address batching in local transports" "CHAPbatching" &&&
18307 .cindex "transport" "local; address batching in"
18308 The only remote transport (&(smtp)&) is normally configured to handle more than
18309 one address at a time, so that when several addresses are routed to the same
18310 remote host, just one copy of the message is sent. Local transports, however,
18311 normally handle one address at a time. That is, a separate instance of the
18312 transport is run for each address that is routed to the transport. A separate
18313 copy of the message is delivered each time.
18315 .cindex "batched local delivery"
18316 .cindex "&%batch_max%&"
18317 .cindex "&%batch_id%&"
18318 In special cases, it may be desirable to handle several addresses at once in a
18319 local transport, for example:
18322 In an &(appendfile)& transport, when storing messages in files for later
18323 delivery by some other means, a single copy of the message with multiple
18324 recipients saves space.
18326 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
18327 a single copy saves time, and is the normal way LMTP is expected to work.
18329 In a &(pipe)& transport, when passing the message
18330 to a scanner program or
18331 to some other delivery mechanism such as UUCP, multiple recipients may be
18335 The three local transports (&(appendfile)&, &(lmtp)&, and &(pipe)&) all have
18336 the same options for controlling multiple (&"batched"&) deliveries, namely
18337 &%batch_max%& and &%batch_id%&. To save repeating the information for each
18338 transport, these options are described here.
18340 The &%batch_max%& option specifies the maximum number of addresses that can be
18341 delivered together in a single run of the transport. Its default value is one.
18342 When more than one address is routed to a transport that has a &%batch_max%&
18343 value greater than one, the addresses are delivered in a batch (that is, in a
18344 single run of the transport), subject to certain conditions:
18347 .cindex "&$local_part$&"
18348 If any of the transport's options contain a reference to &$local_part$&, no
18349 batching is possible.
18351 .cindex "&$domain$&"
18352 If any of the transport's options contain a reference to &$domain$&, only
18353 addresses with the same domain are batched.
18355 .cindex "customizing" "batching condition"
18356 If &%batch_id%& is set, it is expanded for each address, and only those
18357 addresses with the same expanded value are batched. This allows you to specify
18358 customized batching conditions.
18359 Failure of the expansion for any reason, including forced failure, disables
18360 batching, but it does not stop the delivery from taking place.
18362 Batched addresses must also have the same errors address (where to send
18363 delivery errors), the same header additions and removals, the same user and
18364 group for the transport, and if a host list is present, the first host must
18368 .cindex "&'Envelope-to:'& header line"
18369 If the generic &%envelope_to_add%& option is set for the transport, the
18370 &'Envelope-to:'& header that is added to the message contains all the addresses
18371 that are batched together.
18373 The &(appendfile)& and &(pipe)& transports have an option called &%use_bsmtp%&,
18374 which causes them to deliver the message in &"batched SMTP"& format, with the
18375 envelope represented as SMTP commands. The &%check_string%& and
18376 &%escape_string%& options are forced to the values
18379 escape_string = ".."
18381 when batched SMTP is in use. A full description of the batch SMTP mechanism is
18382 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
18383 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
18385 .cindex "&(pipe)& transport" "with multiple addresses"
18386 .cindex "&$pipe_addresses$&"
18387 If you are not using BSMTP, but are using a &(pipe)& transport, you can include
18388 &$pipe_addresses$& as part of the command. This is not a true variable; it is
18389 a bit of magic that causes each of the recipient addresses to be inserted into
18390 the command as a separate argument. This provides a way of accessing all the
18391 addresses that are being delivered in the batch.
18393 If you are using a batching &(appendfile)& transport without &%use_bsmtp%&, the
18394 only way to preserve the recipient addresses is to set the &%envelope_to_add%&
18395 option. This causes an &'Envelope-to:'& header line to be added to the message,
18396 containing all the recipients.
18400 . ////////////////////////////////////////////////////////////////////////////
18401 . ////////////////////////////////////////////////////////////////////////////
18403 .chapter "The appendfile transport" "CHAPappendfile"
18404 .scindex IIDapptra1 "&(appendfile)& transport"
18405 .scindex IIDapptra2 "transports" "&(appendfile)&"
18406 .cindex "directory creation"
18407 .cindex "creating directories"
18408 The &(appendfile)& transport delivers a message by appending it to an existing
18409 file, or by creating an entirely new file in a specified directory. Single
18410 files to which messages are appended can be in the traditional Unix mailbox
18411 format, or optionally in the MBX format supported by the Pine MUA and
18412 University of Washington IMAP daemon, &'inter alia'&. When each message is
18413 being delivered as a separate file, &"maildir"& format can optionally be used
18414 to give added protection against failures that happen part-way through the
18415 delivery. A third form of separate-file delivery known as &"mailstore"& is also
18416 supported. For all file formats, Exim attempts to create as many levels of
18417 directory as necessary, provided that &%create_directory%& is set.
18419 The code for the optional formats is not included in the Exim binary by
18420 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
18421 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
18424 .cindex "quota" "system"
18425 Exim recognises system quota errors, and generates an appropriate message. Exim
18426 also supports its own quota control within the transport, for use when the
18427 system facility is unavailable or cannot be used for some reason.
18429 If there is an error while appending to a file (for example, quota exceeded or
18430 partition filled), Exim attempts to reset the file's length and last
18431 modification time back to what they were before. If there is an error while
18432 creating an entirely new file, the new file is removed.
18434 Before appending to a file, a number of security checks are made, and the
18435 file is locked. A detailed description is given below, after the list of
18438 The &(appendfile)& transport is most commonly used for local deliveries to
18439 users' mailboxes. However, it can also be used as a pseudo-remote transport for
18440 putting messages into files for remote delivery by some means other than Exim.
18441 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
18446 .section "The file and directory options" "SECTfildiropt"
18447 The &%file%& option specifies a single file, to which the message is appended;
18448 the &%directory%& option specifies a directory, in which a new file containing
18449 the message is created. Only one of these two options can be set, and for
18450 normal deliveries to mailboxes, one of them &'must'& be set.
18452 .cindex "&$address_file$&"
18453 .cindex "&$local_part$&"
18454 However, &(appendfile)& is also used for delivering messages to files or
18455 directories whose names (or parts of names) are obtained from alias,
18456 forwarding, or filtering operations (for example, a &%save%& command in a
18457 user's Exim filter). When such a transport is running, &$local_part$& contains
18458 the local part that was aliased or forwarded, and &$address_file$& contains the
18459 name (or partial name) of the file or directory generated by the redirection
18460 operation. There are two cases:
18463 If neither &%file%& nor &%directory%& is set, the redirection operation
18464 must specify an absolute path (one that begins with &`/`&). This is the most
18465 common case when users with local accounts use filtering to sort mail into
18466 different folders. See for example, the &(address_file)& transport in the
18467 default configuration. If the path ends with a slash, it is assumed to be the
18468 name of a directory. A delivery to a directory can also be forced by setting
18469 &%maildir_format%& or &%mailstore_format%&.
18471 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
18472 used to determine the file or directory name for the delivery. Normally, the
18473 contents of &$address_file$& are used in some way in the string expansion.
18477 .cindex "Sieve filter" "configuring &(appendfile)&"
18478 .cindex "Sieve filter" "relative mailbox path handling"
18479 As an example of the second case, consider an environment where users do not
18480 have home directories. They may be permitted to use Exim filter commands of the
18485 or Sieve filter commands of the form:
18487 require "fileinto";
18488 fileinto "folder23";
18490 In this situation, the expansion of &%file%& or &%directory%& in the transport
18491 must transform the relative path into an appropriate absolute file name. In the
18492 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
18493 is used as a result of a &"keep"& action in the filter. This example shows one
18494 way of handling this requirement:
18496 file = ${if eq{$address_file}{inbox} \
18497 {/var/mail/$local_part} \
18498 {${if eq{${substr_0_1:$address_file}}{/} \
18500 {$home/mail/$address_file} \
18504 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
18505 location, absolute paths are used without change, and other folders are in the
18506 &_mail_& directory within the home directory.
18508 &*Note 1*&: While processing an Exim filter, a relative path such as
18509 &_folder23_& is turned into an absolute path if a home directory is known to
18510 the router. In particular, this is the case if &%check_local_user%& is set. If
18511 you want to prevent this happening at routing time, you can set
18512 &%router_home_directory%& empty. This forces the router to pass the relative
18513 path to the transport.
18515 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
18516 the &%file%& or &%directory%& option is still used if it is set.
18521 .section "Private options for appendfile"
18522 .cindex "options" "&(appendfile)& transport"
18526 .option allow_fifo appendfile boolean false
18527 .cindex "fifo (named pipe)"
18528 .cindex "named pipe (fifo)"
18529 .cindex "pipe" "named (fifo)"
18530 Setting this option permits delivery to named pipes (FIFOs) as well as to
18531 regular files. If no process is reading the named pipe at delivery time, the
18532 delivery is deferred.
18535 .option allow_symlink appendfile boolean false
18536 .cindex "symbolic link" "to mailbox"
18537 .cindex "mailbox" "symbolic link"
18538 By default, &(appendfile)& will not deliver if the path name for the file is
18539 that of a symbolic link. Setting this option relaxes that constraint, but there
18540 are security issues involved in the use of symbolic links. Be sure you know
18541 what you are doing if you set this. Details of exactly what this option affects
18542 are included in the discussion which follows this list of options.
18545 .option batch_id appendfile string&!! unset
18546 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
18547 However, batching is automatically disabled for &(appendfile)& deliveries that
18548 happen as a result of forwarding or aliasing or other redirection directly to a
18552 .option batch_max appendfile integer 1
18553 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
18556 .option check_group appendfile boolean false
18557 When this option is set, the group owner of the file defined by the &%file%&
18558 option is checked to see that it is the same as the group under which the
18559 delivery process is running. The default setting is false because the default
18560 file mode is 0600, which means that the group is irrelevant.
18563 .option check_owner appendfile boolean true
18564 When this option is set, the owner of the file defined by the &%file%& option
18565 is checked to ensure that it is the same as the user under which the delivery
18566 process is running.
18569 .option check_string appendfile string "see below"
18570 .cindex "&""From""& line"
18571 As &(appendfile)& writes the message, the start of each line is tested for
18572 matching &%check_string%&, and if it does, the initial matching characters are
18573 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
18574 a literal string, not a regular expression, and the case of any letters it
18575 contains is significant.
18577 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
18578 are forced to &"."& and &".."& respectively, and any settings in the
18579 configuration are ignored. Otherwise, they default to &"From&~"& and
18580 &">From&~"& when the &%file%& option is set, and unset when any of the
18581 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
18583 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
18584 suitable for traditional &"BSD"& mailboxes, where a line beginning with
18585 &"From&~"& indicates the start of a new message. All four options need changing
18586 if another format is used. For example, to deliver to mailboxes in MMDF format:
18587 .cindex "MMDF format mailbox"
18588 .cindex "mailbox" "MMDF format"
18590 check_string = "\1\1\1\1\n"
18591 escape_string = "\1\1\1\1 \n"
18592 message_prefix = "\1\1\1\1\n"
18593 message_suffix = "\1\1\1\1\n"
18595 .option create_directory appendfile boolean true
18596 .cindex "directory creation"
18597 When this option is true, Exim attempts to create any missing superior
18598 directories for the file that it is about to write. A created directory's mode
18599 is given by the &%directory_mode%& option.
18601 The group ownership of a newly created directory is highly dependent on the
18602 operating system (and possibly the file system) that is being used. For
18603 example, in Solaris, if the parent directory has the setgid bit set, its group
18604 is propagated to the child; if not, the currently set group is used. However,
18605 in FreeBSD, the parent's group is always used.
18609 .option create_file appendfile string anywhere
18610 This option constrains the location of files and directories that are created
18611 by this transport. It applies to files defined by the &%file%& option and
18612 directories defined by the &%directory%& option. In the case of maildir
18613 delivery, it applies to the top level directory, not the maildir directories
18616 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
18617 &"belowhome"&. In the second and third cases, a home directory must have been
18618 set for the transport. This option is not useful when an explicit file name is
18619 given for normal mailbox deliveries. It is intended for the case when file
18620 names are generated from users' &_.forward_& files. These are usually handled
18621 by an &(appendfile)& transport called &%address_file%&. See also
18622 &%file_must_exist%&.
18625 .option directory appendfile string&!! unset
18626 This option is mutually exclusive with the &%file%& option, but one of &%file%&
18627 or &%directory%& must be set, unless the delivery is the direct result of a
18628 redirection (see section &<<SECTfildiropt>>&).
18630 When &%directory%& is set, the string is expanded, and the message is delivered
18631 into a new file or files in or below the given directory, instead of being
18632 appended to a single mailbox file. A number of different formats are provided
18633 (see &%maildir_format%& and &%mailstore_format%&), and see section
18634 &<<SECTopdir>>& for further details of this form of delivery.
18637 .option directory_file appendfile string&!! &`q${base62:$tod_epoch}-$inode`&
18639 .cindex "&$inode$&"
18640 When &%directory%& is set, but neither &%maildir_format%& nor
18641 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
18642 whose name is obtained by expanding this string. The default value generates a
18643 unique name from the current time, in base 62 form, and the inode of the file.
18644 The variable &$inode$& is available only when expanding this option.
18647 .option directory_mode appendfile "octal integer" 0700
18648 If &(appendfile)& creates any directories as a result of the
18649 &%create_directory%& option, their mode is specified by this option.
18652 .option escape_string appendfile string "see description"
18653 See &%check_string%& above.
18656 .option file appendfile string&!! unset
18657 This option is mutually exclusive with the &%directory%& option, but one of
18658 &%file%& or &%directory%& must be set, unless the delivery is the direct result
18659 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
18660 specifies a single file, to which the message is appended. One or more of
18661 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
18664 .cindex "NFS" "lock file"
18665 .cindex "locking files"
18666 .cindex "lock files"
18667 If you are using more than one host to deliver over NFS into the same
18668 mailboxes, you should always use lock files.
18670 The string value is expanded for each delivery, and must yield an absolute
18671 path. The most common settings of this option are variations on one of these
18674 file = /var/spool/mail/$local_part
18675 file = /home/$local_part/inbox
18678 .cindex "&""sticky""& bit"
18679 In the first example, all deliveries are done into the same directory. If Exim
18680 is configured to use lock files (see &%use_lockfile%& below) it must be able to
18681 create a file in the directory, so the &"sticky"& bit must be turned on for
18682 deliveries to be possible, or alternatively the &%group%& option can be used to
18683 run the delivery under a group id which has write access to the directory.
18687 .option file_format appendfile string unset
18688 .cindex "file" "mailbox; checking existing format"
18689 This option requests the transport to check the format of an existing file
18690 before adding to it. The check consists of matching a specific string at the
18691 start of the file. The value of the option consists of an even number of
18692 colon-separated strings. The first of each pair is the test string, and the
18693 second is the name of a transport. If the transport associated with a matched
18694 string is not the current transport, control is passed over to the other
18695 transport. For example, suppose the standard &(local_delivery)& transport has
18698 file_format = "From : local_delivery :\
18699 \1\1\1\1\n : local_mmdf_delivery"
18701 Mailboxes that begin with &"From"& are still handled by this transport, but if
18702 a mailbox begins with four binary ones followed by a newline, control is passed
18703 to a transport called &%local_mmdf_delivery%&, which presumably is configured
18704 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
18705 is assumed to match the current transport. If the start of a mailbox doesn't
18706 match any string, or if the transport named for a given string is not defined,
18707 delivery is deferred.
18710 .option file_must_exist appendfile boolean false
18711 If this option is true, the file specified by the &%file%& option must exist,
18712 and an error occurs if it does not. Otherwise, it is created if it does not
18716 .option lock_fcntl_timeout appendfile time 0s
18717 .cindex "timeout" "mailbox locking"
18718 .cindex "mailbox locking" "blocking and non-blocking"
18719 .cindex "locking files"
18720 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
18721 when locking an open mailbox file. If the call fails, the delivery process
18722 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
18723 Non-blocking calls are used so that the file is not kept open during the wait
18724 for the lock; the reason for this is to make it as safe as possible for
18725 deliveries over NFS in the case when processes might be accessing an NFS
18726 mailbox without using a lock file. This should not be done, but
18727 misunderstandings and hence misconfigurations are not unknown.
18729 On a busy system, however, the performance of a non-blocking lock approach is
18730 not as good as using a blocking lock with a timeout. In this case, the waiting
18731 is done inside the system call, and Exim's delivery process acquires the lock
18732 and can proceed as soon as the previous lock holder releases it.
18734 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
18735 timeout, are used. There may still be some retrying: the maximum number of
18738 (lock_retries * lock_interval) / lock_fcntl_timeout
18740 rounded up to the next whole number. In other words, the total time during
18741 which &(appendfile)& is trying to get a lock is roughly the same, unless
18742 &%lock_fcntl_timeout%& is set very large.
18744 You should consider setting this option if you are getting a lot of delayed
18745 local deliveries because of errors of the form
18747 failed to lock mailbox /some/file (fcntl)
18750 .option lock_flock_timeout appendfile time 0s
18751 This timeout applies to file locking when using &[flock()]& (see
18752 &%use_flock%&); the timeout operates in a similar manner to
18753 &%lock_fcntl_timeout%&.
18756 .option lock_interval appendfile time 3s
18757 This specifies the time to wait between attempts to lock the file. See below
18758 for details of locking.
18761 .option lock_retries appendfile integer 10
18762 This specifies the maximum number of attempts to lock the file. A value of zero
18763 is treated as 1. See below for details of locking.
18766 .option lockfile_mode appendfile "octal integer" 0600
18767 This specifies the mode of the created lock file, when a lock file is being
18768 used (see &%use_lockfile%&).
18771 .option lockfile_timeout appendfile time 30m
18772 .cindex "timeout" "mailbox locking"
18773 When a lock file is being used (see &%use_lockfile%&), if a lock file already
18774 exists and is older than this value, it is assumed to have been left behind by
18775 accident, and Exim attempts to remove it.
18778 .option mailbox_filecount appendfile string&!! unset
18779 .cindex "mailbox" "specifying size of"
18780 .cindex "size" "of mailbox"
18781 If this option is set, it is expanded, and the result is taken as the current
18782 number of files in the mailbox. It must be a decimal number, optionally
18783 followed by K or M. This provides a way of obtaining this information from an
18784 external source that maintains the data.
18787 .option mailbox_size appendfile string&!! unset
18788 .cindex "mailbox" "specifying size of"
18789 .cindex "size" "of mailbox"
18790 If this option is set, it is expanded, and the result is taken as the current
18791 size the mailbox. It must be a decimal number, optionally followed by K or M.
18792 This provides a way of obtaining this information from an external source that
18793 maintains the data. This is likely to be helpful for maildir deliveries where
18794 it is computationally expensive to compute the size of a mailbox.
18798 .option maildir_format appendfile boolean false
18799 .cindex "maildir format" "specifying"
18800 If this option is set with the &%directory%& option, the delivery is into a new
18801 file, in the &"maildir"& format that is used by other mail software. When the
18802 transport is activated directly from a &(redirect)& router (for example, the
18803 &(address_file)& transport in the default configuration), setting
18804 &%maildir_format%& causes the path received from the router to be treated as a
18805 directory, whether or not it ends with &`/`&. This option is available only if
18806 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
18807 &<<SECTmaildirdelivery>>& below for further details.
18810 .option maildir_quota_directory_regex appendfile string "See below"
18811 .cindex "maildir format" "quota; directories included in"
18812 .cindex "quota" "maildir; directories included in"
18813 This option is relevant only when &%maildir_use_size_file%& is set. It defines
18814 a regular expression for specifying directories that should be included in the
18815 quota calculation. The default value is
18817 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
18819 which includes the &_cur_& and &_new_& directories, and any maildir++ folders
18820 (directories whose names begin with a dot). If you want to exclude the
18822 folder from the count (as some sites do), you need to change this setting to
18824 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
18826 This uses a negative lookahead in the regular expression to exclude the
18827 directory whose name is &_.Trash_&.
18830 .option maildir_retries appendfile integer 10
18831 This option specifies the number of times to retry when writing a file in
18832 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
18835 .option maildir_tag appendfile string&!! unset
18836 This option applies only to deliveries in maildir format, and is described in
18837 section &<<SECTmaildirdelivery>>& below.
18840 .option maildir_use_size_file appendfile boolean false
18841 .cindex "maildir format" "&_maildirsize_& file"
18842 Setting this option true enables support for &_maildirsize_& files. Exim
18843 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
18844 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
18845 value is zero. See section &<<SECTmaildirdelivery>>& below for further details.
18848 .option mailstore_format appendfile boolean false
18849 .cindex "mailstore format" "specifying"
18850 If this option is set with the &%directory%& option, the delivery is into two
18851 new files in &"mailstore"& format. The option is available only if
18852 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
18853 below for further details.
18856 .option mailstore_prefix appendfile string&!! unset
18857 This option applies only to deliveries in mailstore format, and is described in
18858 section &<<SECTopdir>>& below.
18861 .option mailstore_suffix appendfile string&!! unset
18862 This option applies only to deliveries in mailstore format, and is described in
18863 section &<<SECTopdir>>& below.
18866 .option mbx_format appendfile boolean false
18867 .cindex "locking files"
18868 .cindex "file" "locking"
18869 .cindex "file" "MBX format"
18870 .cindex "MBX format" "specifying"
18871 This option is available only if Exim has been compiled with SUPPORT_MBX
18872 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
18873 the message is appended to the mailbox file in MBX format instead of
18874 traditional Unix format. This format is supported by Pine4 and its associated
18875 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
18877 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
18878 automatically changed by the use of &%mbx_format%&. They should normally be set
18879 empty when using MBX format, so this option almost always appears in this
18886 If none of the locking options are mentioned in the configuration,
18887 &%use_mbx_lock%& is assumed and the other locking options default to false. It
18888 is possible to specify the other kinds of locking with &%mbx_format%&, but
18889 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
18890 interworks with &'c-client'&, providing for shared access to the mailbox. It
18891 should not be used if any program that does not use this form of locking is
18892 going to access the mailbox, nor should it be used if the mailbox file is NFS
18893 mounted, because it works only when the mailbox is accessed from a single host.
18895 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
18896 the standard version of &'c-client'&, because as long as it has a mailbox open
18897 (this means for the whole of a Pine or IMAP session), Exim will not be able to
18898 append messages to it.
18901 .option message_prefix appendfile string&!! "see below"
18902 .cindex "&""From""& line"
18903 The string specified here is expanded and output at the start of every message.
18904 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
18905 in which case it is:
18907 message_prefix = "From ${if def:return_path{$return_path}\
18908 {MAILER-DAEMON}} $tod_bsdinbox\n"
18912 .option message_suffix appendfile string&!! "see below"
18913 The string specified here is expanded and output at the end of every message.
18914 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
18915 in which case it is a single newline character. The suffix can be suppressed by
18921 .option mode appendfile "octal integer" 0600
18922 If the output file is created, it is given this mode. If it already exists and
18923 has wider permissions, they are reduced to this mode. If it has narrower
18924 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
18925 if the delivery is the result of a &%save%& command in a filter file specifing
18926 a particular mode, the mode of the output file is always forced to take that
18927 value, and this option is ignored.
18930 .option mode_fail_narrower appendfile boolean true
18931 This option applies in the case when an existing mailbox file has a narrower
18932 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
18933 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
18934 continues with the delivery attempt, using the existing mode of the file.
18937 .option notify_comsat appendfile boolean false
18938 If this option is true, the &'comsat'& daemon is notified after every
18939 successful delivery to a user mailbox. This is the daemon that notifies logged
18940 on users about incoming mail.
18943 .option quota appendfile string&!! unset
18944 .cindex "quota" "imposed by Exim"
18945 This option imposes a limit on the size of the file to which Exim is appending,
18946 or to the total space used in the directory tree when the &%directory%& option
18947 is set. In the latter case, computation of the space used is expensive, because
18948 all the files in the directory (and any sub-directories) have to be
18949 individually inspected and their sizes summed. (See &%quota_size_regex%& and
18950 &%maildir_use_size_file%& for ways to avoid this in environments where users
18951 have no shell access to their mailboxes).
18953 As there is no interlock against two simultaneous deliveries into a
18954 multi-file mailbox, it is possible for the quota to be overrun in this case.
18955 For single-file mailboxes, of course, an interlock is a necessity.
18957 A file's size is taken as its &'used'& value. Because of blocking effects, this
18958 may be a lot less than the actual amount of disk space allocated to the file.
18959 If the sizes of a number of files are being added up, the rounding effect can
18960 become quite noticeable, especially on systems that have large block sizes.
18961 Nevertheless, it seems best to stick to the &'used'& figure, because this is
18962 the obvious value which users understand most easily.
18964 The value of the option is expanded, and must then be a numerical value
18965 (decimal point allowed), optionally followed by one of the letters K, M, or G,
18966 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
18967 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
18970 &*Note*&: A value of zero is interpreted as &"no quota"&.
18972 The expansion happens while Exim is running as root, before it changes uid for
18973 the delivery. This means that files that are inaccessible to the end user can
18974 be used to hold quota values that are looked up in the expansion. When delivery
18975 fails because this quota is exceeded, the handling of the error is as for
18976 system quota failures.
18978 By default, Exim's quota checking mimics system quotas, and restricts the
18979 mailbox to the specified maximum size, though the value is not accurate to the
18980 last byte, owing to separator lines and additional headers that may get added
18981 during message delivery. When a mailbox is nearly full, large messages may get
18982 refused even though small ones are accepted, because the size of the current
18983 message is added to the quota when the check is made. This behaviour can be
18984 changed by setting &%quota_is_inclusive%& false. When this is done, the check
18985 for exceeding the quota does not include the current message. Thus, deliveries
18986 continue until the quota has been exceeded; thereafter, no further messages are
18987 delivered. See also &%quota_warn_threshold%&.
18990 .option quota_directory appendfile string&!! unset
18991 This option defines the directory to check for quota purposes when delivering
18992 into individual files. The default is the delivery directory, or, if a file
18993 called &_maildirfolder_& exists in a maildir directory, the parent of the
18994 delivery directory.
18997 .option quota_filecount appendfile string&!! 0
18999 This option applies when the &%directory%& option is set. It limits the total
19000 number of files in the directory (compare the inode limit in system quotas). It
19001 can only be used if &%quota%& is also set. The value is expanded; an expansion
19002 failure causes delivery to be deferred. A value of zero is interpreted as
19007 .option quota_is_inclusive appendfile boolean true
19008 See &%quota%& above.
19011 .option quota_size_regex appendfile string unset
19012 This option applies when one of the delivery modes that writes a separate file
19013 for each message is being used. When Exim wants to find the size of one of
19014 these files in order to test the quota, it first checks &%quota_size_regex%&.
19015 If this is set to a regular expression that matches the file name, and it
19016 captures one string, that string is interpreted as a representation of the
19017 file's size. The value of &%quota_size_regex%& is not expanded.
19019 This feature is useful only when users have no shell access to their mailboxes
19020 &-- otherwise they could defeat the quota simply by renaming the files. This
19021 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
19022 the file length to the file name. For example:
19024 maildir_tag = ,S=$message_size
19025 quota_size_regex = ,S=(\d+)
19027 An alternative to &$message_size$& is &$message_linecount$&, which contains the
19028 number of lines in the message.
19030 The regular expression should not assume that the length is at the end of the
19031 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
19032 sometimes add other information onto the ends of message file names.
19036 .option quota_warn_message appendfile string&!! "see below"
19037 See below for the use of this option. If it is not set when
19038 &%quota_warn_threshold%& is set, it defaults to
19040 quota_warn_message = "\
19041 To: $local_part@$domain\n\
19042 Subject: Your mailbox\n\n\
19043 This message is automatically created \
19044 by mail delivery software.\n\n\
19045 The size of your mailbox has exceeded \
19046 a warning threshold that is\n\
19047 set by the system administrator.\n"
19051 .option quota_warn_threshold appendfile string&!! 0
19052 .cindex "quota" "warning threshold"
19053 .cindex "mailbox" "size warning"
19054 .cindex "size" "of mailbox"
19055 This option is expanded in the same way as &%quota%& (see above). If the
19056 resulting value is greater than zero, and delivery of the message causes the
19057 size of the file or total space in the directory tree to cross the given
19058 threshold, a warning message is sent. If &%quota%& is also set, the threshold
19059 may be specified as a percentage of it by following the value with a percent
19063 quota_warn_threshold = 75%
19065 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
19066 percent sign is ignored.
19069 The warning message itself is specified by the &%quota_warn_message%& option,
19070 and it must start with a &'To:'& header line containing the recipient(s) of the
19071 warning message. These do not necessarily have to include the recipient(s) of
19072 the original message. A &'Subject:'& line should also normally be supplied. You
19073 can include any other header lines that you want. If you do not include a
19074 &'From:'& line, the default is:
19076 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
19078 .oindex &%errors_reply_to%&
19079 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
19083 The &%quota%& option does not have to be set in order to use this option; they
19084 are independent of one another except when the threshold is specified as a
19088 .option use_bsmtp appendfile boolean false
19089 .cindex "envelope sender"
19090 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
19091 format, with the envelope sender and recipient(s) included as SMTP commands. If
19092 you want to include a leading HELO command with such messages, you can do
19093 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
19094 for details of batch SMTP.
19097 .option use_crlf appendfile boolean false
19098 .cindex "carriage return"
19100 This option causes lines to be terminated with the two-character CRLF sequence
19101 (carriage return, linefeed) instead of just a linefeed character. In the case
19102 of batched SMTP, the byte sequence written to the file is then an exact image
19103 of what would be sent down a real SMTP connection.
19105 The contents of the &%message_prefix%& and &%message_suffix%& options are
19106 written verbatim, so must contain their own carriage return characters if these
19107 are needed. In cases where these options have non-empty defaults, the values
19108 end with a single linefeed, so they must be changed to end with &`\r\n`& if
19109 &%use_crlf%& is set.
19112 .option use_fcntl_lock appendfile boolean "see below"
19113 This option controls the use of the &[fcntl()]& function to lock a file for
19114 exclusive use when a message is being appended. It is set by default unless
19115 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
19116 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
19117 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
19120 .option use_flock_lock appendfile boolean false
19121 This option is provided to support the use of &[flock()]& for file locking, for
19122 the few situations where it is needed. Most modern operating systems support
19123 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
19124 each other. Exim uses &[fcntl()]& locking by default.
19126 This option is required only if you are using an operating system where
19127 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
19128 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
19129 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
19131 .cindex "Solaris" "&[flock()]& support"
19132 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
19133 have it (and some, I think, provide a not quite right version built on top of
19134 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
19135 the ability to use it, and any attempt to do so will cause a configuration
19138 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
19139 is just being mapped onto &[fcntl()]& by the OS).
19142 .option use_lockfile appendfile boolean "see below"
19143 If this option is turned off, Exim does not attempt to create a lock file when
19144 appending to a mailbox file. In this situation, the only locking is by
19145 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
19146 sure that every MUA that is ever going to look at your users' mailboxes uses
19147 &[fcntl()]& rather than a lock file, and even then only when you are not
19148 delivering over NFS from more than one host.
19150 .cindex "NFS" "lock file"
19151 In order to append to an NFS file safely from more than one host, it is
19152 necessary to take out a lock &'before'& opening the file, and the lock file
19153 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
19156 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
19157 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
19158 except when &%mbx_format%& is set.
19161 .option use_mbx_lock appendfile boolean "see below"
19162 This option is available only if Exim has been compiled with SUPPORT_MBX
19163 set in &_Local/Makefile_&. Setting the option specifies that special MBX
19164 locking rules be used. It is set by default if &%mbx_format%& is set and none
19165 of the locking options are mentioned in the configuration. The locking rules
19166 are the same as are used by the &'c-client'& library that underlies Pine and
19167 the IMAP4 and POP daemons that come with it (see the discussion below). The
19168 rules allow for shared access to the mailbox. However, this kind of locking
19169 does not work when the mailbox is NFS mounted.
19171 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
19172 &%use_flock_lock%& to control what kind of locking is used in implementing the
19173 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
19174 without &%use_fcntl_lock%& or &%use_flock_lock%&.
19179 .section "Operational details for appending" "SECTopappend"
19180 .cindex "appending to a file"
19181 .cindex "file" "appending"
19182 Before appending to a file, the following preparations are made:
19185 If the name of the file is &_/dev/null_&, no action is taken, and a success
19189 .cindex "directory creation"
19190 If any directories on the file's path are missing, Exim creates them if the
19191 &%create_directory%& option is set. A created directory's mode is given by the
19192 &%directory_mode%& option.
19195 If &%file_format%& is set, the format of an existing file is checked. If this
19196 indicates that a different transport should be used, control is passed to that
19200 .cindex "file" "locking"
19201 .cindex "locking files"
19202 .cindex "NFS" "lock file"
19203 If &%use_lockfile%& is set, a lock file is built in a way that will work
19204 reliably over NFS, as follows:
19207 Create a &"hitching post"& file whose name is that of the lock file with the
19208 current time, primary host name, and process id added, by opening for writing
19209 as a new file. If this fails with an access error, delivery is deferred.
19211 Close the hitching post file, and hard link it to the lock file name.
19213 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
19214 Unlink the hitching post name.
19216 Otherwise, use &[stat()]& to get information about the hitching post file, and
19217 then unlink hitching post name. If the number of links is exactly two, creation
19218 of the lock file succeeded but something (for example, an NFS server crash and
19219 restart) caused this fact not to be communicated to the &[link()]& call.
19221 If creation of the lock file failed, wait for &%lock_interval%& and try again,
19222 up to &%lock_retries%& times. However, since any program that writes to a
19223 mailbox should complete its task very quickly, it is reasonable to time out old
19224 lock files that are normally the result of user agent and system crashes. If an
19225 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
19226 it before trying again.
19230 A call is made to &[lstat()]& to discover whether the main file exists, and if
19231 so, what its characteristics are. If &[lstat()]& fails for any reason other
19232 than non-existence, delivery is deferred.
19235 .cindex "symbolic link" "to mailbox"
19236 .cindex "mailbox" "symbolic link"
19237 If the file does exist and is a symbolic link, delivery is deferred, unless the
19238 &%allow_symlink%& option is set, in which case the ownership of the link is
19239 checked, and then &[stat()]& is called to find out about the real file, which
19240 is then subjected to the checks below. The check on the top-level link
19241 ownership prevents one user creating a link for another's mailbox in a sticky
19242 directory, though allowing symbolic links in this case is definitely not a good
19243 idea. If there is a chain of symbolic links, the intermediate ones are not
19247 If the file already exists but is not a regular file, or if the file's owner
19248 and group (if the group is being checked &-- see &%check_group%& above) are
19249 different from the user and group under which the delivery is running,
19250 delivery is deferred.
19253 If the file's permissions are more generous than specified, they are reduced.
19254 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
19255 is set false, in which case the delivery is tried using the existing
19259 The file's inode number is saved, and the file is then opened for appending.
19260 If this fails because the file has vanished, &(appendfile)& behaves as if it
19261 hadn't existed (see below). For any other failures, delivery is deferred.
19264 If the file is opened successfully, check that the inode number hasn't
19265 changed, that it is still a regular file, and that the owner and permissions
19266 have not changed. If anything is wrong, defer delivery and freeze the message.
19269 If the file did not exist originally, defer delivery if the &%file_must_exist%&
19270 option is set. Otherwise, check that the file is being created in a permitted
19271 directory if the &%create_file%& option is set (deferring on failure), and then
19272 open for writing as a new file, with the O_EXCL and O_CREAT options,
19273 except when dealing with a symbolic link (the &%allow_symlink%& option must be
19274 set). In this case, which can happen if the link points to a non-existent file,
19275 the file is opened for writing using O_CREAT but not O_EXCL, because
19276 that prevents link following.
19279 .cindex "loop" "while file testing"
19280 If opening fails because the file exists, obey the tests given above for
19281 existing files. However, to avoid looping in a situation where the file is
19282 being continuously created and destroyed, the exists/not-exists loop is broken
19283 after 10 repetitions, and the message is then frozen.
19286 If opening fails with any other error, defer delivery.
19289 .cindex "file" "locking"
19290 .cindex "locking files"
19291 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
19292 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
19293 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
19294 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
19295 file, and an exclusive lock on the file whose name is
19297 /tmp/.<device-number>.<inode-number>
19299 using the device and inode numbers of the open mailbox file, in accordance with
19300 the MBX locking rules.
19302 If Exim fails to lock the file, there are two possible courses of action,
19303 depending on the value of the locking timeout. This is obtained from
19304 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
19306 If the timeout value is zero, the file is closed, Exim waits for
19307 &%lock_interval%&, and then goes back and re-opens the file as above and tries
19308 to lock it again. This happens up to &%lock_retries%& times, after which the
19309 delivery is deferred.
19311 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
19312 &[flock()]& are used (with the given timeout), so there has already been some
19313 waiting involved by the time locking fails. Nevertheless, Exim does not give up
19314 immediately. It retries up to
19316 (lock_retries * lock_interval) / <timeout>
19318 times (rounded up).
19321 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
19322 and/or &[flock()]& locks) and then deletes the lock file if one was created.
19325 .section "Operational details for delivery to a new file" "SECTopdir"
19326 .cindex "delivery" "to single file"
19327 .cindex "&""From""& line"
19328 When the &%directory%& option is set instead of &%file%&, each message is
19329 delivered into a newly-created file or set of files. When &(appendfile)& is
19330 activated directly from a &(redirect)& router, neither &%file%& nor
19331 &%directory%& is normally set, because the path for delivery is supplied by the
19332 router. (See for example, the &(address_file)& transport in the default
19333 configuration.) In this case, delivery is to a new file if either the path name
19334 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
19336 No locking is required while writing the message to a new file, so the various
19337 locking options of the transport are ignored. The &"From"& line that by default
19338 separates messages in a single file is not normally needed, nor is the escaping
19339 of message lines that start with &"From"&, and there is no need to ensure a
19340 newline at the end of each message. Consequently, the default values for
19341 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
19342 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
19344 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
19345 the files in the delivery directory by default. However, you can specify a
19346 different directory by setting &%quota_directory%&. Also, for maildir
19347 deliveries (see below) the &_maildirfolder_& convention is honoured.
19350 .cindex "maildir format"
19351 .cindex "mailstore format"
19352 There are three different ways in which delivery to individual files can be
19353 done, controlled by the settings of the &%maildir_format%& and
19354 &%mailstore_format%& options. Note that code to support maildir or mailstore
19355 formats is not included in the binary unless SUPPORT_MAILDIR or
19356 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
19358 .cindex "directory creation"
19359 In all three cases an attempt is made to create the directory and any necessary
19360 sub-directories if they do not exist, provided that the &%create_directory%&
19361 option is set (the default). The location of a created directory can be
19362 constrained by setting &%create_file%&. A created directory's mode is given by
19363 the &%directory_mode%& option. If creation fails, or if the
19364 &%create_directory%& option is not set when creation is required, delivery is
19369 .section "Maildir delivery" "SECTmaildirdelivery"
19370 .cindex "maildir format" "description of"
19371 If the &%maildir_format%& option is true, Exim delivers each message by writing
19372 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
19373 given directory. If the delivery is successful, the file is renamed into the
19374 &_new_& subdirectory.
19376 In the file name, <&'stime'&> is the current time of day in seconds, and
19377 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
19378 Exim checks that the time-of-day clock has moved on by at least one microsecond
19379 before terminating the delivery process. This guarantees uniqueness for the
19380 file name. However, as a precaution, Exim calls &[stat()]& for the file before
19381 opening it. If any response other than ENOENT (does not exist) is given,
19382 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
19384 .cindex "quota" "in maildir delivery"
19385 .cindex "maildir++"
19386 If Exim is required to check a &%quota%& setting before a maildir delivery, and
19387 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
19388 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
19389 Exim assumes the directory is a maildir++ folder directory, which is one level
19390 down from the user's top level mailbox directory. This causes it to start at
19391 the parent directory instead of the current directory when calculating the
19392 amount of space used.
19394 One problem with delivering into a multi-file mailbox is that it is
19395 computationally expensive to compute the size of the mailbox for quota
19396 checking. Various approaches have been taken to reduce the amount of work
19397 needed. The next two sections describe two of them. A third alternative is to
19398 use some external process for maintaining the size data, and use the expansion
19399 of the &%mailbox_size%& option as a way of importing it into Exim.
19404 .section "Using tags to record message sizes"
19405 If &%maildir_tag%& is set, the string is expanded for each delivery.
19406 When the maildir file is renamed into the &_new_& sub-directory, the
19407 tag is added to its name. However, if adding the tag takes the length of the
19408 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
19409 the tag is dropped and the maildir file is created with no tag.
19411 .cindex "&$message_size$&"
19412 Tags can be used to encode the size of files in their names; see
19413 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
19414 happens after the message has been written. The value of the &$message_size$&
19415 variable is set to the number of bytes actually written. If the expansion is
19416 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
19417 be deferred. The expanded tag may contain any printing characters except &"/"&.
19418 Non-printing characters in the string are ignored; if the resulting string is
19419 empty, it is ignored. If it starts with an alphanumeric character, a leading
19424 .section "Using a maildirsize file"
19425 .cindex "quota" "in maildir delivery"
19426 .cindex "maildir format" "&_maildirsize_& file"
19427 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
19428 storing quota and message size information in a file called &_maildirsize_&
19429 within the maildir directory. If this file does not exist, Exim creates it,
19430 setting the quota from the &%quota%& option of the transport. If the maildir
19431 directory itself does not exist, it is created before any attempt to write a
19432 &_maildirsize_& file.
19434 The &_maildirsize_& file is used to hold information about the sizes of
19435 messages in the maildir, thus speeding up quota calculations. The quota value
19436 in the file is just a cache; if the quota is changed in the transport, the new
19437 value overrides the cached value when the next message is delivered. The cache
19438 is maintained for the benefit of other programs that access the maildir and
19439 need to know the quota.
19441 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
19442 file is maintained (with a zero quota setting), but no quota is imposed.
19444 A regular expression is available for controlling which directories in the
19445 maildir participate in quota calculations. See the description of the
19446 &%maildir_quota_directory_regex%& option above for details.
19450 .section "Mailstore delivery"
19451 .cindex "mailstore format" "description of"
19452 If the &%mailstore_format%& option is true, each message is written as two
19453 files in the given directory. A unique base name is constructed from the
19454 message id and the current delivery process, and the files that are written use
19455 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
19456 contains the message's envelope, and the &_.msg_& file contains the message
19457 itself. The base name is placed in the variable &$mailstore_basename$&.
19459 During delivery, the envelope is first written to a file with the suffix
19460 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
19461 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
19462 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
19463 file before accessing either of them. An alternative approach is to wait for
19464 the absence of a &_.tmp_& file.
19466 The envelope file starts with any text defined by the &%mailstore_prefix%&
19467 option, expanded and terminated by a newline if there isn't one. Then follows
19468 the sender address on one line, then all the recipient addresses, one per line.
19469 There can be more than one recipient only if the &%batch_max%& option is set
19470 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
19471 appended to the file, followed by a newline if it does not end with one.
19473 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
19474 failure, it is ignored. Other expansion errors are treated as serious
19475 configuration errors, and delivery is deferred. The variable
19476 &$mailstore_basename$& is available for use during these expansions.
19479 .section "Non-special new file delivery"
19480 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
19481 file is created directly in the named directory. For example, when delivering
19482 messages into files in batched SMTP format for later delivery to some host (see
19483 section &<<SECTbatchSMTP>>&), a setting such as
19485 directory = /var/bsmtp/$host
19487 might be used. A message is written to a file with a temporary name, which is
19488 then renamed when the delivery is complete. The final name is obtained by
19489 expanding the contents of the &%directory_file%& option.
19490 .ecindex IIDapptra1
19491 .ecindex IIDapptra2
19498 . ////////////////////////////////////////////////////////////////////////////
19499 . ////////////////////////////////////////////////////////////////////////////
19501 .chapter "The autoreply transport"
19502 .scindex IIDauttra1 "transports" "&(autoreply)&"
19503 .scindex IIDauttra2 "&(autoreply)& transport"
19505 The &(autoreply)& transport is not a true transport in that it does not cause
19506 the message to be transmitted. Instead, it generates a new mail message as an
19507 automatic reply to the incoming message. &'References:'& and
19508 &'Auto-Submitted:'& header lines are included. These are constructed according
19509 to the rules in RFCs 2822 and 3834, respectively.
19512 If the router that passes the message to this transport does not have the
19513 &%unseen%& option set, the original message (for the current recipient) is not
19514 delivered anywhere. However, when the &%unseen%& option is set on the router
19515 that passes the message to this transport, routing of the address continues, so
19516 another router can set up a normal message delivery.
19519 The &(autoreply)& transport is usually run as the result of mail filtering, a
19520 &"vacation"& message being the standard example. However, it can also be run
19521 directly from a router like any other transport. To reduce the possibility of
19522 message cascades, messages created by the &(autoreply)& transport always have
19523 empty envelope sender addresses, like bounce messages.
19525 The parameters of the message to be sent can be specified in the configuration
19526 by options described below. However, these are used only when the address
19527 passed to the transport does not contain its own reply information. When the
19528 transport is run as a consequence of a
19530 or &%vacation%& command in a filter file, the parameters of the message are
19531 supplied by the filter, and passed with the address. The transport's options
19532 that define the message are then ignored (so they are not usually set in this
19533 case). The message is specified entirely by the filter or by the transport; it
19534 is never built from a mixture of options. However, the &%file_optional%&,
19535 &%mode%&, and &%return_message%& options apply in all cases.
19537 &(Autoreply)& is implemented as a local transport. When used as a result of a
19538 command in a user's filter file, &(autoreply)& normally runs under the uid and
19539 gid of the user, and with appropriate current and home directories (see chapter
19540 &<<CHAPenvironment>>&).
19542 There is a subtle difference between routing a message to a &(pipe)& transport
19543 that generates some text to be returned to the sender, and routing it to an
19544 &(autoreply)& transport. This difference is noticeable only if more than one
19545 address from the same message is so handled. In the case of a pipe, the
19546 separate outputs from the different addresses are gathered up and returned to
19547 the sender in a single message, whereas if &(autoreply)& is used, a separate
19548 message is generated for each address that is passed to it.
19550 Non-printing characters are not permitted in the header lines generated for the
19551 message that &(autoreply)& creates, with the exception of newlines that are
19552 immediately followed by white space. If any non-printing characters are found,
19553 the transport defers.
19554 Whether characters with the top bit set count as printing characters or not is
19555 controlled by the &%print_topbitchars%& global option.
19557 If any of the generic options for manipulating headers (for example,
19558 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
19559 of the original message that is included in the generated message when
19560 &%return_message%& is set. They do not apply to the generated message itself.
19562 .cindex "&$sender_address$&"
19563 If the &(autoreply)& transport receives return code 2 from Exim when it submits
19564 the message, indicating that there were no recipients, it does not treat this
19565 as an error. This means that autoreplies sent to &$sender_address$& when this
19566 is empty (because the incoming message is a bounce message) do not cause
19567 problems. They are just discarded.
19571 .section "Private options for autoreply"
19572 .cindex "options" "&(autoreply)& transport"
19574 .option bcc autoreply string&!! unset
19575 This specifies the addresses that are to receive &"blind carbon copies"& of the
19576 message when the message is specified by the transport.
19579 .option cc autoreply string&!! unset
19580 This specifies recipients of the message and the contents of the &'Cc:'& header
19581 when the message is specified by the transport.
19584 .option file autoreply string&!! unset
19585 The contents of the file are sent as the body of the message when the message
19586 is specified by the transport. If both &%file%& and &%text%& are set, the text
19587 string comes first.
19590 .option file_expand autoreply boolean false
19591 If this is set, the contents of the file named by the &%file%& option are
19592 subjected to string expansion as they are added to the message.
19595 .option file_optional autoreply boolean false
19596 If this option is true, no error is generated if the file named by the &%file%&
19597 option or passed with the address does not exist or cannot be read.
19600 .option from autoreply string&!! unset
19601 This specifies the contents of the &'From:'& header when the message is
19602 specified by the transport.
19605 .option headers autoreply string&!! unset
19606 This specifies additional RFC 2822 headers that are to be added to the message
19607 when the message is specified by the transport. Several can be given by using
19608 &"\n"& to separate them. There is no check on the format.
19611 .option log autoreply string&!! unset
19612 This option names a file in which a record of every message sent is logged when
19613 the message is specified by the transport.
19616 .option mode autoreply "octal integer" 0600
19617 If either the log file or the &"once"& file has to be created, this mode is
19621 .option never_mail autoreply "address list&!!" unset
19622 If any run of the transport creates a message with a recipient that matches any
19623 item in the list, that recipient is quietly discarded. If all recipients are
19624 discarded, no message is created.
19628 .option once autoreply string&!! unset
19629 This option names a file or DBM database in which a record of each &'To:'&
19630 recipient is kept when the message is specified by the transport. &*Note*&:
19631 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
19633 If &%once%& is unset, or is set to an empty string, the message is always sent.
19634 By default, if &%once%& is set to a non-empty file name, the message
19635 is not sent if a potential recipient is already listed in the database.
19636 However, if the &%once_repeat%& option specifies a time greater than zero, the
19637 message is sent if that much time has elapsed since a message was last sent to
19638 this recipient. A setting of zero time for &%once_repeat%& (the default)
19639 prevents a message from being sent a second time &-- in this case, zero means
19642 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
19643 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
19644 greater than zero, it changes the way Exim implements the &%once%& option.
19645 Instead of using a DBM file to record every recipient it sends to, it uses a
19646 regular file, whose size will never get larger than the given value.
19648 In the file, Exim keeps a linear list of recipient addresses and the times at
19649 which they were sent messages. If the file is full when a new address needs to
19650 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
19651 means that a given recipient may receive multiple messages, but at
19652 unpredictable intervals that depend on the rate of turnover of addresses in the
19653 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
19656 .option once_file_size autoreply integer 0
19657 See &%once%& above.
19660 .option once_repeat autoreply time&!! 0s
19661 See &%once%& above.
19662 After expansion, the value of this option must be a valid time value.
19665 .option reply_to autoreply string&!! unset
19666 This specifies the contents of the &'Reply-To:'& header when the message is
19667 specified by the transport.
19670 .option return_message autoreply boolean false
19671 If this is set, a copy of the original message is returned with the new
19672 message, subject to the maximum size set in the &%return_size_limit%& global
19673 configuration option.
19676 .option subject autoreply string&!! unset
19677 This specifies the contents of the &'Subject:'& header when the message is
19678 specified by the transport. It is tempting to quote the original subject in
19679 automatic responses. For example:
19681 subject = Re: $h_subject:
19683 There is a danger in doing this, however. It may allow a third party to
19684 subscribe your users to an opt-in mailing list, provided that the list accepts
19685 bounce messages as subscription confirmations. Well-managed lists require a
19686 non-bounce message to confirm a subscription, so the danger is relatively
19691 .option text autoreply string&!! unset
19692 This specifies a single string to be used as the body of the message when the
19693 message is specified by the transport. If both &%text%& and &%file%& are set,
19694 the text comes first.
19697 .option to autoreply string&!! unset
19698 This specifies recipients of the message and the contents of the &'To:'& header
19699 when the message is specified by the transport.
19700 .ecindex IIDauttra1
19701 .ecindex IIDauttra2
19706 . ////////////////////////////////////////////////////////////////////////////
19707 . ////////////////////////////////////////////////////////////////////////////
19709 .chapter "The lmtp transport" "CHAPLMTP"
19710 .cindex "transports" "&(lmtp)&"
19711 .cindex "&(lmtp)& transport"
19712 .cindex "LMTP" "over a pipe"
19713 .cindex "LMTP" "over a socket"
19714 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
19716 or by interacting with a Unix domain socket.
19717 This transport is something of a cross between the &(pipe)& and &(smtp)&
19718 transports. Exim also has support for using LMTP over TCP/IP; this is
19719 implemented as an option for the &(smtp)& transport. Because LMTP is expected
19720 to be of minority interest, the default build-time configure in &_src/EDITME_&
19721 has it commented out. You need to ensure that
19725 .cindex "options" "&(lmtp)& transport"
19726 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
19727 included in the Exim binary. The private options of the &(lmtp)& transport are
19730 .option batch_id lmtp string&!! unset
19731 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19734 .option batch_max lmtp integer 1
19735 This limits the number of addresses that can be handled in a single delivery.
19736 Most LMTP servers can handle several addresses at once, so it is normally a
19737 good idea to increase this value. See the description of local delivery
19738 batching in chapter &<<CHAPbatching>>&.
19741 .option command lmtp string&!! unset
19742 This option must be set if &%socket%& is not set. The string is a command which
19743 is run in a separate process. It is split up into a command name and list of
19744 arguments, each of which is separately expanded (so expansion cannot change the
19745 number of arguments). The command is run directly, not via a shell. The message
19746 is passed to the new process using the standard input and output to operate the
19749 .option ignore_quota lmtp boolean false
19750 .cindex "LMTP" "ignoring quota errors"
19751 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
19752 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
19753 in its response to the LHLO command.
19755 .option socket lmtp string&!! unset
19756 This option must be set if &%command%& is not set. The result of expansion must
19757 be the name of a Unix domain socket. The transport connects to the socket and
19758 delivers the message to it using the LMTP protocol.
19761 .option timeout lmtp time 5m
19762 The transport is aborted if the created process
19763 or Unix domain socket
19764 does not respond to LMTP commands or message input within this timeout.
19767 Here is an example of a typical LMTP transport:
19771 command = /some/local/lmtp/delivery/program
19775 This delivers up to 20 addresses at a time, in a mixture of domains if
19776 necessary, running as the user &'exim'&.
19780 . ////////////////////////////////////////////////////////////////////////////
19781 . ////////////////////////////////////////////////////////////////////////////
19783 .chapter "The pipe transport" "CHAPpipetransport"
19784 .scindex IIDpiptra1 "transports" "&(pipe)&"
19785 .scindex IIDpiptra2 "&(pipe)& transport"
19786 The &(pipe)& transport is used to deliver messages via a pipe to a command
19787 running in another process. One example is the use of &(pipe)& as a
19788 pseudo-remote transport for passing messages to some other delivery mechanism
19789 (such as UUCP). Another is the use by individual users to automatically process
19790 their incoming messages. The &(pipe)& transport can be used in one of the
19794 .cindex "&$local_part$&"
19795 A router routes one address to a transport in the normal way, and the
19796 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
19797 contains the local part of the address (as usual), and the command that is run
19798 is specified by the &%command%& option on the transport.
19800 .cindex "&$pipe_addresses$&"
19801 If the &%batch_max%& option is set greater than 1 (the default), the transport
19802 can be called upon to handle more than one address in a single run. In this
19803 case, &$local_part$& is not set (because it is not unique). However, the
19804 pseudo-variable &$pipe_addresses$& (described in section
19805 &<<SECThowcommandrun>>& below) contains all the addresses that are being
19808 .cindex "&$address_pipe$&"
19809 A router redirects an address directly to a pipe command (for example, from an
19810 alias or forward file). In this case, &$local_part$& contains the local part
19811 that was redirected, and &$address_pipe$& contains the text of the pipe
19812 command itself. The &%command%& option on the transport is ignored.
19816 The &(pipe)& transport is a non-interactive delivery method. Exim can also
19817 deliver messages over pipes using the LMTP interactive protocol. This is
19818 implemented by the &(lmtp)& transport.
19820 In the case when &(pipe)& is run as a consequence of an entry in a local user's
19821 &_.forward_& file, the command runs under the uid and gid of that user. In
19822 other cases, the uid and gid have to be specified explicitly, either on the
19823 transport or on the router that handles the address. Current and &"home"&
19824 directories are also controllable. See chapter &<<CHAPenvironment>>& for
19825 details of the local delivery environment.
19829 .section "Concurrent delivery"
19830 If two messages arrive at almost the same time, and both are routed to a pipe
19831 delivery, the two pipe transports may be run concurrently. You must ensure that
19832 any pipe commands you set up are robust against this happening. If the commands
19833 write to a file, the &%exim_lock%& utility might be of use.
19838 .section "Returned status and data"
19839 .cindex "&(pipe)& transport" "returned data"
19840 If the command exits with a non-zero return code, the delivery is deemed to
19841 have failed, unless either the &%ignore_status%& option is set (in which case
19842 the return code is treated as zero), or the return code is one of those listed
19843 in the &%temp_errors%& option, which are interpreted as meaning &"try again
19844 later"&. In this case, delivery is deferred. Details of a permanent failure are
19845 logged, but are not included in the bounce message, which merely contains
19846 &"local delivery failed"&.
19848 If the return code is greater than 128 and the command being run is a shell
19849 script, it normally means that the script was terminated by a signal whose
19850 value is the return code minus 128.
19852 If Exim is unable to run the command (that is, if &[execve()]& fails), the
19853 return code is set to 127. This is the value that a shell returns if it is
19854 asked to run a non-existent command. The wording for the log line suggests that
19855 a non-existent command may be the problem.
19857 The &%return_output%& option can affect the result of a pipe delivery. If it is
19858 set and the command produces any output on its standard output or standard
19859 error streams, the command is considered to have failed, even if it gave a zero
19860 return code or if &%ignore_status%& is set. The output from the command is
19861 included as part of the bounce message. The &%return_fail_output%& option is
19862 similar, except that output is returned only when the command exits with a
19863 failure return code, that is, a value other than zero or a code that matches
19868 .section "How the command is run" "SECThowcommandrun"
19869 .cindex "&(pipe)& transport" "path for command"
19870 The command line is (by default) broken down into a command name and arguments
19871 by the &(pipe)& transport itself. The &%allow_commands%& and
19872 &%restrict_to_path%& options can be used to restrict the commands that may be
19875 .cindex "quoting" "in pipe command"
19876 Unquoted arguments are delimited by white space. If an argument appears in
19877 double quotes, backslash is interpreted as an escape character in the usual
19878 way. If an argument appears in single quotes, no escaping is done.
19880 String expansion is applied to the command line except when it comes from a
19881 traditional &_.forward_& file (commands from a filter file are expanded). The
19882 expansion is applied to each argument in turn rather than to the whole line.
19883 For this reason, any string expansion item that contains white space must be
19884 quoted so as to be contained within a single argument. A setting such as
19886 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
19888 will not work, because the expansion item gets split between several
19889 arguments. You have to write
19891 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
19894 to ensure that it is all in one argument. The expansion is done in this way,
19895 argument by argument, so that the number of arguments cannot be changed as a
19896 result of expansion, and quotes or backslashes in inserted variables do not
19897 interact with external quoting. However, this leads to problems if you want to
19898 generate multiple arguments (or the command name plus arguments) from a single
19899 expansion. In this situation, the simplest solution is to use a shell. For
19902 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
19906 .cindex "transport" "filter"
19907 .cindex "filter" "transport filter"
19908 .cindex "&$pipe_addresses$&"
19909 Special handling takes place when an argument consists of precisely the text
19910 &`$pipe_addresses`&. This is not a general expansion variable; the only
19911 place this string is recognized is when it appears as an argument for a pipe or
19912 transport filter command. It causes each address that is being handled to be
19913 inserted in the argument list at that point &'as a separate argument'&. This
19914 avoids any problems with spaces or shell metacharacters, and is of use when a
19915 &(pipe)& transport is handling groups of addresses in a batch.
19917 After splitting up into arguments and expansion, the resulting command is run
19918 in a subprocess directly from the transport, &'not'& under a shell. The
19919 message that is being delivered is supplied on the standard input, and the
19920 standard output and standard error are both connected to a single pipe that is
19921 read by Exim. The &%max_output%& option controls how much output the command
19922 may produce, and the &%return_output%& and &%return_fail_output%& options
19923 control what is done with it.
19925 Not running the command under a shell (by default) lessens the security risks
19926 in cases when a command from a user's filter file is built out of data that was
19927 taken from an incoming message. If a shell is required, it can of course be
19928 explicitly specified as the command to be run. However, there are circumstances
19929 where existing commands (for example, in &_.forward_& files) expect to be run
19930 under a shell and cannot easily be modified. To allow for these cases, there is
19931 an option called &%use_shell%&, which changes the way the &(pipe)& transport
19932 works. Instead of breaking up the command line as just described, it expands it
19933 as a single string and passes the result to &_/bin/sh_&. The
19934 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
19935 with &%use_shell%&, and the whole mechanism is inherently less secure.
19939 .section "Environment variables" "SECTpipeenv"
19940 .cindex "&(pipe)& transport" "environment for command"
19941 .cindex "environment for pipe transport"
19942 The environment variables listed below are set up when the command is invoked.
19943 This list is a compromise for maximum compatibility with other MTAs. Note that
19944 the &%environment%& option can be used to add additional variables to this
19947 &`DOMAIN `& the domain of the address
19948 &`HOME `& the home directory, if set
19949 &`HOST `& the host name when called from a router (see below)
19950 &`LOCAL_PART `& see below
19951 &`LOCAL_PART_PREFIX `& see below
19952 &`LOCAL_PART_SUFFIX `& see below
19953 &`LOGNAME `& see below
19954 &`MESSAGE_ID `& Exim's local ID for the message
19955 &`PATH `& as specified by the &%path%& option below
19956 &`QUALIFY_DOMAIN `& the sender qualification domain
19957 &`RECIPIENT `& the complete recipient address
19958 &`SENDER `& the sender of the message (empty if a bounce)
19959 &`SHELL `& &`/bin/sh`&
19960 &`TZ `& the value of the &%timezone%& option, if set
19961 &`USER `& see below
19963 When a &(pipe)& transport is called directly from (for example) an &(accept)&
19964 router, LOCAL_PART is set to the local part of the address. When it is
19965 called as a result of a forward or alias expansion, LOCAL_PART is set to
19966 the local part of the address that was expanded. In both cases, any affixes are
19967 removed from the local part, and made available in LOCAL_PART_PREFIX and
19968 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
19969 same value as LOCAL_PART for compatibility with other MTAs.
19972 HOST is set only when a &(pipe)& transport is called from a router that
19973 associates hosts with an address, typically when using &(pipe)& as a
19974 pseudo-remote transport. HOST is set to the first host name specified by
19978 If the transport's generic &%home_directory%& option is set, its value is used
19979 for the HOME environment variable. Otherwise, a home directory may be set
19980 by the router's &%transport_home_directory%& option, which defaults to the
19981 user's home directory if &%check_local_user%& is set.
19984 .section "Private options for pipe"
19985 .cindex "options" "&(pipe)& transport"
19989 .option allow_commands pipe "string list&!!" unset
19990 .cindex "&(pipe)& transport" "permitted commands"
19991 The string is expanded, and is then interpreted as a colon-separated list of
19992 permitted commands. If &%restrict_to_path%& is not set, the only commands
19993 permitted are those in the &%allow_commands%& list. They need not be absolute
19994 paths; the &%path%& option is still used for relative paths. If
19995 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
19996 in the &%allow_commands%& list, or a name without any slashes that is found on
19997 the path. In other words, if neither &%allow_commands%& nor
19998 &%restrict_to_path%& is set, there is no restriction on the command, but
19999 otherwise only commands that are permitted by one or the other are allowed. For
20002 allow_commands = /usr/bin/vacation
20004 and &%restrict_to_path%& is not set, the only permitted command is
20005 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
20006 &%use_shell%& is set.
20009 .option batch_id pipe string&!! unset
20010 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20013 .option batch_max pipe integer 1
20014 This limits the number of addresses that can be handled in a single delivery.
20015 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20018 .option check_string pipe string unset
20019 As &(pipe)& writes the message, the start of each line is tested for matching
20020 &%check_string%&, and if it does, the initial matching characters are replaced
20021 by the contents of &%escape_string%&, provided both are set. The value of
20022 &%check_string%& is a literal string, not a regular expression, and the case of
20023 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
20024 of &%check_string%& and &%escape_string%& are forced to values that implement
20025 the SMTP escaping protocol. Any settings made in the configuration file are
20029 .option command pipe string&!! unset
20030 This option need not be set when &(pipe)& is being used to deliver to pipes
20031 obtained directly from address redirections. In other cases, the option must be
20032 set, to provide a command to be run. It need not yield an absolute path (see
20033 the &%path%& option below). The command is split up into separate arguments by
20034 Exim, and each argument is separately expanded, as described in section
20035 &<<SECThowcommandrun>>& above.
20038 .option environment pipe string&!! unset
20039 .cindex "&(pipe)& transport" "environment for command"
20040 .cindex "environment for &(pipe)& transport"
20041 This option is used to add additional variables to the environment in which the
20042 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
20043 a string which is expanded, and then interpreted as a colon-separated list of
20044 environment settings of the form <&'name'&>=<&'value'&>.
20047 .option escape_string pipe string unset
20048 See &%check_string%& above.
20051 .option freeze_exec_fail pipe boolean false
20052 .cindex "exec failure"
20053 .cindex "failure of exec"
20054 .cindex "&(pipe)& transport" "failure of exec"
20055 Failure to exec the command in a pipe transport is by default treated like
20056 any other failure while running the command. However, if &%freeze_exec_fail%&
20057 is set, failure to exec is treated specially, and causes the message to be
20058 frozen, whatever the setting of &%ignore_status%&.
20061 .option ignore_status pipe boolean false
20062 If this option is true, the status returned by the subprocess that is set up to
20063 run the command is ignored, and Exim behaves as if zero had been returned.
20064 Otherwise, a non-zero status or termination by signal causes an error return
20065 from the transport unless the status value is one of those listed in
20066 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
20068 &*Note*&: This option does not apply to timeouts, which do not return a status.
20069 See the &%timeout_defer%& option for how timeouts are handled.
20071 .option log_defer_output pipe boolean false
20072 .cindex "&(pipe)& transport" "logging output"
20073 If this option is set, and the status returned by the command is
20074 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
20075 and any output was produced, the first line of it is written to the main log.
20078 .option log_fail_output pipe boolean false
20079 If this option is set, and the command returns any output, and also ends with a
20080 return code that is neither zero nor one of the return codes listed in
20081 &%temp_errors%& (that is, the delivery failed), the first line of output is
20082 written to the main log. This option and &%log_output%& are mutually exclusive.
20083 Only one of them may be set.
20087 .option log_output pipe boolean false
20088 If this option is set and the command returns any output, the first line of
20089 output is written to the main log, whatever the return code. This option and
20090 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
20094 .option max_output pipe integer 20K
20095 This specifies the maximum amount of output that the command may produce on its
20096 standard output and standard error file combined. If the limit is exceeded, the
20097 process running the command is killed. This is intended as a safety measure to
20098 catch runaway processes. The limit is applied independently of the settings of
20099 the options that control what is done with such output (for example,
20100 &%return_output%&). Because of buffering effects, the amount of output may
20101 exceed the limit by a small amount before Exim notices.
20104 .option message_prefix pipe string&!! "see below"
20105 The string specified here is expanded and output at the start of every message.
20106 The default is unset if &%use_bsmtp%& is set. Otherwise it is
20109 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
20113 .cindex "&%tmail%&"
20114 .cindex "&""From""& line"
20115 This is required by the commonly used &_/usr/bin/vacation_& program.
20116 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
20117 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
20123 .option message_suffix pipe string&!! "see below"
20124 The string specified here is expanded and output at the end of every message.
20125 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
20126 The suffix can be suppressed by setting
20131 .option path pipe string &`/bin:/usr/bin`&
20132 This option specifies the string that is set up in the PATH environment
20133 variable of the subprocess. If the &%command%& option does not yield an
20134 absolute path name, the command is sought in the PATH directories, in the usual
20135 way. &*Warning*&: This does not apply to a command specified as a transport
20139 .option pipe_as_creator pipe boolean false
20140 .cindex "uid (user id)" "local delivery"
20141 If the generic &%user%& option is not set and this option is true, the delivery
20142 process is run under the uid that was in force when Exim was originally called
20143 to accept the message. If the group id is not otherwise set (via the generic
20144 &%group%& option), the gid that was in force when Exim was originally called to
20145 accept the message is used.
20148 .option restrict_to_path pipe boolean false
20149 When this option is set, any command name not listed in &%allow_commands%& must
20150 contain no slashes. The command is searched for only in the directories listed
20151 in the &%path%& option. This option is intended for use in the case when a pipe
20152 command has been generated from a user's &_.forward_& file. This is usually
20153 handled by a &(pipe)& transport called &%address_pipe%&.
20156 .option return_fail_output pipe boolean false
20157 If this option is true, and the command produced any output and ended with a
20158 return code other than zero or one of the codes listed in &%temp_errors%& (that
20159 is, the delivery failed), the output is returned in the bounce message.
20160 However, if the message has a null sender (that is, it is itself a bounce
20161 message), output from the command is discarded. This option and
20162 &%return_output%& are mutually exclusive. Only one of them may be set.
20166 .option return_output pipe boolean false
20167 If this option is true, and the command produced any output, the delivery is
20168 deemed to have failed whatever the return code from the command, and the output
20169 is returned in the bounce message. Otherwise, the output is just discarded.
20170 However, if the message has a null sender (that is, it is a bounce message),
20171 output from the command is always discarded, whatever the setting of this
20172 option. This option and &%return_fail_output%& are mutually exclusive. Only one
20173 of them may be set.
20177 .option temp_errors pipe "string list" "see below"
20178 .cindex "&(pipe)& transport" "temporary failure"
20179 This option contains either a colon-separated list of numbers, or a single
20180 asterisk. If &%ignore_status%& is false
20181 and &%return_output%& is not set,
20182 and the command exits with a non-zero return code, the failure is treated as
20183 temporary and the delivery is deferred if the return code matches one of the
20184 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
20185 codes are treated as permanent errors. The default setting contains the codes
20186 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
20187 compiled on a system that does not define these macros, it assumes values of 75
20188 and 73, respectively.
20191 .option timeout pipe time 1h
20192 If the command fails to complete within this time, it is killed. This normally
20193 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
20194 specifies no timeout. In order to ensure that any subprocesses created by the
20195 command are also killed, Exim makes the initial process a process group leader,
20196 and kills the whole process group on a timeout. However, this can be defeated
20197 if one of the processes starts a new process group.
20199 .option timeout_defer pipe boolean false
20200 A timeout in a &(pipe)& transport, either in the command that the transport
20201 runs, or in a transport filter that is associated with it, is by default
20202 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
20203 is set true, both kinds of timeout become temporary errors, causing the
20204 delivery to be deferred.
20206 .option umask pipe "octal integer" 022
20207 This specifies the umask setting for the subprocess that runs the command.
20210 .option use_bsmtp pipe boolean false
20211 .cindex "envelope sender"
20212 If this option is set true, the &(pipe)& transport writes messages in &"batch
20213 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
20214 commands. If you want to include a leading HELO command with such messages,
20215 you can do so by setting the &%message_prefix%& option. See section
20216 &<<SECTbatchSMTP>>& for details of batch SMTP.
20219 .option use_classresources pipe boolean false
20220 .cindex "class resources (BSD)"
20221 This option is available only when Exim is running on FreeBSD, NetBSD, or
20222 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
20223 resource limits when a &(pipe)& transport is run to perform a delivery. The
20224 limits for the uid under which the pipe is to run are obtained from the login
20229 .option use_crlf pipe boolean false
20230 .cindex "carriage return"
20232 This option causes lines to be terminated with the two-character CRLF sequence
20233 (carriage return, linefeed) instead of just a linefeed character. In the case
20234 of batched SMTP, the byte sequence written to the pipe is then an exact image
20235 of what would be sent down a real SMTP connection.
20237 The contents of the &%message_prefix%& and &%message_suffix%& options are
20238 written verbatim, so must contain their own carriage return characters if these
20239 are needed. Since the default values for both &%message_prefix%& and
20240 &%message_suffix%& end with a single linefeed, their values must be changed to
20241 end with &`\r\n`& if &%use_crlf%& is set.
20244 .option use_shell pipe boolean false
20245 .cindex "&$pipe_addresses$&"
20246 If this option is set, it causes the command to be passed to &_/bin/sh_&
20247 instead of being run directly from the transport, as described in section
20248 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
20249 where the command is expected to be run under a shell and cannot easily be
20250 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
20251 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
20252 command is expanded as a single string, and handed to &_/bin/sh_& as data for
20257 .section "Using an external local delivery agent"
20258 .cindex "local delivery" "using an external agent"
20259 .cindex "&'procmail'&"
20260 .cindex "external local delivery"
20261 .cindex "delivery" "&'procmail'&"
20262 .cindex "delivery" "by external agent"
20263 The &(pipe)& transport can be used to pass all messages that require local
20264 delivery to a separate local delivery agent such as &%procmail%&. When doing
20265 this, care must be taken to ensure that the pipe is run under an appropriate
20266 uid and gid. In some configurations one wants this to be a uid that is trusted
20267 by the delivery agent to supply the correct sender of the message. It may be
20268 necessary to recompile or reconfigure the delivery agent so that it trusts an
20269 appropriate user. The following is an example transport and router
20270 configuration for &%procmail%&:
20275 command = /usr/local/bin/procmail -d $local_part
20279 check_string = "From "
20280 escape_string = ">From "
20288 transport = procmail_pipe
20290 In this example, the pipe is run as the local user, but with the group set to
20291 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
20292 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
20293 user to supply a correct sender address. If you do not specify either a
20294 &%group%& or a &%user%& option, the pipe command is run as the local user. The
20295 home directory is the user's home directory by default.
20297 &*Note*&: The command that the pipe transport runs does &'not'& begin with
20301 as shown in some &%procmail%& documentation, because Exim does not by default
20302 use a shell to run pipe commands.
20305 The next example shows a transport and a router for a system where local
20306 deliveries are handled by the Cyrus IMAP server.
20309 local_delivery_cyrus:
20311 command = /usr/cyrus/bin/deliver \
20312 -m ${substr_1:$local_part_suffix} -- $local_part
20324 local_part_suffix = .*
20325 transport = local_delivery_cyrus
20327 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
20328 &%return_output%& to cause any text written by Cyrus to be returned to the
20330 .ecindex IIDpiptra1
20331 .ecindex IIDpiptra2
20334 . ////////////////////////////////////////////////////////////////////////////
20335 . ////////////////////////////////////////////////////////////////////////////
20337 .chapter "The smtp transport" "CHAPsmtptrans"
20338 .scindex IIDsmttra1 "transports" "&(smtp)&"
20339 .scindex IIDsmttra2 "&(smtp)& transport"
20340 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
20341 or LMTP protocol. The list of hosts to try can either be taken from the address
20342 that is being processed (having been set up by the router), or specified
20343 explicitly for the transport. Timeout and retry processing (see chapter
20344 &<<CHAPretry>>&) is applied to each IP address independently.
20347 .section "Multiple messages on a single connection"
20348 The sending of multiple messages over a single TCP/IP connection can arise in
20352 If a message contains more than &%max_rcpt%& (see below) addresses that are
20353 routed to the same host, more than one copy of the message has to be sent to
20354 that host. In this situation, multiple copies may be sent in a single run of
20355 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
20356 does when it has too many addresses to send in one message also depends on the
20357 value of the global &%remote_max_parallel%& option. Details are given in
20358 section &<<SECToutSMTPTCP>>&.)
20360 .cindex "hints database" "remembering routing"
20361 When a message has been successfully delivered over a TCP/IP connection, Exim
20362 looks in its hints database to see if there are any other messages awaiting a
20363 connection to the same host. If there are, a new delivery process is started
20364 for one of them, and the current TCP/IP connection is passed on to it. The new
20365 process may in turn send multiple copies and possibly create yet another
20370 For each copy sent over the same TCP/IP connection, a sequence counter is
20371 incremented, and if it ever gets to the value of &%connection_max_messages%&,
20372 no further messages are sent over that connection.
20376 .section "Use of the $host variable"
20378 .cindex "&$host_address$&"
20379 At the start of a run of the &(smtp)& transport, the values of &$host$& and
20380 &$host_address$& are the name and IP address of the first host on the host list
20381 passed by the router. However, when the transport is about to connect to a
20382 specific host, and while it is connected to that host, &$host$& and
20383 &$host_address$& are set to the values for that host. These are the values
20384 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
20385 &%serialize_hosts%&, and the various TLS options are expanded.
20389 .section "Private options for smtp"
20390 .cindex "options" "&(smtp)& transport"
20391 The private options of the &(smtp)& transport are as follows:
20394 .option allow_localhost smtp boolean false
20395 .cindex "local host" "sending to"
20396 .cindex "fallback" "hosts specified on transport"
20397 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
20398 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
20399 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
20400 the delivery anyway. This should be used only in special cases when the
20401 configuration ensures that no looping will result (for example, a differently
20402 configured Exim is listening on the port to which the message is sent).
20405 .option authenticated_sender smtp string&!! unset
20408 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
20409 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
20410 overriding any existing authenticated sender value. If the string expansion is
20411 forced to fail, the option is ignored. Other expansion failures cause delivery
20412 to be deferred. If the result of expansion is an empty string, that is also
20415 If the SMTP session is not authenticated, the expansion of
20416 &%authenticated_sender%& still happens (and can cause the delivery to be
20417 deferred if it fails), but no AUTH= item is added to MAIL commands
20418 unless &%authenticated_sender_force%& is true.
20421 This option allows you to use the &(smtp)& transport in LMTP mode to
20422 deliver mail to Cyrus IMAP and provide the proper local part as the
20423 &"authenticated sender"&, via a setting such as:
20425 authenticated_sender = $local_part
20427 This removes the need for IMAP subfolders to be assigned special ACLs to
20428 allow direct delivery to those subfolders.
20430 Because of expected uses such as that just described for Cyrus (when no
20431 domain is involved), there is no checking on the syntax of the provided
20436 .option authenticated_sender_force smtp boolean false
20437 If this option is set true, the &%authenticated_sender%& option's value
20438 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
20439 authenticated as a client.
20443 .option command_timeout smtp time 5m
20444 This sets a timeout for receiving a response to an SMTP command that has been
20445 sent out. It is also used when waiting for the initial banner line from the
20446 remote host. Its value must not be zero.
20449 .option connect_timeout smtp time 5m
20450 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
20451 to a remote host. A setting of zero allows the system timeout (typically
20452 several minutes) to act. To have any effect, the value of this option must be
20453 less than the system timeout. However, it has been observed that on some
20454 systems there is no system timeout, which is why the default value for this
20455 option is 5 minutes, a value recommended by RFC 1123.
20458 .option connection_max_messages smtp integer 500
20459 .cindex "SMTP" "passed connection"
20460 .cindex "SMTP" "multiple deliveries"
20461 .cindex "multiple SMTP deliveries"
20462 This controls the maximum number of separate message deliveries that are sent
20463 over a single TCP/IP connection. If the value is zero, there is no limit.
20464 For testing purposes, this value can be overridden by the &%-oB%& command line
20468 .option data_timeout smtp time 5m
20469 This sets a timeout for the transmission of each block in the data portion of
20470 the message. As a result, the overall timeout for a message depends on the size
20471 of the message. Its value must not be zero. See also &%final_timeout%&.
20474 .option delay_after_cutoff smtp boolean true
20475 This option controls what happens when all remote IP addresses for a given
20476 domain have been inaccessible for so long that they have passed their retry
20479 In the default state, if the next retry time has not been reached for any of
20480 them, the address is bounced without trying any deliveries. In other words,
20481 Exim delays retrying an IP address after the final cutoff time until a new
20482 retry time is reached, and can therefore bounce an address without ever trying
20483 a delivery, when machines have been down for a long time. Some people are
20484 unhappy at this prospect, so...
20486 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
20487 addresses are past their final cutoff time, Exim tries to deliver to those
20488 IP addresses that have not been tried since the message arrived. If there are
20489 none, of if they all fail, the address is bounced. In other words, it does not
20490 delay when a new message arrives, but immediately tries those expired IP
20491 addresses that haven't been tried since the message arrived. If there is a
20492 continuous stream of messages for the dead hosts, unsetting
20493 &%delay_after_cutoff%& means that there will be many more attempts to deliver
20497 .option dns_qualify_single smtp boolean true
20498 If the &%hosts%& or &%fallback_hosts%& option is being used,
20499 and the &%gethostbyname%& option is false,
20500 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
20501 in chapter &<<CHAPdnslookup>>& for more details.
20504 .option dns_search_parents smtp boolean false
20505 .cindex "&%search_parents%&"
20506 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
20507 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
20508 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
20513 .option fallback_hosts smtp "string list" unset
20514 .cindex "fallback" "hosts specified on transport"
20515 String expansion is not applied to this option. The argument must be a
20516 colon-separated list of host names or IP addresses, optionally also including
20517 port numbers, though the separator can be changed, as described in section
20518 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
20519 item in a &%route_list%& setting for the &(manualroute)& router, as described
20520 in section &<<SECTformatonehostitem>>&.
20522 Fallback hosts can also be specified on routers, which associate them with the
20523 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
20524 &%fallback_hosts%& specified on the transport is used only if the address does
20525 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
20526 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
20527 However, &%hosts_randomize%& does apply to fallback host lists.
20529 If Exim is unable to deliver to any of the hosts for a particular address, and
20530 the errors are not permanent rejections, the address is put on a separate
20531 transport queue with its host list replaced by the fallback hosts, unless the
20532 address was routed via MX records and the current host was in the original MX
20533 list. In that situation, the fallback host list is not used.
20535 Once normal deliveries are complete, the fallback queue is delivered by
20536 re-running the same transports with the new host lists. If several failing
20537 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
20538 copy of the message is sent.
20540 The resolution of the host names on the fallback list is controlled by the
20541 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
20542 both to cases when the host list comes with the address and when it is taken
20543 from &%hosts%&. This option provides a &"use a smart host only if delivery
20547 .option final_timeout smtp time 10m
20548 This is the timeout that applies while waiting for the response to the final
20549 line containing just &"."& that terminates a message. Its value must not be
20553 .option gethostbyname smtp boolean false
20554 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
20555 being used, names are looked up using &[gethostbyname()]&
20556 (or &[getipnodebyname()]& when available)
20557 instead of using the DNS. Of course, that function may in fact use the DNS, but
20558 it may also consult other sources of information such as &_/etc/hosts_&.
20560 .option helo_data smtp string&!! &`$primary_hostname`&
20561 .cindex "HELO argument" "setting"
20562 .cindex "EHLO argument" "setting"
20563 The value of this option is expanded, and used as the argument for the EHLO or
20564 HELO command that starts the outgoing SMTP session. The variables &$host$& and
20565 &$host_address$& are set to the identity of the remote host, and can be used to
20566 generate different values for different servers.
20568 .option hosts smtp "string list&!!" unset
20569 Hosts are associated with an address by a router such as &(dnslookup)&, which
20570 finds the hosts by looking up the address domain in the DNS, or by
20571 &(manualroute)&, which has lists of hosts in its configuration. However,
20572 email addresses can be passed to the &(smtp)& transport by any router, and not
20573 all of them can provide an associated list of hosts.
20575 The &%hosts%& option specifies a list of hosts to be used if the address being
20576 processed does not have any hosts associated with it. The hosts specified by
20577 &%hosts%& are also used, whether or not the address has its own hosts, if
20578 &%hosts_override%& is set.
20580 The string is first expanded, before being interpreted as a colon-separated
20581 list of host names or IP addresses, possibly including port numbers. The
20582 separator may be changed to something other than colon, as described in section
20583 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
20584 item in a &%route_list%& setting for the &(manualroute)& router, as described
20585 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
20586 of the &(manualroute)& router is not available here.
20588 If the expansion fails, delivery is deferred. Unless the failure was caused by
20589 the inability to complete a lookup, the error is logged to the panic log as
20590 well as the main log. Host names are looked up either by searching directly for
20591 address records in the DNS or by calling &[gethostbyname()]& (or
20592 &[getipnodebyname()]& when available), depending on the setting of the
20593 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
20594 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
20597 During delivery, the hosts are tried in order, subject to their retry status,
20598 unless &%hosts_randomize%& is set.
20601 .option hosts_avoid_esmtp smtp "host list&!!" unset
20602 .cindex "ESMTP" "avoiding use of"
20603 .cindex "HELO" "forcing use of"
20604 .cindex "EHLO" "avoiding use of"
20605 .cindex "PIPELINING" "avoiding the use of"
20606 This option is for use with broken hosts that announce ESMTP facilities (for
20607 example, PIPELINING) and then fail to implement them properly. When a host
20608 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
20609 start of the SMTP session. This means that it cannot use any of the ESMTP
20610 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
20613 .option hosts_avoid_tls smtp "host list&!!" unset
20614 .cindex "TLS" "avoiding for certain hosts"
20615 Exim will not try to start a TLS session when delivering to any host that
20616 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
20619 .option hosts_max_try smtp integer 5
20620 .cindex "host" "maximum number to try"
20621 .cindex "limit" "number of hosts tried"
20622 .cindex "limit" "number of MX tried"
20623 .cindex "MX record" "maximum tried"
20624 This option limits the number of IP addresses that are tried for any one
20625 delivery in cases where there are temporary delivery errors. Section
20626 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
20629 .option hosts_max_try_hardlimit smtp integer 50
20630 This is an additional check on the maximum number of IP addresses that Exim
20631 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
20636 .option hosts_nopass_tls smtp "host list&!!" unset
20637 .cindex "TLS" "passing connection"
20638 .cindex "multiple SMTP deliveries"
20639 .cindex "TLS" "multiple message deliveries"
20640 For any host that matches this list, a connection on which a TLS session has
20641 been started will not be passed to a new delivery process for sending another
20642 message on the same connection. See section &<<SECTmulmessam>>& for an
20643 explanation of when this might be needed.
20646 .option hosts_override smtp boolean false
20647 If this option is set and the &%hosts%& option is also set, any hosts that are
20648 attached to the address are ignored, and instead the hosts specified by the
20649 &%hosts%& option are always used. This option does not apply to
20650 &%fallback_hosts%&.
20653 .option hosts_randomize smtp boolean false
20654 .cindex "randomized host list"
20655 .cindex "host" "list of; randomized"
20656 .cindex "fallback" "randomized hosts"
20657 If this option is set, and either the list of hosts is taken from the
20658 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
20659 were not obtained from MX records (this includes fallback hosts from the
20660 router), and were not randomizied by the router, the order of trying the hosts
20661 is randomized each time the transport runs. Randomizing the order of a host
20662 list can be used to do crude load sharing.
20664 When &%hosts_randomize%& is true, a host list may be split into groups whose
20665 order is separately randomized. This makes it possible to set up MX-like
20666 behaviour. The boundaries between groups are indicated by an item that is just
20667 &`+`& in the host list. For example:
20669 hosts = host1:host2:host3:+:host4:host5
20671 The order of the first three hosts and the order of the last two hosts is
20672 randomized for each use, but the first three always end up before the last two.
20673 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
20675 .option hosts_require_auth smtp "host list&!!" unset
20676 .cindex "authentication" "required by client"
20677 This option provides a list of servers for which authentication must succeed
20678 before Exim will try to transfer a message. If authentication fails for
20679 servers which are not in this list, Exim tries to send unauthenticated. If
20680 authentication fails for one of these servers, delivery is deferred. This
20681 temporary error is detectable in the retry rules, so it can be turned into a
20682 hard failure if required. See also &%hosts_try_auth%&, and chapter
20683 &<<CHAPSMTPAUTH>>& for details of authentication.
20686 .option hosts_require_tls smtp "host list&!!" unset
20687 .cindex "TLS" "requiring for certain servers"
20688 Exim will insist on using a TLS session when delivering to any host that
20689 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
20690 &*Note*&: This option affects outgoing mail only. To insist on TLS for
20691 incoming messages, use an appropriate ACL.
20693 .option hosts_try_auth smtp "host list&!!" unset
20694 .cindex "authentication" "optional in client"
20695 This option provides a list of servers to which, provided they announce
20696 authentication support, Exim will attempt to authenticate as a client when it
20697 connects. If authentication fails, Exim will try to transfer the message
20698 unauthenticated. See also &%hosts_require_auth%&, and chapter
20699 &<<CHAPSMTPAUTH>>& for details of authentication.
20701 .option interface smtp "string list&!!" unset
20702 .cindex "bind IP address"
20703 .cindex "IP address" "binding"
20705 .cindex "&$host_address$&"
20706 This option specifies which interface to bind to when making an outgoing SMTP
20707 call. The variables &$host$& and &$host_address$& refer to the host to which a
20708 connection is about to be made during the expansion of the string. Forced
20709 expansion failure, or an empty string result causes the option to be ignored.
20710 Otherwise, after expansion,
20711 the string must be a list of IP addresses, colon-separated by default, but the
20712 separator can be changed in the usual way.
20715 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
20717 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
20718 connection. If none of them are the correct type, the option is ignored. If
20719 &%interface%& is not set, or is ignored, the system's IP functions choose which
20720 interface to use if the host has more than one.
20723 .option keepalive smtp boolean true
20724 .cindex "keepalive" "on outgoing connection"
20725 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
20726 connections. When set, it causes the kernel to probe idle connections
20727 periodically, by sending packets with &"old"& sequence numbers. The other end
20728 of the connection should send a acknowledgement if the connection is still okay
20729 or a reset if the connection has been aborted. The reason for doing this is
20730 that it has the beneficial effect of freeing up certain types of connection
20731 that can get stuck when the remote host is disconnected without tidying up the
20732 TCP/IP call properly. The keepalive mechanism takes several hours to detect
20736 .option lmtp_ignore_quota smtp boolean false
20737 .cindex "LMTP" "ignoring quota errors"
20738 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
20739 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
20740 has advertised support for IGNOREQUOTA in its response to the LHLO command.
20742 .option max_rcpt smtp integer 100
20743 .cindex "RCPT" "maximum number of outgoing"
20744 This option limits the number of RCPT commands that are sent in a single
20745 SMTP message transaction. Each set of addresses is treated independently, and
20746 so can cause parallel connections to the same host if &%remote_max_parallel%&
20750 .option multi_domain smtp boolean true
20751 .cindex "&$domain$&"
20752 When this option is set, the &(smtp)& transport can handle a number of
20753 addresses containing a mixture of different domains provided they all resolve
20754 to the same list of hosts. Turning the option off restricts the transport to
20755 handling only one domain at a time. This is useful if you want to use
20756 &$domain$& in an expansion for the transport, because it is set only when there
20757 is a single domain involved in a remote delivery.
20760 .option port smtp string&!! "see below"
20761 .cindex "port" "sending TCP/IP"
20762 .cindex "TCP/IP" "setting outgoing port"
20763 This option specifies the TCP/IP port on the server to which Exim connects. If
20764 it begins with a digit it is taken as a port number; otherwise it is looked up
20765 using &[getservbyname()]&. The default value is normally &"smtp"&, but if
20766 &%protocol%& is set to &"lmtp"&, the default is &"lmtp"&.
20767 If the expansion fails, or if a port number cannot be found, delivery is
20772 .option protocol smtp string smtp
20773 .cindex "LMTP" "over TCP/IP"
20774 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
20775 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
20776 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
20777 deliveries into closed message stores. Exim also has support for running LMTP
20778 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
20781 .option retry_include_ip_address smtp boolean true
20782 Exim normally includes both the host name and the IP address in the key it
20783 constructs for indexing retry data after a temporary delivery failure. This
20784 means that when one of several IP addresses for a host is failing, it gets
20785 tried periodically (controlled by the retry rules), but use of the other IP
20786 addresses is not affected.
20788 However, in some dialup environments hosts are assigned a different IP address
20789 each time they connect. In this situation the use of the IP address as part of
20790 the retry key leads to undesirable behaviour. Setting this option false causes
20791 Exim to use only the host name. This should normally be done on a separate
20792 instance of the &(smtp)& transport, set up specially to handle the dialup
20796 .option serialize_hosts smtp "host list&!!" unset
20797 .cindex "serializing connections"
20798 .cindex "host" "serializing connections"
20799 Because Exim operates in a distributed manner, if several messages for the same
20800 host arrive at around the same time, more than one simultaneous connection to
20801 the remote host can occur. This is not usually a problem except when there is a
20802 slow link between the hosts. In that situation it may be helpful to restrict
20803 Exim to one connection at a time. This can be done by setting
20804 &%serialize_hosts%& to match the relevant hosts.
20806 .cindex "hints database" "serializing deliveries to a host"
20807 Exim implements serialization by means of a hints database in which a record is
20808 written whenever a process connects to one of the restricted hosts. The record
20809 is deleted when the connection is completed. Obviously there is scope for
20810 records to get left lying around if there is a system or program crash. To
20811 guard against this, Exim ignores any records that are more than six hours old.
20813 If you set up this kind of serialization, you should also arrange to delete the
20814 relevant hints database whenever your system reboots. The names of the files
20815 start with &_misc_& and they are kept in the &_spool/db_& directory. There
20816 may be one or two files, depending on the type of DBM in use. The same files
20817 are used for ETRN serialization.
20820 .option size_addition smtp integer 1024
20821 .cindex "SMTP" "SIZE"
20822 .cindex "message" "size issue for transport filter"
20823 .cindex "size" "of message"
20824 .cindex "transport" "filter"
20825 .cindex "filter" "transport filter"
20826 If a remote SMTP server indicates that it supports the SIZE option of the
20827 MAIL command, Exim uses this to pass over the message size at the start of
20828 an SMTP transaction. It adds the value of &%size_addition%& to the value it
20829 sends, to allow for headers and other text that may be added during delivery by
20830 configuration options or in a transport filter. It may be necessary to increase
20831 this if a lot of text is added to messages.
20833 Alternatively, if the value of &%size_addition%& is set negative, it disables
20834 the use of the SIZE option altogether.
20837 .option tls_certificate smtp string&!! unset
20838 .cindex "TLS client certificate" "location of"
20839 .cindex "certificate for client" "location of"
20841 .cindex "&$host_address$&"
20842 The value of this option must be the absolute path to a file which contains the
20843 client's certificate, for possible use when sending a message over an encrypted
20844 connection. The values of &$host$& and &$host_address$& are set to the name and
20845 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
20848 &*Note*&: This option must be set if you want Exim to be able to use a TLS
20849 certificate when sending messages as a client. The global option of the same
20850 name specifies the certificate for Exim as a server; it is not automatically
20851 assumed that the same certificate should be used when Exim is operating as a
20855 .option tls_crl smtp string&!! unset
20856 .cindex "TLS" "client certificate revocation list"
20857 .cindex "certificate" "revocation list for client"
20858 This option specifies a certificate revocation list. The expanded value must
20859 be the name of a file that contains a CRL in PEM format.
20862 .option tls_privatekey smtp string&!! unset
20863 .cindex "TLS client private key" "location of"
20865 .cindex "&$host_address$&"
20867 The value of this option must be the absolute path to a file which contains the
20868 client's private key. This is used when sending a message over an encrypted
20869 connection using a client certificate. The values of &$host$& and
20870 &$host_address$& are set to the name and address of the server during the
20871 expansion. If this option is unset, or the expansion is forced to fail, or the
20872 result is an empty string, the private key is assumed to be in the same file as
20873 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
20877 .option tls_require_ciphers smtp string&!! unset
20878 .cindex "TLS" "requiring specific ciphers"
20879 .cindex "cipher" "requiring specific"
20881 .cindex "&$host_address$&"
20882 The value of this option must be a list of permitted cipher suites, for use
20883 when setting up an outgoing encrypted connection. (There is a global option of
20884 the same name for controlling incoming connections.) The values of &$host$& and
20885 &$host_address$& are set to the name and address of the server during the
20886 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
20887 is used in different ways by OpenSSL and GnuTLS (see sections
20888 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
20889 ciphers is a preference order.
20893 .option tls_tempfail_tryclear smtp boolean true
20894 When the server host is not in &%hosts_require_tls%&, and there is a problem in
20895 setting up a TLS session, this option determines whether or not Exim should try
20896 to deliver the message unencrypted. If it is set false, delivery to the
20897 current host is deferred; if there are other hosts, they are tried. If this
20898 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
20899 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
20900 TLS negotiation fails, Exim closes the current connection (because it is in an
20901 unknown state), opens a new one to the same host, and then tries the delivery
20905 .option tls_verify_certificates smtp string&!! unset
20906 .cindex "TLS" "server certificate verification"
20907 .cindex "certificate" "verification of server"
20909 .cindex "&$host_address$&"
20910 The value of this option must be the absolute path to a file containing
20911 permitted server certificates, for use when setting up an encrypted connection.
20912 Alternatively, if you are using OpenSSL, you can set
20913 &%tls_verify_certificates%& to the name of a directory containing certificate
20914 files. This does not work with GnuTLS; the option must be set to the name of a
20915 single file if you are using GnuTLS. The values of &$host$& and
20916 &$host_address$& are set to the name and address of the server during the
20917 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
20922 .section "How the limits for the number of hosts to try are used" &&&
20924 .cindex "host" "maximum number to try"
20925 .cindex "limit" "hosts; maximum number tried"
20926 There are two options that are concerned with the number of hosts that are
20927 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
20928 &%hosts_max_try_hardlimit%&.
20931 The &%hosts_max_try%& option limits the number of hosts that are tried
20932 for a single delivery. However, despite the term &"host"& in its name, the
20933 option actually applies to each IP address independently. In other words, a
20934 multihomed host is treated as several independent hosts, just as it is for
20937 Many of the larger ISPs have multiple MX records which often point to
20938 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
20939 created as a result of routing one of these domains.
20941 Trying every single IP address on such a long list does not seem sensible; if
20942 several at the top of the list fail, it is reasonable to assume there is some
20943 problem that is likely to affect all of them. Roughly speaking, the value of
20944 &%hosts_max_try%& is the maximum number that are tried before deferring the
20945 delivery. However, the logic cannot be quite that simple.
20947 Firstly, IP addresses that are skipped because their retry times have not
20948 arrived do not count, and in addition, addresses that are past their retry
20949 limits are also not counted, even when they are tried. This means that when
20950 some IP addresses are past their retry limits, more than the value of
20951 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
20952 that all IP addresses are considered before timing out an email address (but
20953 see below for an exception).
20955 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
20956 list to see if there is a subsequent host with a different (higher valued) MX.
20957 If there is, that host is considered next, and the current IP address is used
20958 but not counted. This behaviour helps in the case of a domain with a retry rule
20959 that hardly ever delays any hosts, as is now explained:
20961 Consider the case of a long list of hosts with one MX value, and a few with a
20962 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
20963 hosts at the top of the list are tried at first. With the default retry rule,
20964 which specifies increasing retry times, the higher MX hosts are eventually
20965 tried when those at the top of the list are skipped because they have not
20966 reached their retry times.
20968 However, it is common practice to put a fixed short retry time on domains for
20969 large ISPs, on the grounds that their servers are rarely down for very long.
20970 Unfortunately, these are exactly the domains that tend to resolve to long lists
20971 of hosts. The short retry time means that the lowest MX hosts are tried every
20972 time. The attempts may be in a different order because of random sorting, but
20973 without the special MX check, the higher MX hosts would never be tried until
20974 all the lower MX hosts had timed out (which might be several days), because
20975 there are always some lower MX hosts that have reached their retry times. With
20976 the special check, Exim considers at least one IP address from each MX value at
20977 every delivery attempt, even if the &%hosts_max_try%& limit has already been
20980 The above logic means that &%hosts_max_try%& is not a hard limit, and in
20981 particular, Exim normally eventually tries all the IP addresses before timing
20982 out an email address. When &%hosts_max_try%& was implemented, this seemed a
20983 reasonable thing to do. Recently, however, some lunatic DNS configurations have
20984 been set up with hundreds of IP addresses for some domains. It can
20985 take a very long time indeed for an address to time out in these cases.
20987 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
20988 Exim never tries more than this number of IP addresses; if it hits this limit
20989 and they are all timed out, the email address is bounced, even though not all
20990 possible IP addresses have been tried.
20991 .ecindex IIDsmttra1
20992 .ecindex IIDsmttra2
20998 . ////////////////////////////////////////////////////////////////////////////
20999 . ////////////////////////////////////////////////////////////////////////////
21001 .chapter "Address rewriting" "CHAPrewrite"
21002 .scindex IIDaddrew "rewriting" "addresses"
21003 There are some circumstances in which Exim automatically rewrites domains in
21004 addresses. The two most common are when an address is given without a domain
21005 (referred to as an &"unqualified address"&) or when an address contains an
21006 abbreviated domain that is expanded by DNS lookup.
21008 Unqualified envelope addresses are accepted only for locally submitted
21009 messages, or for messages that are received from hosts matching
21010 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
21011 appropriate. Unqualified addresses in header lines are qualified if they are in
21012 locally submitted messages, or messages from hosts that are permitted to send
21013 unqualified envelope addresses. Otherwise, unqualified addresses in header
21014 lines are neither qualified nor rewritten.
21016 One situation in which Exim does &'not'& automatically rewrite a domain is
21017 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
21018 such a domain should be rewritten using the &"canonical"& name, and some MTAs
21019 do this. The new RFCs do not contain this suggestion.
21022 .section "Explicitly configured address rewriting"
21023 This chapter describes the rewriting rules that can be used in the
21024 main rewrite section of the configuration file, and also in the generic
21025 &%headers_rewrite%& option that can be set on any transport.
21027 Some people believe that configured address rewriting is a Mortal Sin.
21028 Others believe that life is not possible without it. Exim provides the
21029 facility; you do not have to use it.
21031 The main rewriting rules that appear in the &"rewrite"& section of the
21032 configuration file are applied to addresses in incoming messages, both envelope
21033 addresses and addresses in header lines. Each rule specifies the types of
21034 address to which it applies.
21036 Rewriting of addresses in header lines applies only to those headers that
21037 were received with the message, and, in the case of transport rewriting, those
21038 that were added by a system filter. That is, it applies only to those headers
21039 that are common to all copies of the message. Header lines that are added by
21040 individual routers or transports (and which are therefore specific to
21041 individual recipient addresses) are not rewritten.
21043 In general, rewriting addresses from your own system or domain has some
21044 legitimacy. Rewriting other addresses should be done only with great care and
21045 in special circumstances. The author of Exim believes that rewriting should be
21046 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
21047 Although it can sometimes be used as a routing tool, this is very strongly
21050 There are two commonly encountered circumstances where rewriting is used, as
21051 illustrated by these examples:
21054 The company whose domain is &'hitch.fict.example'& has a number of hosts that
21055 exchange mail with each other behind a firewall, but there is only a single
21056 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
21057 &'hitch.fict.example'& when sending mail off-site.
21059 A host rewrites the local parts of its own users so that, for example,
21060 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
21065 .section "When does rewriting happen?"
21066 .cindex "rewriting" "timing of"
21067 .cindex "&ACL;" "rewriting addresses in"
21068 Configured address rewriting can take place at several different stages of a
21069 message's processing.
21071 .cindex "&$sender_address$&"
21072 At the start of an ACL for MAIL, the sender address may have been rewritten
21073 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
21074 ordinary rewrite rules have yet been applied. If, however, the sender address
21075 is verified in the ACL, it is rewritten before verification, and remains
21076 rewritten thereafter. The subsequent value of &$sender_address$& is the
21077 rewritten address. This also applies if sender verification happens in a
21078 RCPT ACL. Otherwise, when the sender address is not verified, it is
21079 rewritten as soon as a message's header lines have been received.
21081 .cindex "&$domain$&"
21082 .cindex "&$local_part$&"
21083 Similarly, at the start of an ACL for RCPT, the current recipient's address
21084 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
21085 rewrite rules have yet been applied to it. However, the behaviour is different
21086 from the sender address when a recipient is verified. The address is rewritten
21087 for the verification, but the rewriting is not remembered at this stage. The
21088 value of &$local_part$& and &$domain$& after verification are always the same
21089 as they were before (that is, they contain the unrewritten &-- except for
21090 SMTP-time rewriting &-- address).
21093 As soon as a message's header lines have been received, all the envelope
21094 recipient addresses are permanently rewritten, and rewriting is also applied to
21095 the addresses in the header lines (if configured). This happens before adding
21096 any header lines that were specified in MAIL or RCPT ACLs, and
21097 .cindex "&[local_scan()]& function" "address rewriting; timing of"
21098 before the DATA ACL and &[local_scan()]& functions are run.
21101 When an address is being routed, either for delivery or for verification,
21102 rewriting is applied immediately to child addresses that are generated by
21103 redirection, unless &%no_rewrite%& is set on the router.
21106 .cindex "envelope sender" "rewriting at transport time"
21107 .cindex "rewriting" "at transport time"
21108 .cindex "header lines" "rewriting at transport time"
21109 At transport time, additional rewriting of addresses in header lines can be
21110 specified by setting the generic &%headers_rewrite%& option on a transport.
21111 This option contains rules that are identical in form to those in the rewrite
21112 section of the configuration file. They are applied to the original message
21113 header lines and any that were added by ACLs or a system filter. They are not
21114 applied to header lines that are added by routers or the transport.
21116 The outgoing envelope sender can be rewritten by means of the &%return_path%&
21117 transport option. However, it is not possible to rewrite envelope recipients at
21124 .section "Testing the rewriting rules that apply on input"
21125 .cindex "rewriting" "testing"
21126 .cindex "testing" "rewriting"
21127 Exim's input rewriting configuration appears in a part of the run time
21128 configuration file headed by &"begin rewrite"&. It can be tested by the
21129 &%-brw%& command line option. This takes an address (which can be a full RFC
21130 2822 address) as its argument. The output is a list of how the address would be
21131 transformed by the rewriting rules for each of the different places it might
21132 appear in an incoming message, that is, for each different header and for the
21133 envelope sender and recipient fields. For example,
21135 exim -brw ph10@exim.workshop.example
21137 might produce the output
21139 sender: Philip.Hazel@exim.workshop.example
21140 from: Philip.Hazel@exim.workshop.example
21141 to: ph10@exim.workshop.example
21142 cc: ph10@exim.workshop.example
21143 bcc: ph10@exim.workshop.example
21144 reply-to: Philip.Hazel@exim.workshop.example
21145 env-from: Philip.Hazel@exim.workshop.example
21146 env-to: ph10@exim.workshop.example
21148 which shows that rewriting has been set up for that address when used in any of
21149 the source fields, but not when it appears as a recipient address. At the
21150 present time, there is no equivalent way of testing rewriting rules that are
21151 set for a particular transport.
21154 .section "Rewriting rules"
21155 .cindex "rewriting" "rules"
21156 The rewrite section of the configuration file consists of lines of rewriting
21159 <&'source pattern'&> <&'replacement'&> <&'flags'&>
21161 Rewriting rules that are specified for the &%headers_rewrite%& generic
21162 transport option are given as a colon-separated list. Each item in the list
21163 takes the same form as a line in the main rewriting configuration (except that
21164 any colons must be doubled, of course).
21166 The formats of source patterns and replacement strings are described below.
21167 Each is terminated by white space, unless enclosed in double quotes, in which
21168 case normal quoting conventions apply inside the quotes. The flags are single
21169 characters which may appear in any order. Spaces and tabs between them are
21172 For each address that could potentially be rewritten, the rules are scanned in
21173 order, and replacements for the address from earlier rules can themselves be
21174 replaced by later rules (but see the &"q"& and &"R"& flags).
21176 The order in which addresses are rewritten is undefined, may change between
21177 releases, and must not be relied on, with one exception: when a message is
21178 received, the envelope sender is always rewritten first, before any header
21179 lines are rewritten. For example, the replacement string for a rewrite of an
21180 address in &'To:'& must not assume that the message's address in &'From:'& has
21181 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
21182 that the envelope sender has already been rewritten.
21184 .cindex "&$domain$&"
21185 .cindex "&$local_part$&"
21186 The variables &$local_part$& and &$domain$& can be used in the replacement
21187 string to refer to the address that is being rewritten. Note that lookup-driven
21188 rewriting can be done by a rule of the form
21192 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
21193 refer to the address that is being rewritten.
21196 .section "Rewriting patterns"
21197 .cindex "rewriting" "patterns"
21198 .cindex "address list" "in a rewriting pattern"
21199 The source pattern in a rewriting rule is any item which may appear in an
21200 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
21201 single-item address list, which means that it is expanded before being tested
21202 against the address. As always, if you use a regular expression as a pattern,
21203 you must take care to escape dollar and backslash characters, or use the &`\N`&
21204 facility to suppress string expansion within the regular expression.
21206 Domains in patterns should be given in lower case. Local parts in patterns are
21207 case-sensitive. If you want to do case-insensitive matching of local parts, you
21208 can use a regular expression that starts with &`^(?i)`&.
21210 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
21211 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
21212 depending on the type of match which occurred. These can be used in the
21213 replacement string to insert portions of the incoming address. &$0$& always
21214 refers to the complete incoming address. When a regular expression is used, the
21215 numerical variables are set from its capturing subexpressions. For other types
21216 of pattern they are set as follows:
21219 If a local part or domain starts with an asterisk, the numerical variables
21220 refer to the character strings matched by asterisks, with &$1$& associated with
21221 the first asterisk, and &$2$& with the second, if present. For example, if the
21224 *queen@*.fict.example
21226 is matched against the address &'hearts-queen@wonderland.fict.example'& then
21228 $0 = hearts-queen@wonderland.fict.example
21232 Note that if the local part does not start with an asterisk, but the domain
21233 does, it is &$1$& that contains the wild part of the domain.
21236 If the domain part of the pattern is a partial lookup, the wild and fixed parts
21237 of the domain are placed in the next available numerical variables. Suppose,
21238 for example, that the address &'foo@bar.baz.example'& is processed by a
21239 rewriting rule of the form
21241 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
21243 and the key in the file that matches the domain is &`*.baz.example`&. Then
21249 If the address &'foo@baz.example'& is looked up, this matches the same
21250 wildcard file entry, and in this case &$2$& is set to the empty string, but
21251 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
21252 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
21253 whole domain. For non-partial domain lookups, no numerical variables are set.
21257 .section "Rewriting replacements"
21258 .cindex "rewriting" "replacements"
21259 If the replacement string for a rule is a single asterisk, addresses that
21260 match the pattern and the flags are &'not'& rewritten, and no subsequent
21261 rewriting rules are scanned. For example,
21263 hatta@lookingglass.fict.example * f
21265 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
21268 .cindex "&$domain$&"
21269 .cindex "&$local_part$&"
21270 If the replacement string is not a single asterisk, it is expanded, and must
21271 yield a fully qualified address. Within the expansion, the variables
21272 &$local_part$& and &$domain$& refer to the address that is being rewritten.
21273 Any letters they contain retain their original case &-- they are not lower
21274 cased. The numerical variables are set up according to the type of pattern that
21275 matched the address, as described above. If the expansion is forced to fail by
21276 the presence of &"fail"& in a conditional or lookup item, rewriting by the
21277 current rule is abandoned, but subsequent rules may take effect. Any other
21278 expansion failure causes the entire rewriting operation to be abandoned, and an
21279 entry written to the panic log.
21283 .section "Rewriting flags"
21284 There are three different kinds of flag that may appear on rewriting rules:
21287 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
21290 A flag that specifies rewriting at SMTP time: S.
21292 Flags that control the rewriting process: Q, q, R, w.
21295 For rules that are part of the &%headers_rewrite%& generic transport option,
21296 E, F, T, and S are not permitted.
21300 .section "Flags specifying which headers and envelope addresses to rewrite"
21301 .cindex "rewriting" "flags"
21302 If none of the following flag letters, nor the &"S"& flag (see section
21303 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
21304 and to both the sender and recipient fields of the envelope, whereas a
21305 transport-time rewriting rule just applies to all headers. Otherwise, the
21306 rewriting rule is skipped unless the relevant addresses are being processed.
21308 &`E`& rewrite all envelope fields
21309 &`F`& rewrite the envelope From field
21310 &`T`& rewrite the envelope To field
21311 &`b`& rewrite the &'Bcc:'& header
21312 &`c`& rewrite the &'Cc:'& header
21313 &`f`& rewrite the &'From:'& header
21314 &`h`& rewrite all headers
21315 &`r`& rewrite the &'Reply-To:'& header
21316 &`s`& rewrite the &'Sender:'& header
21317 &`t`& rewrite the &'To:'& header
21319 You should be particularly careful about rewriting &'Sender:'& headers, and
21320 restrict this to special known cases in your own domains.
21323 .section "The SMTP-time rewriting flag" "SECTrewriteS"
21324 .cindex "SMTP" "rewriting malformed addresses"
21325 .cindex "RCPT" "rewriting argument of"
21326 .cindex "MAIL" "rewriting argument of"
21327 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
21328 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
21329 before any other processing; even before syntax checking. The pattern is
21330 required to be a regular expression, and it is matched against the whole of the
21331 data for the command, including any surrounding angle brackets.
21333 .cindex "&$domain$&"
21334 .cindex "&$local_part$&"
21335 This form of rewrite rule allows for the handling of addresses that are not
21336 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
21337 input). Because the input is not required to be a syntactically valid address,
21338 the variables &$local_part$& and &$domain$& are not available during the
21339 expansion of the replacement string. The result of rewriting replaces the
21340 original address in the MAIL or RCPT command.
21343 .section "Flags controlling the rewriting process"
21344 There are four flags which control the way the rewriting process works. These
21345 take effect only when a rule is invoked, that is, when the address is of the
21346 correct type (matches the flags) and matches the pattern:
21349 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
21350 unqualified local part. It is qualified with &%qualify_recipient%&. In the
21351 absence of &"Q"& the rewritten address must always include a domain.
21353 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
21354 even if no rewriting actually takes place because of a &"fail"& in the
21355 expansion. The &"q"& flag is not effective if the address is of the wrong type
21356 (does not match the flags) or does not match the pattern.
21358 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
21359 address, up to ten times. It can be combined with the &"q"& flag, to stop
21360 rewriting once it fails to match (after at least one successful rewrite).
21362 .cindex "rewriting" "whole addresses"
21363 When an address in a header is rewritten, the rewriting normally applies only
21364 to the working part of the address, with any comments and RFC 2822 &"phrase"&
21365 left unchanged. For example, rewriting might change
21367 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
21371 From: Ford Prefect <prefectf@hitch.fict.example>
21374 Sometimes there is a need to replace the whole address item, and this can be
21375 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
21376 causes an address in a header line to be rewritten, the entire address is
21377 replaced, not just the working part. The replacement must be a complete RFC
21378 2822 address, including the angle brackets if necessary. If text outside angle
21379 brackets contains a character whose value is greater than 126 or less than 32
21380 (except for tab), the text is encoded according to RFC 2047. The character set
21381 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
21383 When the &"w"& flag is set on a rule that causes an envelope address to be
21384 rewritten, all but the working part of the replacement address is discarded.
21388 .section "Rewriting examples"
21389 Here is an example of the two common rewriting paradigms:
21391 *@*.hitch.fict.example $1@hitch.fict.example
21392 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
21393 {$value}fail}@hitch.fict.example bctfrF
21395 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
21396 the string expansion to fail if the lookup does not succeed. In this context it
21397 has the effect of leaving the original address unchanged, but Exim goes on to
21398 consider subsequent rewriting rules, if any, because the &"q"& flag is not
21399 present in that rule. An alternative to &"fail"& would be to supply &$1$&
21400 explicitly, which would cause the rewritten address to be the same as before,
21401 at the cost of a small bit of processing. Not supplying either of these is an
21402 error, since the rewritten address would then contain no local part.
21404 The first example above replaces the domain with a superior, more general
21405 domain. This may not be desirable for certain local parts. If the rule
21407 root@*.hitch.fict.example *
21409 were inserted before the first rule, rewriting would be suppressed for the
21410 local part &'root'& at any domain ending in &'hitch.fict.example'&.
21412 Rewriting can be made conditional on a number of tests, by making use of
21413 &${if$& in the expansion item. For example, to apply a rewriting rule only to
21414 messages that originate outside the local host:
21416 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
21417 {$1@hitch.fict.example}fail}"
21419 The replacement string is quoted in this example because it contains white
21422 .cindex "rewriting" "bang paths"
21423 .cindex "bang paths" "rewriting"
21424 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
21425 an address it treats it as an unqualified local part which it qualifies with
21426 the local qualification domain (if the source of the message is local or if the
21427 remote host is permitted to send unqualified addresses). Rewriting can
21428 sometimes be used to handle simple bang paths with a fixed number of
21429 components. For example, the rule
21431 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
21433 rewrites a two-component bang path &'host.name!user'& as the domain address
21434 &'user@host.name'&. However, there is a security implication in using this as
21435 a global rewriting rule for envelope addresses. It can provide a backdoor
21436 method for using your system as a relay, because the incoming addresses appear
21437 to be local. If the bang path addresses are received via SMTP, it is safer to
21438 use the &"S"& flag to rewrite them as they are received, so that relay checking
21439 can be done on the rewritten addresses.
21446 . ////////////////////////////////////////////////////////////////////////////
21447 . ////////////////////////////////////////////////////////////////////////////
21449 .chapter "Retry configuration" "CHAPretry"
21450 .scindex IIDretconf1 "retry configuration" "description of"
21451 .scindex IIDregconf2 "configuration file" "retry section"
21452 The &"retry"& section of the run time configuration file contains a list of
21453 retry rules that control how often Exim tries to deliver messages that cannot
21454 be delivered at the first attempt. If there are no retry rules, temporary
21455 errors are treated as permanent. The &%-brt%& command line option can be used
21456 to test which retry rule will be used for a given address, domain and error.
21458 The most common cause of retries is temporary failure to deliver to a remote
21459 host because the host is down, or inaccessible because of a network problem.
21460 Exim's retry processing in this case is applied on a per-host (strictly, per IP
21461 address) basis, not on a per-message basis. Thus, if one message has recently
21462 been delayed, delivery of a new message to the same host is not immediately
21463 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
21464 log selector is set, the message
21465 .cindex "retry" "time not reached"
21466 &"retry time not reached"& is written to the main log whenever a delivery is
21467 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
21468 the handling of errors during remote deliveries.
21470 Retry processing applies to routing as well as to delivering, except as covered
21471 in the next paragraph. The retry rules do not distinguish between these
21472 actions. It is not possible, for example, to specify different behaviour for
21473 failures to route the domain &'snark.fict.example'& and failures to deliver to
21474 the host &'snark.fict.example'&. I didn't think anyone would ever need this
21475 added complication, so did not implement it. However, although they share the
21476 same retry rule, the actual retry times for routing and transporting a given
21477 domain are maintained independently.
21479 When a delivery is not part of a queue run (typically an immediate delivery on
21480 receipt of a message), the routers are always run, and local deliveries are
21481 always attempted, even if retry times are set for them. This makes for better
21482 behaviour if one particular message is causing problems (for example, causing
21483 quota overflow, or provoking an error in a filter file). If such a delivery
21484 suffers a temporary failure, the retry data is updated as normal, and
21485 subsequent delivery attempts from queue runs occur only when the retry time for
21486 the local address is reached.
21490 .section "Retry rules"
21491 .cindex "retry" "rules"
21492 Each retry rule occupies one line and consists of three or four parts,
21493 separated by white space: a pattern, an error name, an optional list of sender
21494 addresses, and a list of retry parameters. The pattern and sender lists must be
21495 enclosed in double quotes if they contain white space. The rules are searched
21496 in order until one is found where the pattern, error name, and sender list (if
21497 present) match the failing host or address, the error that occurred, and the
21498 message's sender, respectively.
21501 The pattern is any single item that may appear in an address list (see section
21502 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
21503 which means that it is expanded before being tested against the address that
21504 has been delayed. Address list processing treats a plain domain name as if it
21505 were preceded by &"*@"&, which makes it possible for many retry rules to start
21506 with just a domain. For example,
21508 lookingglass.fict.example * F,24h,30m;
21510 provides a rule for any address in the &'lookingglass.fict.example'& domain,
21513 alice@lookingglass.fict.example * F,24h,30m;
21515 applies only to temporary failures involving the local part &%alice%&.
21516 In practice, almost all rules start with a domain name pattern without a local
21519 .cindex "regular expressions" "in retry rules"
21520 &*Warning*&: If you use a regular expression in a routing rule pattern, it
21521 must match a complete address, not just a domain, because that is how regular
21522 expressions work in address lists.
21524 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
21525 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
21529 .section "Choosing which retry rule to use for address errors"
21530 When Exim is looking for a retry rule after a routing attempt has failed (for
21531 example, after a DNS timeout), each line in the retry configuration is tested
21532 against the complete address only if &%retry_use_local_part%& is set for the
21533 router. Otherwise, only the domain is used, except when matching against a
21534 regular expression, when the local part of the address is replaced with &"*"&.
21535 A domain on its own can match a domain pattern, or a pattern that starts with
21536 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
21537 &%check_local_user%& is true, and false for other routers.
21539 Similarly, when Exim is looking for a retry rule after a local delivery has
21540 failed (for example, after a mailbox full error), each line in the retry
21541 configuration is tested against the complete address only if
21542 &%retry_use_local_part%& is set for the transport (it defaults true for all
21546 However, when Exim is looking for a retry rule after a remote delivery attempt
21547 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
21548 whole address is always used as the key when searching the retry rules. The
21549 rule that is found is used to create a retry time for the failing address.
21553 .section "Choosing which retry rule to use for host and message errors"
21554 For a temporary error that is not related to an individual address (for
21555 example, a connection timeout), each line in the retry configuration is checked
21556 twice. First, the name of the remote host is used as a domain name (preceded by
21557 &"*@"& when matching a regular expression). If this does not match the line,
21558 the domain from the email address is tried in a similar fashion. For example,
21559 suppose the MX records for &'a.b.c.example'& are
21561 a.b.c.example MX 5 x.y.z.example
21565 and the retry rules are
21567 p.q.r.example * F,24h,30m;
21568 a.b.c.example * F,4d,45m;
21570 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
21571 first rule matches neither the host nor the domain, so Exim looks at the second
21572 rule. This does not match the host, but it does match the domain, so it is used
21573 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
21574 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
21575 first retry rule is used, because it matches the host.
21577 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
21578 first rule to determine retry times, but for all the other hosts for the domain
21579 &'a.b.c.example'&, the second rule is used. The second rule is also used if
21580 routing to &'a.b.c.example'& suffers a temporary failure.
21582 &*Note*&: The host name is used when matching the patterns, not its IP address.
21583 However, if a message is routed directly to an IP address without the use of a
21584 host name, for example, if a &(manualroute)& router contains a setting such as:
21586 route_list = *.a.example 192.168.34.23
21588 then the &"host name"& that is used when searching for a retry rule is the
21589 textual form of the IP address.
21591 .section "Retry rules for specific errors"
21592 .cindex "retry" "specific errors; specifying"
21593 The second field in a retry rule is the name of a particular error, or an
21594 asterisk, which matches any error. The errors that can be tested for are:
21597 .vitem &%auth_failed%&
21598 Authentication failed when trying to send to a host in the
21599 &%hosts_require_auth%& list in an &(smtp)& transport.
21602 .vitem &%data_4xx%&
21603 A 4&'xx'& error was received for an outgoing DATA command, either immediately
21604 after the command, or after sending the message's data.
21606 .vitem &%mail_4xx%&
21607 A 4&'xx'& error was received for an outgoing MAIL command.
21609 .vitem &%rcpt_4xx%&
21610 A 4&'xx'& error was received for an outgoing RCPT command.
21613 For the three 4&'xx'& errors, either the first or both of the x's can be given
21614 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
21615 recognize 452 errors given to RCPT commands for addresses in a certain domain,
21616 and have retries every ten minutes with a one-hour timeout, you could set up a
21617 retry rule of this form:
21619 the.domain.name rcpt_452 F,1h,10m
21621 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
21622 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
21627 .vitem &%lost_connection%&
21628 A server unexpectedly closed the SMTP connection. There may, of course,
21629 legitimate reasons for this (host died, network died), but if it repeats a lot
21630 for the same host, it indicates something odd.
21633 .vitem &%refused_MX%&
21634 A connection to a host obtained from an MX record was refused.
21636 .vitem &%refused_A%&
21637 A connection to a host not obtained from an MX record was refused.
21640 A connection was refused.
21642 .vitem &%timeout_connect_MX%&
21643 A connection attempt to a host obtained from an MX record timed out.
21645 .vitem &%timeout_connect_A%&
21646 A connection attempt to a host not obtained from an MX record timed out.
21648 .vitem &%timeout_connect%&
21649 A connection attempt timed out.
21651 .vitem &%timeout_MX%&
21652 There was a timeout while connecting or during an SMTP session with a host
21653 obtained from an MX record.
21655 .vitem &%timeout_A%&
21656 There was a timeout while connecting or during an SMTP session with a host not
21657 obtained from an MX record.
21660 There was a timeout while connecting or during an SMTP session.
21663 .vitem &%tls_required%&
21664 The server was required to use TLS (it matched &%hosts_require_tls%& in the
21665 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
21666 to STARTTLS, or there was a problem setting up the TLS connection.
21670 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
21673 .vitem &%quota_%&<&'time'&>
21674 .cindex "quota" "error testing in retry rule"
21675 .cindex "retry" "quota error testing"
21676 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
21677 transport, and the mailbox has not been accessed for <&'time'&>. For example,
21678 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
21682 .cindex "mailbox" "time of last read"
21683 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
21684 timeouts when the mailbox is full and is not being read by its owner. Ideally,
21685 it should be based on the last time that the user accessed the mailbox.
21686 However, it is not always possible to determine this. Exim uses the following
21690 If the mailbox is a single file, the time of last access (the &"atime"&) is
21691 used. As no new messages are being delivered (because the mailbox is over
21692 quota), Exim does not access the file, so this is the time of last user access.
21694 .cindex "maildir format" "time of last read"
21695 For a maildir delivery, the time of last modification of the &_new_&
21696 subdirectory is used. As the mailbox is over quota, no new files are created in
21697 the &_new_& subdirectory, because no new messages are being delivered. Any
21698 change to the &_new_& subdirectory is therefore assumed to be the result of an
21699 MUA moving a new message to the &_cur_& directory when it is first read. The
21700 time that is used is therefore the last time that the user read a new message.
21702 For other kinds of multi-file mailbox, the time of last access cannot be
21703 obtained, so a retry rule that uses this type of error field is never matched.
21706 The quota errors apply both to system-enforced quotas and to Exim's own quota
21707 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
21708 when a local delivery is deferred because a partition is full (the ENOSPC
21713 .section "Retry rules for specified senders"
21714 .cindex "retry" "rules; sender-specific"
21715 You can specify retry rules that apply only when the failing message has a
21716 specific sender. In particular, this can be used to define retry rules that
21717 apply only to bounce messages. The third item in a retry rule can be of this
21720 &`senders=`&<&'address list'&>
21722 The retry timings themselves are then the fourth item. For example:
21724 * rcpt_4xx senders=: F,1h,30m
21727 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
21728 host. If the address list contains white space, it must be enclosed in quotes.
21731 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
21734 &*Warning*&: This facility can be unhelpful if it is used for host errors
21735 (which do not depend on the recipient). The reason is that the sender is used
21736 only to match the retry rule. Once the rule has been found for a host error,
21737 its contents are used to set a retry time for the host, and this will apply to
21738 all messages, not just those with specific senders.
21740 When testing retry rules using &%-brt%&, you can supply a sender using the
21741 &%-f%& command line option, like this:
21743 exim -f "" -brt user@dom.ain
21745 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
21746 list is never matched.
21752 .section "Retry parameters"
21753 .cindex "retry" "parameters in rules"
21754 The third (or fourth, if a senders list is present) field in a retry rule is a
21755 sequence of retry parameter sets, separated by semicolons. Each set consists of
21757 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
21759 The letter identifies the algorithm for computing a new retry time; the cutoff
21760 time is the time beyond which this algorithm no longer applies, and the
21761 arguments vary the algorithm's action. The cutoff time is measured from the
21762 time that the first failure for the domain (combined with the local part if
21763 relevant) was detected, not from the time the message was received.
21765 .cindex "retry" "algorithms"
21766 .cindex "retry" "fixed intervals"
21767 .cindex "retry" "increasing intervals"
21768 .cindex "retry" "random intervals"
21769 The available algorithms are:
21772 &'F'&: retry at fixed intervals. There is a single time parameter specifying
21775 &'G'&: retry at geometrically increasing intervals. The first argument
21776 specifies a starting value for the interval, and the second a multiplier, which
21777 is used to increase the size of the interval at each retry.
21779 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
21780 retry, the previous interval is multiplied by the factor in order to get a
21781 maximum for the next interval. The mininum interval is the first argument of
21782 the parameter, and an actual interval is chosen randomly between them. Such a
21783 rule has been found to be helpful in cluster configurations when all the
21784 members of the cluster restart at once, and may therefore synchronize their
21785 queue processing times.
21788 When computing the next retry time, the algorithm definitions are scanned in
21789 order until one whose cutoff time has not yet passed is reached. This is then
21790 used to compute a new retry time that is later than the current time. In the
21791 case of fixed interval retries, this simply means adding the interval to the
21792 current time. For geometrically increasing intervals, retry intervals are
21793 computed from the rule's parameters until one that is greater than the previous
21794 interval is found. The main configuration variable
21795 .cindex "limit" "retry interval"
21796 .cindex "retry interval" "maximum"
21797 .cindex "&%retry_interval_max%&"
21798 &%retry_interval_max%& limits the maximum interval between retries. &new("It
21799 cannot be set greater than &`24h`&, which is its default value.")
21801 A single remote domain may have a number of hosts associated with it, and each
21802 host may have more than one IP address. Retry algorithms are selected on the
21803 basis of the domain name, but are applied to each IP address independently. If,
21804 for example, a host has two IP addresses and one is unusable, Exim will
21805 generate retry times for it and will not try to use it until its next retry
21806 time comes. Thus the good IP address is likely to be tried first most of the
21809 .cindex "hints database" "use for retrying"
21810 Retry times are hints rather than promises. Exim does not make any attempt to
21811 run deliveries exactly at the computed times. Instead, a queue runner process
21812 starts delivery processes for delayed messages periodically, and these attempt
21813 new deliveries only for those addresses that have passed their next retry time.
21814 If a new message arrives for a deferred address, an immediate delivery attempt
21815 occurs only if the address has passed its retry time. In the absence of new
21816 messages, the minimum time between retries is the interval between queue runner
21817 processes. There is not much point in setting retry times of five minutes if
21818 your queue runners happen only once an hour, unless there are a significant
21819 number of incoming messages (which might be the case on a system that is
21820 sending everything to a smart host, for example).
21822 The data in the retry hints database can be inspected by using the
21823 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
21824 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
21825 &'exinext'& utility script can be used to find out what the next retry times
21826 are for the hosts associated with a particular mail domain, and also for local
21827 deliveries that have been deferred.
21830 .section "Retry rule examples"
21831 Here are some example retry rules:
21833 alice@wonderland.fict.example quota_5d F,7d,3h
21834 wonderland.fict.example quota_5d
21835 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
21836 lookingglass.fict.example * F,24h,30m;
21837 * refused_A F,2h,20m;
21838 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
21840 The first rule sets up special handling for mail to
21841 &'alice@wonderland.fict.example'& when there is an over-quota error and the
21842 mailbox has not been read for at least 5 days. Retries continue every three
21843 hours for 7 days. The second rule handles over-quota errors for all other local
21844 parts at &'wonderland.fict.example'&; the absence of a local part has the same
21845 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
21846 fail are bounced immediately if the mailbox has not been read for at least 5
21849 The third rule handles all other errors at &'wonderland.fict.example'&; retries
21850 happen every 15 minutes for an hour, then with geometrically increasing
21851 intervals until two days have passed since a delivery first failed. After the
21852 first hour there is a delay of one hour, then two hours, then four hours, and
21853 so on (this is a rather extreme example).
21855 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
21856 They happen every 30 minutes for 24 hours only. The remaining two rules handle
21857 all other domains, with special action for connection refusal from hosts that
21858 were not obtained from an MX record.
21860 The final rule in a retry configuration should always have asterisks in the
21861 first two fields so as to provide a general catch-all for any addresses that do
21862 not have their own special handling. This example tries every 15 minutes for 2
21863 hours, then with intervals starting at one hour and increasing by a factor of
21864 1.5 up to 16 hours, then every 8 hours up to 5 days.
21868 .section "Timeout of retry data"
21869 .cindex "timeout" "of retry data"
21870 .cindex "&%retry_data_expire%&"
21871 .cindex "hints database" "data expiry"
21872 .cindex "retry" "timeout of data"
21873 Exim timestamps the data that it writes to its retry hints database. When it
21874 consults the data during a delivery it ignores any that is older than the value
21875 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
21876 been tried for 7 days, Exim will try to deliver to it immediately a message
21877 arrives, and if that fails, it will calculate a retry time as if it were
21878 failing for the first time.
21880 This improves the behaviour for messages routed to rarely-used hosts such as MX
21881 backups. If such a host was down at one time, and happens to be down again when
21882 Exim tries a month later, using the old retry data would imply that it had been
21883 down all the time, which is not a justified assumption.
21885 If a host really is permanently dead, this behaviour causes a burst of retries
21886 every now and again, but only if messages routed to it are rare. It there is a
21887 message at least once every 7 days the retry data never expires.
21892 .section "Long-term failures"
21893 .cindex "delivery failure" "long-term"
21894 .cindex "retry" "after long-term failure"
21895 Special processing happens when an email address has been failing for so long
21896 that the cutoff time for the last algorithm is reached. For example, using the
21897 default retry rule:
21899 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
21901 the cutoff time is four days. Reaching the retry cutoff is independent of how
21902 long any specific message has been failing; it is the length of continuous
21903 failure for the recipient address that counts.
21905 When the cutoff time is reached for a local delivery, or for all the IP
21906 addresses associated with a remote delivery, a subsequent delivery failure
21907 causes Exim to give up on the address, and a bounce message is generated.
21908 In order to cater for new messages that use the failing address, a next retry
21909 time is still computed from the final algorithm, and is used as follows:
21911 For local deliveries, one delivery attempt is always made for any subsequent
21912 messages. If this delivery fails, the address fails immediately. The
21913 post-cutoff retry time is not used.
21915 If the delivery is remote, there are two possibilities, controlled by the
21916 .cindex "&%delay_after_cutoff%&"
21917 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
21918 default. Until the post-cutoff retry time for one of the IP addresses is
21919 reached, the failing email address is bounced immediately, without a delivery
21920 attempt taking place. After that time, one new delivery attempt is made to
21921 those IP addresses that are past their retry times, and if that still fails,
21922 the address is bounced and new retry times are computed.
21924 In other words, when all the hosts for a given email address have been failing
21925 for a long time, Exim bounces rather then defers until one of the hosts' retry
21926 times is reached. Then it tries once, and bounces if that attempt fails. This
21927 behaviour ensures that few resources are wasted in repeatedly trying to deliver
21928 to a broken destination, but if the host does recover, Exim will eventually
21931 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
21932 addresses are past their final cutoff time, Exim tries to deliver to those IP
21933 addresses that have not been tried since the message arrived. If there are
21934 no suitable IP addresses, or if they all fail, the address is bounced. In other
21935 words, it does not delay when a new message arrives, but tries the expired
21936 addresses immediately, unless they have been tried since the message arrived.
21937 If there is a continuous stream of messages for the failing domains, setting
21938 &%delay_after_cutoff%& false means that there will be many more attempts to
21939 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
21943 .section "Deliveries that work intermittently"
21944 .cindex "retry" "intermittently working deliveries"
21945 Some additional logic is needed to cope with cases where a host is
21946 intermittently available, or when a message has some attribute that prevents
21947 its delivery when others to the same address get through. In this situation,
21948 because some messages are successfully delivered, the &"retry clock"& for the
21949 host or address keeps getting restarted, and so a message could remain on the
21950 queue for ever because the cutoff time is never reached.
21952 Two exceptional actions are applied to prevent this happening. Firstly, if a
21953 message's arrival time is earlier than the &"first failed"& time for a host or
21954 address, the earlier time is used when scanning the retry rules.
21956 Secondly, if a message has been on the queue for longer than the cutoff time of
21957 any applicable retry rule for a given address, a delivery is attempted for that
21958 address, even if it is not yet time, and if this delivery fails, the address is
21959 timed out. A new retry time is not computed in this case, so that other
21960 messages for the same address are considered immediately.
21962 These two actions are probably equivalent; the fact that they both exist is a
21963 a historical accident. The second was implemented first, and was left in place
21964 when the first was added on the grounds that this was harmless, whereas
21965 removing it might have broken something in this rather tricky area.
21966 .ecindex IIDretconf1
21967 .ecindex IIDregconf2
21975 . ////////////////////////////////////////////////////////////////////////////
21976 . ////////////////////////////////////////////////////////////////////////////
21978 .chapter "SMTP authentication" "CHAPSMTPAUTH"
21979 .scindex IIDauthconf1 "SMTP" "authentication configuration"
21980 .scindex IIDauthconf2 "authentication"
21981 The &"authenticators"& section of Exim's run time configuration is concerned
21982 with SMTP authentication. This facility is an extension to the SMTP protocol,
21983 described in RFC 2554, which allows a client SMTP host to authenticate itself
21984 to a server. This is a common way for a server to recognize clients that are
21985 permitted to use it as a relay. SMTP authentication is not of relevance to the
21986 transfer of mail between servers that have no managerial connection with each
21989 .cindex "AUTH" "description of"
21990 Very briefly, the way SMTP authentication works is as follows:
21993 The server advertises a number of authentication &'mechanisms'& in response to
21994 the client's EHLO command.
21996 The client issues an AUTH command, naming a specific mechanism. The command
21997 may, optionally, contain some authentication data.
21999 The server may issue one or more &'challenges'&, to which the client must send
22000 appropriate responses. In simple authentication mechanisms, the challenges are
22001 just prompts for user names and passwords. The server does not have to issue
22002 any challenges &-- in some mechanisms the relevant data may all be transmitted
22003 with the AUTH command.
22005 The server either accepts or denies authentication.
22007 If authentication succeeds, the client may optionally make use of the AUTH
22008 option on the MAIL command to pass an authenticated sender in subsequent
22009 mail transactions. Authentication lasts for the remainder of the SMTP
22012 If authentication fails, the client may give up, or it may try a different
22013 authentication mechanism, or it may try transferring mail over the
22014 unauthenticated connection.
22017 If you are setting up a client, and want to know which authentication
22018 mechanisms the server supports, you can use Telnet to connect to port 25 (the
22019 SMTP port) on the server, and issue an EHLO command. The response to this
22020 includes the list of supported mechanisms. For example:
22022 &`$ `&&*&`telnet server.example 25`&*&
22023 &`Trying 192.168.34.25...`&
22024 &`Connected to server.example.`&
22025 &`Escape character is '^]'.`&
22026 &`220 server.example ESMTP Exim 4.20 ...`&
22027 &*&`ehlo client.example`&*&
22028 &`250-server.example Hello client.example [10.8.4.5]`&
22029 &`250-SIZE 52428800`&
22034 The second-last line of this example output shows that the server supports
22035 authentication using the PLAIN mechanism. In Exim, the different authentication
22036 mechanisms are configured by specifying &'authenticator'& drivers. Like the
22037 routers and transports, which authenticators are included in the binary is
22038 controlled by build-time definitions. The following are currently available,
22039 included by setting
22042 AUTH_CYRUS_SASL=yes
22046 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
22047 authentication mechanism (RFC 2195), and the second provides an interface to
22048 the Cyrus SASL authentication library. The third can be configured to support
22049 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
22050 not formally documented, but used by several MUAs. The fourth authenticator
22051 supports Microsoft's &'Secure Password Authentication'& mechanism.
22053 The authenticators are configured using the same syntax as other drivers (see
22054 section &<<SECTfordricon>>&). If no authenticators are required, no
22055 authentication section need be present in the configuration file. Each
22056 authenticator can in principle have both server and client functions. When Exim
22057 is receiving SMTP mail, it is acting as a server; when it is sending out
22058 messages over SMTP, it is acting as a client. Authenticator configuration
22059 options are provided for use in both these circumstances.
22061 To make it clear which options apply to which situation, the prefixes
22062 &%server_%& and &%client_%& are used on option names that are specific to
22063 either the server or the client function, respectively. Server and client
22064 functions are disabled if none of their options are set. If an authenticator is
22065 to be used for both server and client functions, a single definition, using
22066 both sets of options, is required. For example:
22070 public_name = CRAM-MD5
22071 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
22073 client_secret = secret2
22075 The &%server_%& option is used when Exim is acting as a server, and the
22076 &%client_%& options when it is acting as a client.
22078 Descriptions of the individual authenticators are given in subsequent chapters.
22079 The remainder of this chapter covers the generic options for the
22080 authenticators, followed by general discussion of the way authentication works
22085 .section "Generic options for authenticators"
22086 .cindex "authentication" "generic options"
22087 .cindex "options" "generic; for authenticators"
22090 .option driver authenticators string unset
22091 This option must always be set. It specifies which of the available
22092 authenticators is to be used.
22095 .option public_name authenticators string unset
22096 This option specifies the name of the authentication mechanism that the driver
22097 implements, and by which it is known to the outside world. These names should
22098 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
22099 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
22100 defaults to the driver's instance name.
22103 .option server_advertise_condition authenticators string&!! unset
22104 When a server is about to advertise an authentication mechanism, the condition
22105 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
22106 mechanism is not advertised.
22107 If the expansion fails, the mechanism is not advertised. If the failure was not
22108 forced, and was not caused by a lookup defer, the incident is logged.
22109 See section &<<SECTauthexiser>>& below for further discussion.
22112 .option server_debug_print authenticators string&!! unset
22113 If this option is set and authentication debugging is enabled (see the &%-d%&
22114 command line option), the string is expanded and included in the debugging
22115 output when the authenticator is run as a server. This can help with checking
22116 out the values of variables.
22117 If expansion of the string fails, the error message is written to the debugging
22118 output, and Exim carries on processing.
22121 .option server_set_id authenticators string&!! unset
22122 .cindex "&$authenticated_id$&"
22123 When an Exim server successfully authenticates a client, this string is
22124 expanded using data from the authentication, and preserved for any incoming
22125 messages in the variable &$authenticated_id$&. It is also included in the log
22126 lines for incoming messages. For example, a user/password authenticator
22127 configuration might preserve the user name that was used to authenticate, and
22128 refer to it subsequently during delivery of the message.
22129 If expansion fails, the option is ignored.
22132 .option server_mail_auth_condition authenticators string&!! unset
22133 This option allows a server to discard authenticated sender addresses supplied
22134 as part of MAIL commands in SMTP connections that are authenticated by the
22135 driver on which &%server_mail_auth_condition%& is set. The option is not used
22136 as part of the authentication process; instead its (unexpanded) value is
22137 remembered for later use.
22138 How it is used is described in the following section.
22144 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
22145 .cindex "authentication" "sender; authenticated"
22146 .cindex "AUTH" "on MAIL command"
22147 When a client supplied an AUTH= item on a MAIL command, Exim applies
22148 the following checks before accepting it as the authenticated sender of the
22152 If the connection is not using extended SMTP (that is, HELO was used rather
22153 than EHLO), the use of AUTH= is a syntax error.
22155 If the value of the AUTH= parameter is &"<>"&, it is ignored.
22157 .cindex "&$authenticated_sender$&"
22158 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
22159 running, the value of &$authenticated_sender$& is set to the value obtained
22160 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
22161 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
22162 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
22163 given for the MAIL command.
22165 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
22166 is accepted and placed in &$authenticated_sender$& only if the client has
22169 If the AUTH= value was accepted by either of the two previous rules, and
22170 the client has authenticated, and the authenticator has a setting for the
22171 &%server_mail_auth_condition%&, the condition is checked at this point. The
22172 valued that was saved from the authenticator is expanded. If the expansion
22173 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
22174 &$authenticated_sender$& is deleted. If the expansion yields any other value,
22175 the value of &$authenticated_sender$& is retained and passed on with the
22180 When &$authenticated_sender$& is set for a message, it is passed on to other
22181 hosts to which Exim authenticates as a client. Do not confuse this value with
22182 &$authenticated_id$&, which is a string obtained from the authentication
22183 process, and which is not usually a complete email address.
22185 .cindex "&$sender_address$&"
22186 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
22187 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
22188 therefore make use of &$authenticated_sender$&. The converse is not true: the
22189 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
22194 .section "Authentication on an Exim server" "SECTauthexiser"
22195 .cindex "authentication" "on an Exim server"
22196 When Exim receives an EHLO command, it advertises the public names of those
22197 authenticators that are configured as servers, subject to the following
22201 The client host must match &%auth_advertise_hosts%& (default *).
22203 It the &%server_advertise_condition%& option is set, its expansion must not
22204 yield the empty string, &"0"&, &"no"&, or &"false"&.
22207 The order in which the authenticators are defined controls the order in which
22208 the mechanisms are advertised.
22210 Some mail clients (for example, some versions of Netscape) require the user to
22211 provide a name and password for authentication whenever AUTH is advertised,
22212 even though authentication may not in fact be needed (for example, Exim may be
22213 set up to allow unconditional relaying from the client by an IP address check).
22214 You can make such clients more friendly by not advertising AUTH to them.
22215 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
22216 that runs for RCPT) to relay without authentication, you should set
22218 auth_advertise_hosts = ! 10.9.8.0/24
22220 so that no authentication mechanisms are advertised to them.
22222 The &%server_advertise_condition%& controls the advertisement of individual
22223 authentication mechanisms. For example, it can be used to restrict the
22224 advertisement of a patricular mechanism to encrypted connections, by a setting
22227 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
22229 .cindex "&$tls_cipher$&"
22230 If the session is encrypted, &$tls_cipher$& is not empty, and so the expansion
22231 yields &"yes"&, which allows the advertisement to happen.
22233 When an Exim server receives an AUTH command from a client, it rejects it
22234 immediately if AUTH was not advertised in response to an earlier EHLO
22235 command. This is the case if
22238 The client host does not match &%auth_advertise_hosts%&; or
22240 No authenticators are configured with server options; or
22242 Expansion of &%server_advertise_condition%& blocked the advertising of all the
22243 server authenticators.
22247 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
22248 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
22249 AUTH is accepted from any client host.
22251 If AUTH is not rejected by the ACL, Exim searches its configuration for a
22252 server authentication mechanism that was advertised in response to EHLO and
22253 that matches the one named in the AUTH command. If it finds one, it runs
22254 the appropriate authentication protocol, and authentication either succeeds or
22255 fails. If there is no matching advertised mechanism, the AUTH command is
22256 rejected with a 504 error.
22258 .cindex "&$received_protocol$&"
22259 .cindex "&$sender_host_authenticated$&"
22260 When a message is received from an authenticated host, the value of
22261 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
22262 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
22263 public name) of the authenticator driver that successfully authenticated the
22264 client from which the message was received. This variable is empty if there was
22265 no successful authentication.
22270 .section "Testing server authentication"
22271 .cindex "authentication" "testing a server"
22272 .cindex "AUTH" "testing a server"
22273 .cindex "base64 encoding" "creating authentication test data"
22274 Exim's &%-bh%& option can be useful for testing server authentication
22275 configurations. The data for the AUTH command has to be sent using base64
22276 encoding. A quick way to produce such data for testing is the following Perl
22280 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
22282 .cindex "binary zero" "in authentication data"
22283 This interprets its argument as a Perl string, and then encodes it. The
22284 interpretation as a Perl string allows binary zeros, which are required for
22285 some kinds of authentication, to be included in the data. For example, a
22286 command line to run this script on such data might be
22288 encode '\0user\0password'
22290 Note the use of single quotes to prevent the shell interpreting the
22291 backslashes, so that they can be interpreted by Perl to specify characters
22292 whose code value is zero.
22294 &*Warning 1*&: If either of the user or password strings starts with an octal
22295 digit, you must use three zeros instead of one after the leading backslash. If
22296 you do not, the octal digit that starts your string will be incorrectly
22297 interpreted as part of the code for the first character.
22299 &*Warning 2*&: If there are characters in the strings that Perl interprets
22300 specially, you must use a Perl escape to prevent them being misinterpreted. For
22301 example, a command such as
22303 encode '\0user@domain.com\0pas$$word'
22305 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
22307 If you have the &%mimencode%& command installed, another way to do produce
22308 base64-encoded strings is to run the command
22310 echo -e -n `\0user\0password' | mimencode
22312 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
22313 in the argument, and the &%-n%& option specifies no newline at the end of its
22314 output. However, not all versions of &%echo%& recognize these options, so you
22315 should check your version before relying on this suggestion.
22319 .section "Authentication by an Exim client"
22320 .cindex "authentication" "on an Exim client"
22321 The &(smtp)& transport has two options called &%hosts_require_auth%& and
22322 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
22323 announces support for authentication, and the host matches an entry in either
22324 of these options, Exim (as a client) tries to authenticate as follows:
22327 For each authenticator that is configured as a client, it searches the
22328 authentication mechanisms announced by the server for one whose name
22329 matches the public name of the authenticator.
22332 .cindex "&$host_address$&"
22333 When it finds one that matches, it runs the authenticator's client code.
22334 The variables &$host$& and &$host_address$& are available for any string
22335 expansions that the client might do. They are set to the server's name and
22336 IP address. If any expansion is forced to fail, the authentication attempt
22338 and Exim moves on to the next authenticator.
22339 Otherwise an expansion failure causes delivery to be
22342 If the result of the authentication attempt is a temporary error or a timeout,
22343 Exim abandons trying to send the message to the host for the moment. It will
22344 try again later. If there are any backup hosts available, they are tried in the
22347 If the response to authentication is a permanent error (5&'xx'& code), Exim
22348 carries on searching the list of authenticators and tries another one if
22349 possible. If all authentication attempts give permanent errors, or if there are
22350 no attempts because no mechanisms match (or option expansions force failure),
22351 what happens depends on whether the host matches &%hosts_require_auth%& or
22352 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
22353 delivery is deferred. The error can be detected in the retry rules, and thereby
22354 turned into a permanent error if you wish. In the second case, Exim tries to
22355 deliver the message unauthenticated.
22358 .cindex "AUTH" "on MAIL command"
22359 When Exim has authenticated itself to a remote server, it adds the AUTH
22360 parameter to the MAIL commands it sends, if it has an authenticated sender for
22361 the message. If the message came from a remote host, the authenticated sender
22362 is the one that was receiving on an incoming MAIL command, provided that the
22363 incoming connection was authenticated and the &%server_mail_auth%& condition
22364 allowed the authenticated sender to be retained. If a local process calls Exim
22365 to send a message, the sender address that is built from the login name and
22366 &%qualify_domain%& is treated as authenticated. However, if the
22367 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
22368 the authenticated sender that was received with the message.
22369 .ecindex IIDauthconf1
22370 .ecindex IIDauthconf2
22377 . ////////////////////////////////////////////////////////////////////////////
22378 . ////////////////////////////////////////////////////////////////////////////
22380 .chapter "The plaintext authenticator" "CHAPplaintext"
22381 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
22382 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
22384 The &(plaintext)& authenticator can be configured to support the PLAIN and
22385 LOGIN authentication mechanisms, both of which transfer authentication data as
22386 plain (unencrypted) text (though base64 encoded). The use of plain text is a
22387 security risk; you are strongly advised to insist on the use of SMTP encryption
22388 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
22389 use unencrypted plain text, you should not use the same passwords for SMTP
22390 connections as you do for login accounts.
22393 .section "Using plaintext in a server"
22394 .cindex "options" "&(plaintext)& authenticator (server)"
22395 When running as a server, &(plaintext)& performs the authentication test by
22396 expanding a string. It has the following options:
22398 .option server_prompts plaintext string&!! unset
22399 The contents of this option, after expansion, must be a colon-separated list of
22400 prompt strings. If expansion fails, a temporary authentication rejection is
22403 .option server_condition plaintext string&!! unset
22404 This option must be set in order to configure the driver as a server. Its use
22405 is described below.
22407 .cindex "AUTH" "in &(plaintext)& authenticator"
22408 .cindex "binary zero" "in &(plaintext)& authenticator"
22409 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
22410 "in &(plaintext)& authenticator"
22411 .cindex "&$auth1$&, &$auth2$&, etc"
22412 .cindex "base64 encoding" "in &(plaintext)& authenticator"
22414 The data sent by the client with the AUTH command, or in response to
22415 subsequent prompts, is base64 encoded, and so may contain any byte values
22416 when decoded. If any data is supplied with the command, it is treated as a
22417 list of strings, separated by NULs (binary zeros), the first three of which are
22418 placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$& (neither
22419 LOGIN nor PLAIN uses more than three strings).
22421 For compatibility with previous releases of Exim, the values are also placed in
22422 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
22423 variables for this purpose is now deprecated, as it can lead to confusion in
22424 string expansions that also use them for other things.
22427 If there are more strings in &%server_prompts%& than the number of strings
22428 supplied with the AUTH command, the remaining prompts are used to obtain more
22429 data. Each response from the client may be a list of NUL-separated strings.
22431 .cindex "&$authenticated_id$&"
22432 Once a sufficient number of data strings have been received,
22433 &%server_condition%& is expanded. If the expansion is forced to fail,
22434 authentication fails. Any other expansion failure causes a temporary error code
22435 to be returned. If the result of a successful expansion is an empty string,
22436 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
22437 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
22438 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
22439 For any other result, a temporary error code is returned, with the expanded
22440 string as the error text.
22442 &*Warning*&: If you use a lookup in the expansion to find the user's
22443 password, be sure to make the authentication fail if the user is unknown.
22444 There are good and bad examples at the end of the next section.
22448 .section "The PLAIN authentication mechanism"
22449 .cindex "PLAIN authentication mechanism"
22450 .cindex "authentication" "PLAIN mechanism"
22451 .cindex "binary zero" "in &(plaintext)& authenticator"
22452 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
22453 sent as one item of data (that is, one combined string containing two NUL
22454 separators). The data is sent either as part of the AUTH command, or
22455 subsequently in response to an empty prompt from the server.
22457 The second and third strings are a user name and a corresponding password.
22458 Using a single fixed user name and password as an example, this could be
22459 configured as follows:
22464 public_name = PLAIN
22466 server_condition = \
22467 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}\
22469 server_set_id = $auth2
22471 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
22472 the end of a string list are ignored). If all the data comes as part of the
22473 AUTH command, as is commonly the case, the prompt is not used. This
22474 authenticator is advertised in the response to EHLO as
22478 and a client host can authenticate itself by sending the command
22480 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
22482 As this contains three strings (more than the number of prompts), no further
22483 data is required from the client. Alternatively, the client may just send
22487 to initiate authentication, in which case the server replies with an empty
22488 prompt. The client must respond with the combined data string.
22490 The data string is base64 encoded, as required by the RFC. This example,
22491 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
22492 represents a zero byte. This is split up into three strings, the first of which
22493 is empty. The &%server_condition%& option in the authenticator checks that the
22494 second two are &`username`& and &`mysecret`& respectively.
22496 Having just one fixed user name and password, as in this example, is not very
22497 realistic, though for a small organization with only a handful of
22498 authenticating clients it could make sense.
22501 A more sophisticated instance of this authenticator could use the user name in
22502 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
22503 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
22504 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
22505 This is an incorrect example:
22507 server_condition = \
22508 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}{yes}{no}}
22510 The expansion uses the user name (&$auth2$&) as the key to look up a password,
22511 which it then compares to the supplied password (&$auth3$&). Why is this example
22512 incorrect? It works fine for existing users, but consider what happens if a
22513 non-existent user name is given. The lookup fails, but as no success/failure
22514 strings are given for the lookup, it yields an empty string. Thus, to defeat
22515 the authentication, all a client has to do is to supply a non-existent user
22516 name and an empty password. The correct way of writing this test is:
22518 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
22519 {${if eq{$value}{$auth3}{yes}{no}}}{no}}
22522 In this case, if the lookup succeeds, the result is checked; if the lookup
22523 fails, authentication fails. If &%crypteq%& is being used instead of &%eq%&,
22524 the first example is in fact safe, because &%crypteq%& always fails if its
22525 second argument is empty. However, the second way of writing the test makes the
22530 .section "The LOGIN authentication mechanism"
22531 .cindex "LOGIN authentication mechanism"
22532 .cindex "authentication" "LOGIN mechanism"
22533 The LOGIN authentication mechanism is not documented in any RFC, but is in use
22534 in a number of programs. No data is sent with the AUTH command. Instead, a
22535 user name and password are supplied separately, in response to prompts. The
22536 plaintext authenticator can be configured to support this as in this example:
22541 public_name = LOGIN
22542 server_prompts = User Name : Password
22543 server_condition = \
22544 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}\
22546 server_set_id = $auth1
22549 Because of the way plaintext operates, this authenticator accepts data supplied
22550 with the AUTH command (in contravention of the specification of LOGIN), but
22551 if the client does not supply it (as is the case for LOGIN clients), the prompt
22552 strings are used to obtain two data items.
22554 Some clients are very particular about the precise text of the prompts. For
22555 example, Outlook Express is reported to recognize only &"Username:"& and
22556 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
22557 strings. It uses the &%ldapauth%& expansion condition to check the user
22558 name and password by binding to an LDAP server:
22563 public_name = LOGIN
22564 server_prompts = Username:: : Password::
22565 server_condition = ${if ldapauth \
22566 {user="cn=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
22567 pass=${quote:$auth2} \
22568 ldap://ldap.example.org/}{yes}{no}}
22569 server_set_id = uid=$auth1,ou=people,o=example.org
22572 Note the use of the &%quote_ldap_dn%& operator to correctly quote the DN for
22573 authentication. However, the basic &%quote%& operator, rather than any of the
22574 LDAP quoting operators, is the correct one to use for the password, because
22575 quoting is needed only to make the password conform to the Exim syntax. At the
22576 LDAP level, the password is an uninterpreted string.
22580 .section "Support for different kinds of authentication"
22581 A number of string expansion features are provided for the purpose of
22582 interfacing to different ways of user authentication. These include checking
22583 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
22584 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
22590 .section "Using plaintext in a client"
22591 .cindex "options" "&(plaintext)& authenticator (client)"
22592 The &(plaintext)& authenticator has two client options:
22595 .option client_ignore_invalid_base64 plaintext boolean false
22596 If the client receives a server prompt that is not a valid base64 string,
22597 authentication is abandoned by default. However, if this option is set true,
22598 the error in the challenge is ignored and the client sends the response as
22602 .option client_send plaintext string&!! unset
22604 The string is a colon-separated list of authentication data strings. Each
22605 string is independently expanded before being sent to the server. The first
22606 string is sent with the AUTH command; any more strings are sent in response
22607 to prompts from the server. Before each string is expanded, the value of the
22608 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
22609 with &$auth1$& for the first prompt. Up to three prompts are stored in this
22610 way. Thus, the prompt that is received in response to sending the first string
22611 (with the AUTH command) can be used in the expansion of the second string, and
22612 so on. If an invalid base64 string is received when
22613 &%client_ignore_invalid_base64%& is set, an empty string is put in the
22614 &$auth$&<&'n'&> variable.
22617 &*Note*&: You cannot use expansion to create multiple strings, because
22618 splitting takes priority and happens first.
22620 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
22621 the data, further processing is applied to each string before it is sent. If
22622 there are any single circumflex characters in the string, they are converted to
22623 NULs. Should an actual circumflex be required as data, it must be doubled in
22626 This is an example of a client configuration that implements the PLAIN
22627 authentication mechanism with a fixed user name and password:
22631 public_name = PLAIN
22632 client_send = ^username^mysecret
22634 The lack of colons means that the entire text is sent with the AUTH
22635 command, with the circumflex characters converted to NULs. A similar example
22636 that uses the LOGIN mechanism is:
22640 public_name = LOGIN
22641 client_send = : username : mysecret
22643 The initial colon means that the first string is empty, so no data is sent with
22644 the AUTH command itself. The remaining strings are sent in response to
22646 .ecindex IIDplaiauth1
22647 .ecindex IIDplaiauth2
22652 . ////////////////////////////////////////////////////////////////////////////
22653 . ////////////////////////////////////////////////////////////////////////////
22655 .chapter "The cram_md5 authenticator"
22656 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
22657 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
22658 .cindex "CRAM-MD5 authentication mechanism"
22659 .cindex "authentication" "CRAM-MD5 mechanism"
22660 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
22661 sends a challenge string to the client, and the response consists of a user
22662 name and the CRAM-MD5 digest of the challenge string combined with a secret
22663 string (password) which is known to both server and client. Thus, the secret
22664 is not sent over the network as plain text, which makes this authenticator more
22665 secure than &(plaintext)&. However, the downside is that the secret has to be
22666 available in plain text at either end.
22669 .section "Using cram_md5 as a server"
22670 .cindex "options" "&(cram_md5)& authenticator (server)"
22671 This authenticator has one server option, which must be set to configure the
22672 authenticator as a server:
22674 .option server_secret cram_md5 string&!! unset
22675 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
22676 When the server receives the client's response, the user name is placed in
22677 the expansion variable &new("&$auth1$&"), and &%server_secret%& is expanded to
22678 obtain the password for that user. The server then computes the CRAM-MD5 digest
22679 that the client should have sent, and checks that it received the correct
22680 string. If the expansion of &%server_secret%& is forced to fail, authentication
22681 fails. If the expansion fails for some other reason, a temporary error code is
22682 returned to the client.
22685 For compatibility with previous releases of Exim, the user name is also placed
22686 in &$1$&. However, the use of this variables for this purpose is now
22687 deprecated, as it can lead to confusion in string expansions that also use
22688 numeric variables for other things.
22691 For example, the following authenticator checks that the user name given by the
22692 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
22693 user name, authentication fails.
22698 public_name = CRAM-MD5
22699 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
22700 server_set_id = $auth1
22703 .cindex "&$authenticated_id$&"
22704 If authentication succeeds, the setting of &%server_set_id%& preserves the user
22705 name in &$authenticated_id$&. A more tyical configuration might look up the
22706 secret string in a file, using the user name as the key. For example:
22711 public_name = CRAM-MD5
22712 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}{$value}fail}
22713 server_set_id = $auth1
22716 Note that this expansion explicitly forces failure if the lookup fails
22717 because &$1$& contains an unknown user name.
22720 .section "Using cram_md5 as a client"
22721 .cindex "options" "&(cram_md5)& authenticator (client)"
22722 When used as a client, the &(cram_md5)& authenticator has two options:
22726 .option client_name cram_md5 string&!! "the primary host name"
22727 This string is expanded, and the result used as the user name data when
22728 computing the response to the server's challenge.
22731 .option client_secret cram_md5 string&!! unset
22732 This option must be set for the authenticator to work as a client. Its value is
22733 expanded and the result used as the secret string when computing the response.
22737 .cindex "&$host_address$&"
22738 Different user names and secrets can be used for different servers by referring
22739 to &$host$& or &$host_address$& in the options. Forced failure of either
22740 expansion string is treated as an indication that this authenticator is not
22741 prepared to handle this case. Exim moves on to the next configured client
22742 authenticator. Any other expansion failure causes Exim to give up trying to
22743 send the message to the current server.
22745 A simple example configuration of a &(cram_md5)& authenticator, using fixed
22750 public_name = CRAM-MD5
22752 client_secret = secret
22754 .ecindex IIDcramauth1
22755 .ecindex IIDcramauth2
22759 . ////////////////////////////////////////////////////////////////////////////
22760 . ////////////////////////////////////////////////////////////////////////////
22762 .chapter "The cyrus_sasl authenticator"
22763 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
22764 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
22765 .cindex "Cyrus" "SASL library"
22766 The code for this authenticator was provided by Matthew Byng-Maddick of A L
22767 Digital Ltd (&url(http://www.aldigital.co.uk)).
22769 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
22770 library implementation of the RFC 2222 (&"Simple Authentication and Security
22771 Layer"&). This library supports a number of authentication mechanisms,
22772 including PLAIN and LOGIN, but also several others that Exim does not support
22773 directly. In particular, there is support for Kerberos authentication.
22775 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
22776 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
22777 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
22778 name of the driver to determine which mechanism to support.
22780 Where access to some kind of secret file is required, for example in GSSAPI
22781 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
22782 user, and that the Cyrus SASL library has no way of escalating privileges
22783 by default. You may also find you need to set environment variables,
22784 depending on the driver you are using.
22787 .section "Using cyrus_sasl as a server"
22789 The &(cyrus_sasl)& authenticator has four private options. It puts the username
22790 (on a successful authentication) into &$auth1$&. For compatibility with
22791 previous releases of Exim, the username is also placed in &$1$&. However, the
22792 use of this variable for this purpose is now deprecated, as it can lead to
22793 confusion in string expansions that also use numeric variables for other
22798 .option server_hostname cyrus_sasl string&!! &`$primary_hostname`&
22799 This option selects the hostname that is used when communicating with
22800 the library. It is up to the underlying SASL plug-in what it does with
22804 .option server_mech cyrus_sasl string &`public_name`&
22805 This option selects the authentication mechanism this driver should
22806 use. It allows you to use a different underlying mechanism from the
22807 advertised name. For example:
22811 driver = cyrus_sasl
22812 public_name = X-ANYTHING
22813 server_mech = CRAM-MD5
22814 server_set_id = $auth1
22818 .option server_realm cyrus_sasl string unset
22819 This specifies the SASL realm that the server claims to be in.
22822 .option server_service cyrus_sasl string &`smtp`&
22823 This is the SASL service that the server claims to implement.
22826 For straightforward cases, you do not need to set any of the authenticator's
22827 private options. All you need to do is to specify an appropriate mechanism as
22828 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
22829 PLAIN, you could have two authenticators as follows:
22833 driver = cyrus_sasl
22834 public_name = CRAM-MD5
22835 server_set_id = $auth1
22838 driver = cyrus_sasl
22839 public_name = PLAIN
22840 server_set_id = $auth1
22843 Cyrus SASL does implement the LOGIN authentication method, even though it is
22844 not a standard method. It is disabled by default in the source distribution,
22845 but it is present in many binary distributions.
22846 .ecindex IIDcyrauth1
22847 .ecindex IIDcyrauth2
22852 . ////////////////////////////////////////////////////////////////////////////
22853 . ////////////////////////////////////////////////////////////////////////////
22855 .chapter "The spa authenticator" "CHAPspa"
22856 .scindex IIDspaauth1 "&(spa)& authenticator"
22857 .scindex IIDspaauth2 "authenticators" "&(spa)&"
22858 .cindex "authentication" "Microsoft Secure Password"
22859 .cindex "authentication" "NTLM"
22860 .cindex "Microsoft Secure Password Authentication"
22861 .cindex "NTLM authentication"
22862 The &(spa)& authenticator provides client support for Microsoft's &'Secure
22863 Password Authentication'& mechanism,
22864 which is also sometimes known as NTLM (NT LanMan). The code for client side of
22865 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
22866 taken from the Samba project (&url(http://www.samba.org)). The code for the
22867 server side was subsequently contributed by Tom Kistner. The mechanism works as
22871 After the AUTH command has been accepted, the client sends an SPA
22872 authentication request based on the user name and optional domain.
22874 The server sends back a challenge.
22876 The client builds a challenge response which makes use of the user's password
22877 and sends it to the server, which then accepts or rejects it.
22880 Encryption is used to protect the password in transit.
22884 .section "Using spa as a server"
22885 .cindex "options" "&(spa)& authenticator (server)"
22886 The &(spa)& authenticator has just one server option:
22888 .option server_password spa string&!! unset
22889 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
22891 This option is expanded, and the result must be the cleartext password for the
22892 authenticating user, whose name is at this point in &$auth1$&. For
22893 compatibility with previous releases of Exim, the user name is also placed in
22894 &$1$&. However, the use of this variable for this purpose is now deprecated, as
22895 it can lead to confusion in string expansions that also use numeric variables
22896 for other things. For example:
22901 server_password = \
22902 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
22905 If the expansion is forced to fail, authentication fails. Any other expansion
22906 failure causes a temporary error code to be returned.
22912 .section "Using spa as a client"
22913 .cindex "options" "&(spa)& authenticator (client)"
22914 The &(spa)& authenticator has the following client options:
22918 .option client_domain spa string&!! unset
22919 This option specifies an optional domain for the authentication.
22922 .option client_password spa string&!! unset
22923 This option specifies the user's password, and must be set.
22926 .option client_username spa string&!! unset
22927 This option specifies the user name, and must be set. Here is an example of a
22928 configuration of this authenticator for use with the mail servers at
22934 client_username = msn/msn_username
22935 client_password = msn_plaintext_password
22936 client_domain = DOMAIN_OR_UNSET
22938 .ecindex IIDspaauth1
22939 .ecindex IIDspaauth2
22945 . ////////////////////////////////////////////////////////////////////////////
22946 . ////////////////////////////////////////////////////////////////////////////
22948 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
22949 "Encrypted SMTP connections"
22950 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
22951 .scindex IIDencsmtp2 "SMTP" "encryption"
22952 .cindex "TLS" "on SMTP connection"
22955 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
22956 Sockets Layer), is implemented by making use of the OpenSSL library or the
22957 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
22958 cryptographic code in the Exim distribution itself for implementing TLS. In
22959 order to use this feature you must install OpenSSL or GnuTLS, and then build a
22960 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
22961 You also need to understand the basic concepts of encryption at a managerial
22962 level, and in particular, the way that public keys, private keys, and
22963 certificates are used.
22965 RFC 3207 defines how SMTP connections can make use of encryption. Once a
22966 connection is established, the client issues a STARTTLS command. If the
22967 server accepts this, the client and the server negotiate an encryption
22968 mechanism. If the negotiation succeeds, the data that subsequently passes
22969 between them is encrypted.
22971 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
22972 and if so, what cipher suite is in use, whether the client supplied a
22973 certificate, and whether or not that certificate was verified. This makes it
22974 possible for an Exim server to deny or accept certain commands based on the
22977 &*Warning*&: Certain types of firewall and certain anti-virus products can
22978 disrupt TLS connections. You need to turn off SMTP scanning for these products
22979 in order to get TLS to work.
22983 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol"
22984 .cindex "ssmtp protocol"
22985 .cindex "smtps protocol"
22986 .cindex "SMTP" "ssmtp protocol"
22987 .cindex "SMTP" "smtps protocol"
22988 Early implementations of encrypted SMTP used a different TCP port from normal
22989 SMTP, and expected an encryption negotiation to start immediately, instead of
22990 waiting for a STARTTLS command from the client using the standard SMTP
22991 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
22992 allocated for this purpose.
22994 This approach was abandoned when encrypted SMTP was standardised, but there are
22995 still some legacy clients that use it. Exim supports these clients by means of
22996 the &%tls_on_connect_ports%& global option. Its value must be a list of port
22997 numbers; the most common use is expected to be:
22999 tls_on_connect_ports = 465
23001 The port numbers specified by this option apply to all SMTP connections, both
23002 via the daemon and via &'inetd'&. You still need to specify all the ports that
23003 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
23004 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
23005 an extra port &-- rather, it specifies different behaviour on a port that is
23008 There is also a &%-tls-on-connect%& command line option. This overrides
23009 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
23016 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
23017 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
23018 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
23019 followed later, when the first versions of GnuTLS were released. To build Exim
23020 to use GnuTLS, you need to set
23024 in Local/Makefile, in addition to
23028 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
23029 include files and libraries for GnuTLS can be found.
23031 There are some differences in usage when using GnuTLS instead of OpenSSL:
23034 The &%tls_verify_certificates%& option must contain the name of a file, not the
23035 name of a directory (for OpenSSL it can be either).
23037 The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no
23038 facility for varying its Diffie-Hellman parameters. I understand that this has
23039 changed, but Exim has not been updated to provide this facility.
23041 .cindex "&$tls_peerdn$&"
23042 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
23043 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
23044 affects the value of the &$tls_peerdn$& variable.
23046 OpenSSL identifies cipher suites using hyphens as separators, for example:
23047 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA_ARCFOUR_SHA. What is
23048 more, OpenSSL complains if underscores are present in a cipher list. To make
23049 life simpler, Exim changes underscores to hyhens for OpenSSL and hyphens to
23050 underscores for GnuTLS when processing lists of cipher suites in the
23051 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
23054 The &%tls_require_ciphers%& options operate differently, as described in the
23055 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
23059 .section "GnuTLS parameter computation"
23060 GnuTLS uses RSA and D-H parameters that take a substantial amount of time to
23061 compute. It is unreasonable to re-compute them for every TLS session.
23062 Therefore, Exim keeps this data in a file in its spool directory, called
23063 &_gnutls-params_&. The file is owned by the Exim user and is readable only by
23064 its owner. Every Exim process that start up GnuTLS reads the RSA and D-H
23065 parameters from this file. If the file does not exist, the first Exim process
23066 that needs it computes the data and writes it to a temporary file which is
23067 renamed once it is complete. It does not matter if several Exim processes do
23068 this simultaneously (apart from wasting a few resources). Once a file is in
23069 place, new Exim processes immediately start using it.
23071 For maximum security, the parameters that are stored in this file should be
23072 recalculated periodically, the frequency depending on your paranoia level.
23073 Arranging this is easy in principle; just delete the file when you want new
23074 values to be computed. However, there may be a problem. The calculation of new
23075 parameters needs random numbers, and these are obtained from &_/dev/random_&.
23076 If the system is not very active, &_/dev/random_& may delay returning data
23077 until enough randomness (entropy) is available. This may cause Exim to hang for
23078 a substantial amount of time, causing timeouts on incoming connections.
23080 The solution is to generate the parameters externally to Exim. They are stored
23081 in &_gnutls-params_& in PEM format, which means that they can be generated
23082 externally using the &(certtool)& command that is part of GnuTLS.
23084 To replace the parameters with new ones, instead of deleting the file
23085 and letting Exim re-create it, you can generate new parameters using
23086 &(certtool)& and, when this has been done, replace Exim's cache file by
23087 renaming. The relevant commands are something like this:
23091 # chown exim:exim new-params
23092 # chmod 0400 new-params
23093 # certtool --generate-privkey --bits 512 >new-params
23094 # echo "" >>new-params
23095 # certtool --generate-dh-params --bits 1024 >> new-params
23096 # mv new-params gnutls-params
23098 If Exim never has to generate the parameters itself, the possibility of
23099 stalling is removed.
23102 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
23103 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
23104 .cindex "&%tls_require_ciphers%&" "OpenSSL"
23105 There is a function in the OpenSSL library that can be passed a list of cipher
23106 suites before the cipher negotiation takes place. This specifies which ciphers
23107 are acceptable. The list is colon separated and may contain names like
23108 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
23109 directly to this function call. The following quotation from the OpenSSL
23110 documentation specifies what forms of item are allowed in the cipher string:
23113 It can consist of a single cipher suite such as RC4-SHA.
23115 It can represent a list of cipher suites containing a certain algorithm,
23116 or cipher suites of a certain type. For example SHA1 represents all
23117 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
23120 Lists of cipher suites can be combined in a single cipher string using
23121 the + character. This is used as a logical and operation. For example
23122 SHA1+DES represents all cipher suites containing the SHA1 and the DES
23126 Each cipher string can be optionally preceded by one of the characters &`!`&,
23129 If &`!`& is used, the ciphers are permanently deleted from the list. The
23130 ciphers deleted can never reappear in the list even if they are explicitly
23133 If &`-`& is used, the ciphers are deleted from the list, but some or all
23134 of the ciphers can be added again by later options.
23136 If &`+`& is used, the ciphers are moved to the end of the list. This
23137 option does not add any new ciphers; it just moves matching existing ones.
23140 If none of these characters is present, the string is interpreted as
23141 a list of ciphers to be appended to the current preference list. If the list
23142 includes any ciphers already present they will be ignored: that is, they will
23143 not be moved to the end of the list.
23149 .section "Requiring specific ciphers in GnuTLS" "SECTreqciphgnu"
23150 .cindex "TLS" "requiring specific ciphers (GnuTLS)"
23151 .cindex "&%tls_require_ciphers%&" "GnuTLS"
23152 The GnuTLS library does not have a combined function like OpenSSL. Instead,
23153 it allows the caller to specify separate lists of key-exchange methods,
23154 main cipher algorithms, and MAC algorithms. Unfortunately, these lists are
23155 numerical, and the library does not have a function for turning names into
23156 numbers. Consequently, the list of recognized names has to be built into
23159 At present, Exim permits only the list of main cipher algorithms to be
23160 changed. The &%tls_require_ciphers%& option is in the same format as for
23161 OpenSSL. Exim searches each item for the name of available algorithm. For
23162 example, if the list contains RSA_AES_SHA then AES is recognized.
23164 The cipher algorithms list starts out with a default set of algorithms. If
23165 the first item in &%tls_require_ciphers%& does &'not'& start with an
23166 exclamation mark, all the default items are deleted. Thus, only those specified
23167 can be used. If the first item in &%tls_require_ciphers%& &'does'& start with
23168 an exclamation mark, the defaults are left on the list.
23170 Then, any item that starts with an exclamation mark causes the relevant
23171 algorithms to be removed from the list, and any item that does not start
23172 with an exclamation mark causes the relevant algorithms to be added to the
23175 tls_require_ciphers = !RSA_ARCFOUR_SHA
23177 allows all the defaults except those that use ARCFOUR, whereas
23179 tls_require_ciphers = AES : 3DES
23181 allows only cipher suites that use AES and 3DES. The currently recognized
23182 algorithms are: AES_256, AES_128, AES (both of the preceding), 3DES, and
23183 ARCFOUR_128. Unrecognized algorithms are ignored. In a server, the order of the
23184 list is unimportant; the server will advertise the availability of all the
23185 relevant cipher suites. However, in a client, the order of the list specifies a
23186 preference order for the algorithms. The first one in the client's list that is
23187 also advertised by the server is tried first. The default order is as listed
23193 .section "Configuring an Exim server to use TLS"
23194 .cindex "TLS" "configuring an Exim server"
23195 When Exim has been built with TLS support, it advertises the availability of
23196 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
23197 but not to any others. The default value of this option is unset, which means
23198 that STARTTLS is not advertised at all. This default is chosen because you
23199 need to set some other options in order to make TLS avaliable, and also it is
23200 sensible for systems that want to use TLS only as a client.
23202 If a client issues a STARTTLS command and there is some configuration
23203 problem in the server, the command is rejected with a 454 error. If the client
23204 persists in trying to issue SMTP commands, all except QUIT are rejected
23207 554 Security failure
23209 If a STARTTLS command is issued within an existing TLS session, it is
23210 rejected with a 554 error code.
23212 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
23213 match some hosts. You can, of course, set it to * to match all hosts.
23214 However, this is not all you need to do. TLS sessions to a server won't work
23215 without some further configuration at the server end.
23217 It is rumoured that all existing clients that support TLS/SSL use RSA
23218 encryption. To make this work you need to set, in the server,
23220 tls_certificate = /some/file/name
23221 tls_privatekey = /some/file/name
23224 These options are, in fact, expanded strings, so you can make them depend on
23225 the identity of the client that is connected if you wish. The first file
23226 contains the server's X509 certificate, and the second contains the private key
23227 that goes with it. These files need to be readable by the Exim user, and must
23228 always be given as full path names. They can be the same file if both the
23229 certificate and the key are contained within it. If &%tls_privatekey%& is not
23230 set, or if its expansion is forced to fail or results in an empty string, this
23231 is assumed to be the case. The certificate file may also contain intermediate
23232 certificates that need to be sent to the client to enable it to authenticate
23233 the server's certificate.
23236 If you do not understand about certificates and keys, please try to find a
23237 source of this background information, which is not Exim-specific. (There are a
23238 few comments below in section &<<SECTcerandall>>&.)
23241 &*Note*&: These options do not apply when Exim is operating as a client &--
23242 they apply only in the case of a server. If you need to use a certificate in an
23243 Exim client, you must set the options of the same names in an &(smtp)&
23246 With just these options, an Exim server will be able to use TLS. It does not
23247 require the client to have a certificate (but see below for how to insist on
23248 this). There is one other option that may be needed in other situations. If
23251 tls_dhparam = /some/file/name
23253 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
23254 with the parameters contained in the file. This increases the set of cipher
23255 suites that the server supports. See the command
23259 for a way of generating this data. At present, &%tls_dhparam%& is used only
23260 when Exim is linked with OpenSSL. It is ignored if GnuTLS is being used.
23262 The strings supplied for these three options are expanded every time a client
23263 host connects. It is therefore possible to use different certificates and keys
23264 for different hosts, if you so wish, by making use of the client's IP address
23265 in &$sender_host_address$& to control the expansion. If a string expansion is
23266 forced to fail, Exim behaves as if the option is not set.
23268 .cindex "cipher" "logging"
23269 .cindex "log" "TLS cipher"
23270 .cindex "&$tls_cipher$&"
23271 The variable &$tls_cipher$& is set to the cipher suite that was negotiated for
23272 an incoming TLS connection. It is included in the &'Received:'& header of an
23273 incoming message (by default &-- you can, of course, change this), and it is
23274 also included in the log line that records a message's arrival, keyed by
23275 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
23276 condition can be used to test for specific cipher suites in ACLs.
23278 The ACLs that run for subsequent SMTP commands can check the name of the cipher
23279 suite and vary their actions accordingly. The cipher suite names are those used
23280 by OpenSSL. These may differ from the names used elsewhere. For example,
23281 OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts
23282 is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL
23283 documentation for more details.
23287 .section "Requesting and verifying client certificates"
23288 .cindex "certificate" "verification of client"
23289 .cindex "TLS" "client certificate verification"
23290 If you want an Exim server to request a certificate when negotiating a TLS
23291 session with a client, you must set either &%tls_verify_hosts%& or
23292 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
23293 apply to all TLS connections. For any host that matches one of these options,
23294 Exim requests a certificate as part of the setup of the TLS session. The
23295 contents of the certificate are verified by comparing it with a list of
23296 expected certificates. These must be available in a file or,
23297 for OpenSSL only (not GnuTLS), a directory, identified by
23298 &%tls_verify_certificates%&.
23300 A file can contain multiple certificates, concatenated end to end. If a
23303 each certificate must be in a separate file, with a name (or a symbolic link)
23304 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
23305 certificate. You can compute the relevant hash by running the command
23307 openssl x509 -hash -noout -in /cert/file
23309 where &_/cert/file_& contains a single certificate.
23311 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
23312 what happens if the client does not supply a certificate, or if the certificate
23313 does not match any of the certificates in the collection named by
23314 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
23315 attempt to set up a TLS session is aborted, and the incoming connection is
23316 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
23317 session continues. ACLs that run for subsequent SMTP commands can detect the
23318 fact that no certificate was verified, and vary their actions accordingly. For
23319 example, you can insist on a certificate before accepting a message for
23320 relaying, but not when the message is destined for local delivery.
23322 .cindex "&$tls_peerdn$&"
23323 When a client supplies a certificate (whether it verifies or not), the value of
23324 the Distinguished Name of the certificate is made available in the variable
23325 &$tls_peerdn$& during subsequent processing of the message.
23327 .cindex "log" "distinguished name"
23328 Because it is often a long text string, it is not included in the log line or
23329 &'Received:'& header by default. You can arrange for it to be logged, keyed by
23330 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
23331 &%received_header_text%& to change the &'Received:'& header. When no
23332 certificate is supplied, &$tls_peerdn$& is empty.
23335 .section "Revoked certificates"
23336 .cindex "TLS" "revoked certificates"
23337 .cindex "revocation list"
23338 .cindex "certificate" "revocation list"
23339 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
23340 certificates are revoked. If you have such a list, you can pass it to an Exim
23341 server using the global option called &%tls_crl%& and to an Exim client using
23342 an identically named option for the &(smtp)& transport. In each case, the value
23343 of the option is expanded and must then be the name of a file that contains a
23347 .section "Configuring an Exim client to use TLS"
23348 .cindex "cipher" "logging"
23349 .cindex "log" "TLS cipher"
23350 .cindex "log" "distinguished name"
23351 .cindex "TLS" "configuring an Exim client"
23352 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
23353 deliveries as well as to incoming, the latter one causing logging of the
23354 server certificate's DN. The remaining client configuration for TLS is all
23355 within the &(smtp)& transport.
23357 It is not necessary to set any options to have TLS work in the &(smtp)&
23358 transport. If Exim is built with TLS support, and TLS is advertised by a
23359 server, the &(smtp)& transport always tries to start a TLS session. However,
23360 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
23361 transport) to a list of server hosts for which TLS should not be used.
23363 If you do not want Exim to attempt to send messages unencrypted when an attempt
23364 to set up an encrypted connection fails in any way, you can set
23365 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
23366 those hosts, delivery is always deferred if an encrypted connection cannot be
23367 set up. If there are any other hosts for the address, they are tried in the
23370 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
23371 the message unencrypted. It always does this if the response to STARTTLS is
23372 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
23373 session after a success response code, what happens is controlled by the
23374 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
23375 delivery to this host is deferred, and other hosts (if available) are tried. If
23376 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
23377 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
23378 negotiation fails, Exim closes the current connection (because it is in an
23379 unknown state), opens a new one to the same host, and then tries the delivery
23383 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
23384 transport provide the client with a certificate, which is passed to the server
23385 if it requests it. If the server is Exim, it will request a certificate only if
23386 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. &*Note*&:
23387 These options must be set in the &(smtp)& transport for Exim to use TLS when it
23388 is operating as a client. Exim does not assume that a server certificate (set
23389 by the global options of the same name) should also be used when operating as a
23392 If &%tls_verify_certificates%& is set, it must name a file or,
23393 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
23394 expected server certificates. The client verifies the server's certificate
23395 against this collection, taking into account any revoked certificates that are
23396 in the list defined by &%tls_crl%&.
23399 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
23400 list of permitted cipher suites. If either of these checks fails, delivery to
23401 the current host is abandoned, and the &(smtp)& transport tries to deliver to
23402 alternative hosts, if any.
23405 .cindex "&$host_address$&"
23406 All the TLS options in the &(smtp)& transport are expanded before use, with
23407 &$host$& and &$host_address$& containing the name and address of the server to
23408 which the client is connected. Forced failure of an expansion causes Exim to
23409 behave as if the relevant option were unset.
23413 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
23415 .cindex "multiple SMTP deliveries with TLS"
23416 .cindex "TLS" "multiple message deliveries"
23417 Exim sends multiple messages down the same TCP/IP connection by starting up
23418 an entirely new delivery process for each message, passing the socket from
23419 one process to the next. This implementation does not fit well with the use
23420 of TLS, because there is quite a lot of state information associated with a TLS
23421 connection, not just a socket identification. Passing all the state information
23422 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
23423 session before passing the socket to a new process. The new process may then
23424 try to start a new TLS session, and if successful, may try to re-authenticate
23425 if AUTH is in use, before sending the next message.
23427 The RFC is not clear as to whether or not an SMTP session continues in clear
23428 after TLS has been shut down, or whether TLS may be restarted again later, as
23429 just described. However, if the server is Exim, this shutdown and
23430 reinitialization works. It is not known which (if any) other servers operate
23431 successfully if the client closes a TLS session and continues with unencrypted
23432 SMTP, but there are certainly some that do not work. For such servers, Exim
23433 should not pass the socket to another process, because the failure of the
23434 subsequent attempt to use it would cause Exim to record a temporary host error,
23435 and delay other deliveries to that host.
23437 To test for this case, Exim sends an EHLO command to the server after
23438 closing down the TLS session. If this fails in any way, the connection is
23439 closed instead of being passed to a new delivery process, but no retry
23440 information is recorded.
23442 There is also a manual override; you can set &%hosts_nopass_tls%& on the
23443 &(smtp)& transport to match those hosts for which Exim should not pass
23444 connections to new processes if TLS has been used.
23449 .section "Certificates and all that" "SECTcerandall"
23450 .cindex "certificate" "references to discussion"
23451 In order to understand fully how TLS works, you need to know about
23452 certificates, certificate signing, and certificate authorities. This is not the
23453 place to give a tutorial, especially as I do not know very much about it
23454 myself. Some helpful introduction can be found in the FAQ for the SSL addition
23455 to Apache, currently at
23457 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
23459 Other parts of the &'modssl'& documentation are also helpful, and have
23460 links to further files.
23461 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
23462 0-201-61598-3), contains both introductory and more in-depth descriptions.
23463 Some sample programs taken from the book are available from
23465 &url(http://www.rtfm.com/openssl-examples/)
23469 .section "Certificate chains"
23470 The file named by &%tls_certificate%& may contain more than one
23471 certificate. This is useful in the case where the certificate that is being
23472 sent is validated by an intermediate certificate which the other end does
23473 not have. Multiple certificates must be in the correct order in the file.
23474 First the host's certificate itself, then the first intermediate
23475 certificate to validate the issuer of the host certificate, then the next
23476 intermediate certificate to validate the issuer of the first intermediate
23477 certificate, and so on, until finally (optionally) the root certificate.
23478 The root certificate must already be trusted by the recipient for
23479 validation to succeed, of course, but if it's not preinstalled, sending the
23480 root certificate along with the rest makes it available for the user to
23481 install if the receiving end is a client MUA that can interact with a user.
23484 .section "Self-signed certificates"
23485 .cindex "certificate" "self-signed"
23486 You can create a self-signed certificate using the &'req'& command provided
23487 with OpenSSL, like this:
23489 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
23492 &_file1_& and &_file2_& can be the same file; the key and the certificate are
23493 delimited and so can be identified independently. The &%-days%& option
23494 specifies a period for which the certificate is valid. The &%-nodes%& option is
23495 important: if you do not set it, the key is encrypted with a passphrase
23496 that you are prompted for, and any use that is made of the key causes more
23497 prompting for the passphrase. This is not helpful if you are going to use
23498 this certificate and key in an MTA, where prompting is not possible.
23500 A self-signed certificate made in this way is sufficient for testing, and
23501 may be adequate for all your requirements if you are mainly interested in
23502 encrypting transfers, and not in secure identification.
23504 However, many clients require that the certificate presented by the server be a
23505 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
23506 certificate. In this situation, the self-signed certificate described above
23507 must be installed on the client host as a trusted root &'certification
23508 authority'& (CA), and the certificate used by Exim must be a user certificate
23509 signed with that self-signed certificate.
23511 For information on creating self-signed CA certificates and using them to sign
23512 user certificates, see the &'General implementation overview'& chapter of the
23513 Open-source PKI book, available online at
23514 &url(http://ospkibook.sourceforge.net/).
23515 .ecindex IIDencsmtp1
23516 .ecindex IIDencsmtp2
23520 . ////////////////////////////////////////////////////////////////////////////
23521 . ////////////////////////////////////////////////////////////////////////////
23523 .chapter "Access control lists" "CHAPACL"
23524 .scindex IIDacl "&ACL;" "description"
23525 .cindex "control of incoming mail"
23526 .cindex "message" "controlling incoming"
23527 .cindex "policy control" "access control lists"
23528 Access Control Lists (ACLs) are defined in a separate section of the run time
23529 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
23530 name, terminated by a colon. Here is a complete ACL section that contains just
23531 one very small ACL:
23536 accept hosts = one.host.only
23538 You can have as many lists as you like in the ACL section, and the order in
23539 which they appear does not matter. The lists are self-terminating.
23541 The majority of ACLs are used to control Exim's behaviour when it receives
23542 certain SMTP commands. This applies both to incoming TCP/IP connections, and
23543 when a local process submits a message using SMTP by specifying the &%-bs%&
23544 option. The most common use is for controlling which recipients are accepted
23545 in incoming messages. In addition, you can define an ACL that is used to check
23546 local non-SMTP messages. The default configuration file contains an example of
23547 a realistic ACL for checking RCPT commands. This is discussed in chapter
23548 &<<CHAPdefconfil>>&.
23551 .section "Testing ACLs"
23552 The &%-bh%& command line option provides a way of testing your ACL
23553 configuration locally by running a fake SMTP session with which you interact.
23554 The host &'relay-test.mail-abuse.org'& provides a service for checking your
23555 relaying configuration (see section &<<SECTcheralcon>>& for more details).
23559 .section "Specifying when ACLs are used"
23560 .cindex "&ACL;" "options for specifying"
23561 In order to cause an ACL to be used, you have to name it in one of the relevant
23562 options in the main part of the configuration. These options are:
23563 .cindex "AUTH" "ACL for"
23564 .cindex "DATA" "ACLs for"
23565 .cindex "ETRN" "ACL for"
23566 .cindex "EXPN" "ACL for"
23567 .cindex "HELO" "ACL for"
23568 .cindex "EHLO" "ACL for"
23569 .cindex "MAIL" "ACL for"
23570 .cindex "QUIT" "ACL for"
23571 .cindex "RCPT" "ACL for"
23572 .cindex "STARTTLS" "ACL for"
23573 .cindex "VRFY" "ACL for"
23574 .cindex "SMTP connection" "ACL for"
23575 .cindex "non-smtp message" "ACL for"
23578 .row &~&%acl_not_smtp%& "ACL for non-SMTP messages"
23579 .row &~&%acl_smtp_auth%& "ACL for AUTH"
23580 .row &~&%acl_smtp_connect%& "ACL for start of SMTP connection"
23581 .row &~&%acl_smtp_data%& "ACL after DATA is complete"
23582 .row &~&%acl_smtp_etrn%& "ACL for ETRN"
23583 .row &~&%acl_smtp_expn%& "ACL for EXPN"
23584 .row &~&%acl_smtp_helo%& "ACL for HELO or EHLO"
23585 .row &~&%acl_smtp_mail%& "ACL for MAIL"
23586 .row &~&%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
23587 .row &~&%acl_smtp_mime%& "ACL for content-scanning MIME parts"
23588 .row &~&%acl_smtp_predata%& "ACL at start of DATA command"
23589 .row &~&%acl_smtp_quit%& "ACL for QUIT"
23590 .row &~&%acl_smtp_rcpt%& "ACL for RCPT"
23591 .row &~&%acl_smtp_starttls%& "ACL for STARTTLS"
23592 .row &~&%acl_smtp_vrfy%& "ACL for VRFY"
23595 For example, if you set
23597 acl_smtp_rcpt = small_acl
23599 the little ACL defined above is used whenever Exim receives a RCPT command
23600 in an SMTP dialogue. The majority of policy tests on incoming messages can be
23601 done when RCPT commands arrive. A rejection of RCPT should cause the
23602 sending MTA to give up on the recipient address contained in the RCPT
23603 command, whereas rejection at other times may cause the client MTA to keep on
23604 trying to deliver the message. It is therefore recommended that you do as much
23605 testing as possible at RCPT time.
23608 .section "The non-SMTP ACL"
23609 .cindex "non-smtp message" "ACL for"
23610 The non-SMTP ACL applies to all non-interactive incoming messages, that is, it
23611 applies to batch SMTP as well as to non-SMTP messages. (Batch SMTP is not
23612 really SMTP.) This ACL is run just before the &[local_scan()]& function. Any
23613 kind of rejection is treated as permanent, because there is no way of sending a
23614 temporary error for these kinds of message. Many of the ACL conditions (for
23615 example, host tests, and tests on the state of the SMTP connection such as
23616 encryption and authentication) are not relevant and are forbidden in this ACL.
23619 .section "The connect ACL"
23620 .cindex "SMTP connection" "ACL for"
23621 The ACL test specified by &%acl_smtp_connect%& happens after the test specified
23622 by &%host_reject_connection%& (which is now an anomaly) and any TCP Wrappers
23623 testing (if configured).
23626 .section "The DATA ACLs"
23627 .cindex "DATA" "ACLs for"
23628 Two ACLs are associated with the DATA command, because it is two-stage
23629 command, with two responses being sent to the client.
23630 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
23631 is obeyed. This gives you control after all the RCPT commands, but before
23632 the message itself is received. It offers the opportunity to give a negative
23633 response to the DATA command before the data is transmitted. Header lines
23634 added by MAIL or RCPT ACLs are not visible at this time, but any that
23635 are defined here are visible when the &%acl_smtp_data%& ACL is run.
23637 You cannot test the contents of the message, for example, to verify addresses
23638 in the headers, at RCPT time or when the DATA command is received. Such
23639 tests have to appear in the ACL that is run after the message itself has been
23640 received, before the final response to the DATA command is sent. This is
23641 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
23642 associated with the DATA command.
23644 For both of these ACLs, it is not possible to reject individual recipients. An
23645 error response rejects the entire message. Unfortunately, it is known that some
23646 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
23647 before or after the data) correctly &-- they keep the message on their queues
23648 and try again later, but that is their problem, though it does waste some of
23652 .section "The MIME ACL"
23653 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
23654 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
23657 .section "The QUIT ACL" "SECTQUITACL"
23658 .cindex "QUIT" "ACL for"
23659 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
23660 does not affect the response code to QUIT, which is always 221. Thus, the ACL
23661 does not in fact control any access. For this reason, the only verbs that are
23662 permitted are &%accept%& and &%warn%&.
23664 This ACL can be used for tasks such as custom logging at the end of an SMTP
23665 session. For example, you can use ACL variables in other ACLs to count
23666 messages, recipients, etc., and log the totals at QUIT time using one or
23667 more &%logwrite%& modifiers on a &%warn%& verb.
23669 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
23670 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
23672 You do not need to have a final &%accept%&, but if you do, you can use a
23673 &%message%& modifier to specify custom text that is sent as part of the 221
23676 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
23677 failure (for example, failure to open a log file, or when Exim is bombing out
23678 because it has detected an unrecoverable error), all SMTP commands from the
23679 client are given temporary error responses until QUIT is received or the
23680 connection is closed. In these special cases, the QUIT ACL does not run.
23684 .section "Finding an ACL to use"
23685 .cindex "&ACL;" "finding which to use"
23686 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so you can
23687 use different ACLs in different circumstances. The resulting string does not
23688 have to be the name of an ACL in the configuration file; there are other
23689 possibilities. Having expanded the string, Exim searches for an ACL as follows:
23692 If the string begins with a slash, Exim uses it as a file name, and reads its
23693 contents as an ACL. The lines are processed in the same way as lines in the
23694 Exim configuration file. In particular, continuation lines are supported, blank
23695 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
23696 If the file does not exist or cannot be read, an error occurs (typically
23697 causing a temporary failure of whatever caused the ACL to be run). For example:
23699 acl_smtp_data = /etc/acls/\
23700 ${lookup{$sender_host_address}lsearch\
23701 {/etc/acllist}{$value}{default}}
23703 This looks up an ACL file to use on the basis of the host's IP address, falling
23704 back to a default if the lookup fails. If an ACL is successfully read from a
23705 file, it is retained in memory for the duration of the Exim process, so that it
23706 can be re-used without having to re-read the file.
23708 If the string does not start with a slash, and does not contain any spaces,
23709 Exim searches the ACL section of the configuration for an ACL whose name
23710 matches the string.
23712 If no named ACL is found, or if the string contains spaces, Exim parses
23713 the string as an inline ACL. This can save typing in cases where you just
23714 want to have something like
23716 acl_smtp_vrfy = accept
23718 in order to allow free use of the VRFY command. Such a string may contain
23719 newlines; it is processed in the same way as an ACL that is read from a file.
23725 .section "ACL return codes"
23726 .cindex "&ACL;" "return codes"
23727 Except for the QUIT ACL, which does not affect the SMTP return code (see
23728 section &<<SECTQUITACL>>& above), the result of running an ACL is either
23729 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
23730 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
23731 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
23732 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
23733 This also causes a 4&'xx'& return code.
23735 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
23736 &"deny"&, because there is no mechanism for passing temporary errors to the
23737 submitters of non-SMTP messages.
23740 ACLs that are relevant to message reception may also return &"discard"&. This
23741 has the effect of &"accept"&, but causes either the entire message or an
23742 individual recipient address to be discarded. In other words, it is a
23743 blackholing facility. Use it with care.
23745 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
23746 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
23747 RCPT ACL is to discard just the one recipient address. If there are no
23748 recipients left when the message's data is received, the DATA ACL is not
23749 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
23750 remaining recipients. The &"discard"& return is not permitted for the
23751 &%acl_smtp_predata%& ACL.
23754 .cindex "&[local_scan()]& function" "when all recipients discarded"
23755 The &[local_scan()]& function is always run, even if there are no remaining
23756 recipients; it may create new recipients.
23760 .section "Unset ACL options"
23761 .cindex "&ACL;" "unset options"
23762 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
23763 all the same. &*Note*&: These defaults apply only when the relevant ACL is
23764 not defined at all. For any defined ACL, the default action when control
23765 reaches the end of the ACL statements is &"deny"&.
23767 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
23768 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
23769 &%acl_smtp_mime%&, &%acl_smtp_predata%&, &%acl_smtp_quit%&, and
23770 &%acl_smtp_starttls%&, the action when the ACL is not defined is &"accept"&.
23772 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
23773 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
23774 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
23775 messages over an SMTP connection. For an example, see the ACL in the default
23776 configuration file.
23781 .section "Data for message ACLs"
23782 .cindex "&ACL;" "data for message ACL"
23784 .cindex &$local_part$&
23785 .cindex &$sender_address$&
23786 .cindex &$sender_host_address$&
23787 .cindex &$smtp_command$&
23788 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
23789 that contain information about the host and the message's sender (for example,
23790 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
23791 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
23792 &$local_part$& are set from the argument address. The entire SMTP command
23793 is available in &$smtp_command$&.
23795 When an ACL for the AUTH parameter of MAIL is running, the variables that
23796 contain information about the host are set, but &$sender_address$& is not yet
23797 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
23800 .cindex "&$message_size$&"
23801 The &$message_size$& variable is set to the value of the SIZE parameter on
23802 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
23803 that parameter is not given. The value is updated to the true message size by
23804 the time the final DATA ACL is run (after the message data has been
23807 .cindex "&$rcpt_count$&"
23808 .cindex "&$recipients_count$&"
23809 The &$rcpt_count$& variable increases by one for each RCPT command received.
23810 The &$recipients_count$& variable increases by one each time a RCPT command is
23811 accepted, so while an ACL for RCPT is being processed, it contains the number
23812 of previously accepted recipients. At DATA time (for both the DATA ACLs),
23813 &$rcpt_count$& contains the total number of RCPT commands, and
23814 &$recipients_count$& contains the total number of accepted recipients.
23820 .section "Data for non-message ACLs" "SECTdatfornon"
23821 .cindex "&ACL;" "data for non-message ACL"
23822 .cindex &$smtp_command_argument$&
23823 .cindex &$smtp_command$&
23824 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
23825 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
23826 and the entire SMTP command is available in &$smtp_command$&.
23827 These variables can be tested using a &%condition%& condition. For example,
23828 here is an ACL for use with AUTH, which insists that either the session is
23829 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
23830 does not permit authentication methods that use cleartext passwords on
23831 unencrypted connections.
23834 accept encrypted = *
23835 accept condition = ${if eq{${uc:$smtp_command_argument}}\
23837 deny message = TLS encryption or CRAM-MD5 required
23839 (Another way of applying this restriction is to arrange for the authenticators
23840 that use cleartext passwords not to be advertised when the connection is not
23841 encrypted. You can use the generic &%server_advertise_condition%& authenticator
23842 option to do this.)
23846 .section "Format of an ACL"
23847 .cindex "&ACL;" "format of"
23848 .cindex "&ACL;" "verbs; definition of"
23849 An individual ACL consists of a number of statements. Each statement starts
23850 with a verb, optionally followed by a number of conditions and &"modifiers"&.
23851 Modifiers can change the way the verb operates, define error and log messages,
23852 set variables, insert delays, and vary the processing of accepted messages.
23854 If all the conditions are met, the verb is obeyed. The same condition may be
23855 used (with different arguments) more than once in the same statement. This
23856 provides a means of specifying an &"and"& conjunction between conditions. For
23859 deny dnslists = list1.example
23860 dnslists = list2.example
23862 If there are no conditions, the verb is always obeyed. Exim stops evaluating
23863 the conditions and modifiers when it reaches a condition that fails. What
23864 happens then depends on the verb (and in one case, on a special modifier). Not
23865 all the conditions make sense at every testing point. For example, you cannot
23866 test a sender address in the ACL that is run for a VRFY command.
23869 .section "ACL verbs"
23870 The ACL verbs are as follows:
23873 .cindex "&%accept%&" "ACL verb"
23874 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
23875 of the conditions are not met, what happens depends on whether &%endpass%&
23876 appears among the conditions (for syntax see below). If the failing condition
23877 is before &%endpass%&, control is passed to the next ACL statement; if it is
23878 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
23879 check a RCPT command:
23881 accept domains = +local_domains
23885 If the recipient domain does not match the &%domains%& condition, control
23886 passes to the next statement. If it does match, the recipient is verified, and
23887 the command is accepted if verification succeeds. However, if verification
23888 fails, the ACL yields &"deny"&, because the failing condition is after
23892 .cindex "&%defer%&" "ACL verb"
23893 &%defer%&: If all the conditions are met, the ACL returns &"defer"& which, in
23894 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
23895 &%defer%& is the same as &%deny%&, because there is no way of sending a
23896 temporary error. For a RCPT command, &%defer%& is much the same as using a
23897 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
23898 be used in any ACL, and even for a recipient it might be a simpler approach.
23900 .cindex "&%deny%&" "ACL verb"
23901 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
23902 the conditions are not met, control is passed to the next ACL statement. For
23905 deny dnslists = blackholes.mail-abuse.org
23907 rejects commands from hosts that are on a DNS black list.
23910 .cindex "&%discard%&" "ACL verb"
23911 &%discard%&: This verb behaves like &%accept%&, except that it returns
23912 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
23913 that are concerned with receiving messages, and it causes recipients to be
23914 discarded. If the &%log_message%& modifier is set when &%discard%& operates,
23915 its contents are added to the line that is automatically written to the log.
23917 If &%discard%& is used in an ACL for RCPT, just the one recipient is
23918 discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
23919 message's recipients are discarded. Recipients that are discarded before
23920 DATA do not appear in the log line when the &%log_recipients%& log selector
23923 .cindex "&%drop%&" "ACL verb"
23924 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
23925 forcibly closed after the 5&'xx'& error message has been sent. For example:
23927 drop message = I don't take more than 20 RCPTs
23928 condition = ${if > {$rcpt_count}{20}}
23930 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
23931 The connection is always dropped after sending a 550 response.
23934 .cindex "&%require%&" "ACL verb"
23935 &%require%&: If all the conditions are met, control is passed to the next ACL
23936 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
23937 example, when checking a RCPT command,
23939 require verify = sender
23941 passes control to subsequent statements only if the message's sender can be
23942 verified. Otherwise, it rejects the command.
23945 .cindex "&%warn%&" "ACL verb"
23946 &%warn%&: If all the conditions are met, a header line is added to an incoming
23947 message and/or a line is written to Exim's main log. In all cases, control
23948 passes to the next ACL statement. The text of the added header line and the log
23949 line are specified by modifiers; if they are not present, a &%warn%& verb just
23950 checks its conditions and obeys any &"immediate"& modifiers such as &%set%& and
23951 &%logwrite%&. There is more about adding header lines in section
23952 &<<SECTaddheadacl>>&.
23954 If any condition on a &%warn%& statement cannot be completed (that is, there is
23955 some sort of defer), no header lines are added and the configured log line is
23956 not written. No further conditions or modifiers in the &%warn%& statement are
23957 processed. The incident is logged, but the ACL continues to be processed, from
23958 the next statement onwards.
23960 If a &%message%& modifier is present on a &%warn%& verb in an ACL that is not
23961 testing an incoming message, it is ignored, and the incident is logged.
23963 A &%warn%& statement may use the &%log_message%& modifier to cause a line to be
23964 written to the main log when the statement's conditions are true.
23965 If an identical log line is requested several times in the same message, only
23966 one copy is actually written to the log. If you want to force duplicates to be
23967 written, use the &%logwrite%& modifier instead.
23969 .cindex "&$acl_verify_message$&"
23970 When one of the &%warn%& conditions is an address verification that fails, the
23971 text of the verification failure message is in &$acl_verify_message$&. If you
23972 want this logged, you must set it up explicitly. For example:
23974 warn !verify = sender
23975 log_message = sender verify failed: $acl_verify_message
23979 At the end of each ACL there is an implicit unconditional &%deny%&.
23981 As you can see from the examples above, the conditions and modifiers are
23982 written one to a line, with the first one on the same line as the verb, and
23983 subsequent ones on following lines. If you have a very long condition, you can
23984 continue it onto several physical lines by the usual backslash continuation
23985 mechanism. It is conventional to align the conditions vertically.
23989 .section "ACL variables" "SECTaclvariables"
23990 .cindex "&ACL;" "variables"
23991 There are some special variables that can be set during ACL processing. They
23992 can be used to pass information between different ACLs, different invocations
23993 of the same ACL in the same SMTP connection, and between ACLs and the routers,
23994 transports, and filters that are used to deliver a message. There are two sets
23995 of these variables:
23998 The values of &$acl_c0$& to &new(&$acl_c19$&) persist throughout an SMTP
23999 connection. They are never reset. Thus, a value that is set while receiving one
24000 message is still available when receiving the next message on the same SMTP
24003 The values of &$acl_m0$& to &new(&$acl_m19$&) persist only while a message is
24004 being received. They are reset afterwards. They are also reset by MAIL, RSET,
24005 EHLO, HELO, and after starting up a TLS session.
24008 When a message is accepted, the current values of all the ACL variables are
24009 preserved with the message and are subsequently made available at delivery
24010 time. The ACL variables are set by modifier called &%set%&. For example:
24012 accept hosts = whatever
24013 set acl_m4 = some value
24015 &*Note*&: A leading dollar sign is not used when naming a variable that is to
24016 be set. If you want to set a variable without taking any action, you can use a
24017 &%warn%& verb without any other modifiers or conditions.
24021 .section "Condition and modifier processing"
24022 .cindex "&ACL;" "conditions; processing"
24023 .cindex "&ACL;" "modifiers; processing"
24024 An exclamation mark preceding a condition negates its result. For example:
24026 deny domains = *.dom.example
24027 !verify = recipient
24029 causes the ACL to return &"deny"& if the recipient domain ends in
24030 &'dom.example'& and the recipient address cannot be verified. Sometimes
24031 negation can be used on the right-hand side of a condition. For example, these
24032 two statements are equivalent:
24034 deny hosts = !192.168.3.4
24035 deny !hosts = 192.168.3.4
24037 However, for many conditions (&%verify%& being a good example), only left-hand
24038 side negation of the whole condition is possible.
24040 The arguments of conditions and modifiers are expanded. A forced failure
24041 of an expansion causes a condition to be ignored, that is, it behaves as if the
24042 condition is true. Consider these two statements:
24044 accept senders = ${lookup{$host_name}lsearch\
24045 {/some/file}{$value}fail}
24046 accept senders = ${lookup{$host_name}lsearch\
24047 {/some/file}{$value}{}}
24049 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
24050 the returned list is searched, but if the lookup fails the behaviour is
24051 different in the two cases. The &%fail%& in the first statement causes the
24052 condition to be ignored, leaving no further conditions. The &%accept%& verb
24053 therefore succeeds. The second statement, however, generates an empty list when
24054 the lookup fails. No sender can match an empty list, so the condition fails,
24055 and therefore the &%accept%& also fails.
24057 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
24058 specify actions that are taken as the conditions for a statement are checked;
24059 others specify text for messages that are used when access is denied or a
24060 warning is generated. The &%control%& modifier affects the way an incoming
24061 message is handled.
24063 The positioning of the modifiers in an ACL statement important, because the
24064 processing of a verb ceases as soon as its outcome is known. Only those
24065 modifiers that have already been encountered will take effect. For example,
24066 consider this use of the &%message%& modifier:
24068 require message = Can't verify sender
24070 message = Can't verify recipient
24072 message = This message cannot be used
24074 If sender verification fails, Exim knows that the result of the statement is
24075 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
24076 so its text is used as the error message. If sender verification succeeds, but
24077 recipient verification fails, the second message is used. If recipient
24078 verification succeeds, the third message becomes &"current"&, but is never used
24079 because there are no more conditions to cause failure.
24081 For the &%deny%& verb, on the other hand, it is always the last &%message%&
24082 modifier that is used, because all the conditions must be true for rejection to
24083 happen. Specifying more than one &%message%& modifier does not make sense, and
24084 the message can even be specified after all the conditions. For example:
24087 !senders = *@my.domain.example
24088 message = Invalid sender from client host
24090 The &"deny"& result does not happen until the end of the statement is reached,
24091 by which time Exim has set up the message.
24095 .section "ACL modifiers" "SECTACLmodi"
24096 .cindex "&ACL;" "modifiers; list of"
24097 The ACL modifiers are as follows:
24101 .vitem &*add_header*&&~=&~<&'text'&>
24102 This modifier specifies one of more header lines that are to be added to an
24103 incoming message, assuming, of course, that the message is ultimately
24104 accepted. For details, see section &<<SECTaddheadacl>>&.
24107 .vitem &*control*&&~=&~<&'text'&>
24108 .cindex "&%control%&" "ACL modifier"
24109 This modifier affects the subsequent processing of the SMTP connection or of an
24110 incoming message that is accepted. The effect of the first type of control
24111 lasts for the duration of the connection, whereas the effect of the second type
24112 lasts only until the current message has been received. The message-specific
24113 controls always apply to the whole message, not to individual recipients,
24114 even if the &%control%& modifier appears in a RCPT ACL.
24116 As there are now quite a few controls that can be applied, they are described
24117 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
24118 in several different ways. For example:
24120 . ==== As this is a nested list, any displays it contains must be indented
24121 . ==== as otherwise they are too far to the left.
24124 It can be at the end of an &%accept%& statement:
24126 accept ...some conditions
24127 control = queue_only
24129 In this case, the control is applied when this statement yields &"accept"&, in
24130 other words, when the conditions are all true.
24133 It can be in the middle of an &%accept%& statement:
24135 accept ...some conditions...
24136 control = queue_only
24137 ...some more conditions...
24139 If the first set of conditions are true, the control is applied, even if the
24140 statement does not accept because one of the second set of conditions is false.
24141 In this case, some subsequent statement must yield &"accept"& for the control
24145 It can be used with &%warn%& to apply the control, leaving the
24146 decision about accepting or denying to a subsequent verb. For
24149 warn ...some conditions...
24153 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
24154 &%logwrite%&, so it does not add anything to the message and does not write a
24158 If you want to apply a control unconditionally, you can use it with a
24159 &%require%& verb. For example:
24161 require control = no_multiline_response
24165 .vitem &*delay*&&~=&~<&'time'&>
24166 .cindex "&%delay%&" "ACL modifier"
24167 .cindex "&%-bh%& option"
24168 This modifier causes Exim to wait for the time interval before proceeding. The
24169 time is given in the usual Exim notation. This modifier may appear in any ACL.
24170 The delay happens as soon as the modifier is processed. However, when testing
24171 Exim using the &%-bh%& option, the delay is not actually imposed (an
24172 appropriate message is output instead).
24174 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
24177 deny ...some conditions...
24180 The delay happens if all the conditions are true, before the statement returns
24181 &"deny"&. Compare this with:
24184 ...some conditions...
24186 which waits for 30s before processing the conditions. The &%delay%& modifier
24187 can also be used with &%warn%& and together with &%control%&:
24189 warn ...some conditions...
24196 .cindex "&%endpass%&" "ACL modifier"
24197 This modifier, which has no argument, is recognized only in &%accept%&
24198 statements. It marks the boundary between the conditions whose failure causes
24199 control to pass to the next statement, and the conditions whose failure causes
24200 the ACL to return &"deny"&. See the description of &%accept%& above.
24202 .vitem &*log_message*&&~=&~<&'text'&>
24203 .cindex "&%log_message%&" "ACL modifier"
24204 This modifier sets up a message that is used as part of the log message if the
24205 ACL denies access or a &%warn%& statement's conditions are true. For example:
24207 require log_message = wrong cipher suite $tls_cipher
24208 encrypted = DES-CBC3-SHA
24210 &%log_message%& adds to any underlying error message that may exist because of
24211 the condition failure. For example, while verifying a recipient address, a
24212 &':fail:'& redirection might have already set up a message. Although the
24213 message is usually defined before the conditions to which it applies, the
24214 expansion does not happen until Exim decides that access is to be denied. This
24215 means that any variables that are set by the condition are available for
24216 inclusion in the message. For example, the &$dnslist_$&<&'xxx'&> variables are
24217 set after a DNS black list lookup succeeds. If the expansion of &%log_message%&
24218 fails, or if the result is an empty string, the modifier is ignored.
24220 .cindex "&$acl_verify_message$&"
24221 If you want to use a &%warn%& statement to log the result of an address
24222 verification, you can use &$acl_verify_message$& to include the verification
24225 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
24226 the start of the logged message. If the same warning log message is requested
24227 more than once while receiving a single email message, only one copy is
24228 actually logged. If you want to log multiple copies, use &%logwrite%& instead
24229 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
24230 is logged for a succesful &%warn%& statement.
24232 If &%log_message%& is not present and there is no underlying error message (for
24233 example, from the failure of address verification), but &%message%& is present,
24234 the &%message%& text is used for logging rejections. However, if any text for
24235 logging contains newlines, only the first line is logged. In the absence of
24236 both &%log_message%& and &%message%&, a default built-in message is used for
24237 logging rejections.
24239 .vitem &*logwrite*&&~=&~<&'text'&>
24240 .cindex "&%logwrite%&" "ACL modifier"
24241 .cindex "logging in ACL" "immediate"
24242 This modifier writes a message to a log file as soon as it is encountered when
24243 processing an ACL. (Compare &%log_message%&, which, except in the case of
24244 &%warn%&, is used only if the ACL statement denies access.) The &%logwrite%&
24245 modifier can be used to log special incidents in ACLs. For example:
24247 &`accept `&<&'some special conditions'&>
24248 &` control = freeze`&
24249 &` logwrite = froze message because ...`&
24251 By default, the message is written to the main log. However, it may begin
24252 with a colon, followed by a comma-separated list of log names, and then
24253 another colon, to specify exactly which logs are to be written. For
24256 logwrite = :main,reject: text for main and reject logs
24257 logwrite = :panic: text for panic log only
24260 .vitem &*message*&&~=&~<&'text'&>
24261 .cindex "&%message%&" "ACL modifier"
24262 This modifier sets up a text string that is expanded and used as an error
24263 message if the current statement causes the ACL to deny access. The expansion
24264 happens at the time Exim decides that access is to be denied, not at the time
24265 it processes &%message%&. If the expansion fails, or generates an empty string,
24266 the modifier is ignored. For ACLs that are triggered by SMTP commands, the
24267 message is returned as part of the SMTP error response.
24269 The text is literal; any quotes are taken as literals, but because the string
24270 is expanded, backslash escapes are processed anyway. If the message contains
24271 newlines, this gives rise to a multi-line SMTP response. Like &%log_message%&,
24272 the contents of &%message%& are not expanded until after a condition has
24275 .cindex "&$acl_verify_message$&"
24276 If &%message%& is used on a statement that verifies an address, the message
24277 specified overrides any message that is generated by the verification process.
24278 However, the original message is available in the variable
24279 &$acl_verify_message$&, so you can incorporate it into your message if you
24280 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
24281 routers to be passed back as part of the SMTP response, you should either not
24282 use a &%message%& modifier, or make use of &$acl_verify_message$&.
24285 For compatibility with previous releases of Exim, a &%message%& modifier that
24286 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
24287 modifier, but this usage is now deprecated. However, &%message%& acts only when
24288 all the conditions are true, wherever it appears in an ACL command, whereas
24289 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
24290 &%warn%& in an ACL that is not concerned with receiving a message, it has no
24294 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
24295 .cindex "&%set%&" "ACL modifier"
24296 This modifier puts a value into one of the ACL variables (see section
24297 &<<SECTaclvariables>>&).
24304 .section "Use of the control modifier" "SECTcontrols"
24305 .cindex "&%control%&" "ACL modifier"
24306 The &%control%& modifier supports the following settings:
24310 .vitem &*control&~=&~allow_auth_unadvertised*&
24311 This modifier allows a client host to use the SMTP AUTH command even when it
24312 has not been advertised in response to EHLO. Furthermore, because there are
24313 apparently some really broken clients that do this, Exim will accept AUTH after
24314 HELO (rather than EHLO) when this control is set. It should be used only if you
24315 really need it, and you should limit its use to those broken clients that do
24316 not work without it. For example:
24318 warn hosts = 192.168.34.25
24319 control = allow_auth_unadvertised
24321 Normally, when an Exim server receives an AUTH command, it checks the name of
24322 the authentication mechanism that is given in the command to ensure that it
24323 matches an advertised mechanism. When this control is set, the check that a
24324 mechanism has been advertised is bypassed. Any configured mechanism can be used
24325 by the client. This control is permitted only in the connection and HELO ACLs.
24329 .vitem &*control&~=&~caseful_local_part*&
24332 .vitem &*control&~=&~caselower_local_part*&
24333 .cindex "&ACL;" "case of local part in"
24334 .cindex "case of local parts"
24335 .cindex "&$local_part$&"
24336 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
24337 (that is, during RCPT processing). By default, the contents of &$local_part$&
24338 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
24339 any uppercase letters in the original local part are restored in &$local_part$&
24340 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
24343 These controls affect only the current recipient. Moreover, they apply only to
24344 local part handling that takes place directly in the ACL (for example, as a key
24345 in lookups). If a test to verify the recipient is obeyed, the case-related
24346 handling of the local part during the verification is controlled by the router
24347 configuration (see the &%caseful_local_part%& generic router option).
24349 This facility could be used, for example, to add a spam score to local parts
24350 containing upper case letters. For example, using &$acl_m4$& to accumulate the
24353 warn control = caseful_local_part
24354 set acl_m4 = ${eval:\
24356 ${if match{$local_part}{[A-Z]}{1}{0}}\
24358 control = caselower_local_part
24360 Notice that we put back the lower cased version afterwards, assuming that
24361 is what is wanted for subsequent tests.
24363 .vitem &*control&~=&~enforce_sync*&
24366 .vitem &*control&~=&~no_enforce_sync*&
24367 .cindex "SMTP" "synchronization checking"
24368 .cindex "synchronization checking in SMTP"
24369 These controls make it possible to be selective about when SMTP synchronization
24370 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
24371 state of the switch (it is true by default). See the description of this option
24372 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
24374 The effect of these two controls lasts for the remainder of the SMTP
24375 connection. They can appear in any ACL except the one for the non-SMTP
24376 messages. The most straightforward place to put them is in the ACL defined by
24377 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
24378 before the first synchronization check. The expected use is to turn off the
24379 synchronization checks for badly-behaved hosts that you nevertheless need to
24383 .vitem &*control&~=&~fakedefer/*&<&'message'&>
24384 .cindex "fake defer"
24385 .cindex "defer" "fake"
24386 This control works in exactly the same way as &%fakereject%& (described below)
24387 except that it causes an SMTP 450 response after the message data instead of a
24388 550 response. You must take care when using &%fakedefer%& because it causes the
24389 messages to be duplicated when the sender retries. Therefore, you should not
24390 use &%fakedefer%& if the message is to be delivered normally.
24392 .vitem &*control&~=&~fakereject/*&<&'message'&>
24393 .cindex "fake rejection"
24394 .cindex "rejection" "fake"
24395 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
24396 words, only when an SMTP message is being received. If Exim accepts the
24397 message, instead the final 250 response, a 550 rejection message is sent.
24398 However, Exim proceeds to deliver the message as normal. The control applies
24399 only to the current message, not to any subsequent ones that may be received in
24400 the same SMTP connection.
24402 The text for the 550 response is taken from the &%control%& modifier. If no
24403 message is supplied, the following is used:
24405 550-Your message has been rejected but is being
24406 550-kept for evaluation.
24407 550-If it was a legitimate message, it may still be
24408 550 delivered to the target recipient(s).
24410 This facilty should be used with extreme caution.
24412 .vitem &*control&~=&~freeze*&
24413 .cindex "frozen messages" "forcing in ACL"
24414 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
24415 other words, only when a message is being received. If the message is accepted,
24416 it is placed on Exim's queue and frozen. The control applies only to the
24417 current message, not to any subsequent ones that may be received in the same
24421 This modifier can optionally be followed by &`/no_tell`&. If the global option
24422 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
24423 is told about the freezing), provided all the &*control=freeze*& modifiers that
24424 are obeyed for the current message have the &`/no_tell`& option.
24428 .vitem &*control&~=&~no_mbox_unspool*&
24429 This control is available when Exim is compiled with the content scanning
24430 extension. Content scanning may require a copy of the current message, or parts
24431 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
24432 or spam scanner. Normally, such copies are deleted when they are no longer
24433 needed. If this control is set, the copies are not deleted. The control applies
24434 only to the current message, not to any subsequent ones that may be received in
24435 the same SMTP connection. It is provided for debugging purposes and is unlikely
24436 to be useful in production.
24438 .vitem &*control&~=&~no_multiline_response*&
24439 .cindex "multiline responses" "suppressing"
24440 This control is permitted for any ACL except the one for non-SMTP messages.
24441 It seems that there are broken clients in use that cannot handle multiline
24442 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
24444 If this control is set, multiline SMTP responses from ACL rejections are
24445 suppressed. One way of doing this would have been to put out these responses as
24446 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
24447 (&"use multiline responses for more"& it says &-- ha!), and some of the
24448 responses might get close to that. So this facility, which is after all only a
24449 sop to broken clients, is implemented by doing two very easy things:
24452 Extra information that is normally output as part of a rejection caused by
24453 sender verification failure is omitted. Only the final line (typically &"sender
24454 verification failed"&) is sent.
24456 If a &%message%& modifier supplies a multiline response, only the first
24460 The setting of the switch can, of course, be made conditional on the
24461 calling host. Its effect lasts until the end of the SMTP connection.
24463 .vitem &*control&~=&~queue_only*&
24464 .cindex "&%queue_only%&"
24465 .cindex "queueing incoming messages"
24466 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
24467 other words, only when a message is being received. If the message is accepted,
24468 it is placed on Exim's queue and left there for delivery by a subsequent queue
24469 runner. No immediate delivery process is started. In other words, it has the
24470 effect as the &%queue_only%& global option. However, the control applies only
24471 to the current message, not to any subsequent ones that may be received in the
24472 same SMTP connection.
24474 .vitem &*control&~=&~submission/*&<&'options'&>
24475 .cindex "message" "submission"
24476 .cindex "submission mode"
24477 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
24478 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
24479 the current message is a submission from a local MUA. In this case, Exim
24480 operates in &"submission mode"&, and applies certain fixups to the message if
24481 necessary. For example, it add a &'Date:'& header line if one is not present.
24482 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
24483 late (the message has already been created).
24485 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
24486 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
24487 submission mode; the available options for this control are described there.
24488 The control applies only to the current message, not to any subsequent ones
24489 that may be received in the same SMTP connection.
24491 .vitem &*control&~=&~suppress_local_fixups*&
24492 .cindex "submission fixups" "suppressing"
24493 This control applies to locally submitted (non TCP/IP) messages, and is the
24494 complement of &`control`& &`=`& &`submission`&. It disables the fixups that are
24495 normally applied to locally-submitted messages. Specifically:
24498 Any &'Sender:'& header line is left alone (in this respect, it is a
24499 dynamic version of &%local_sender_retain%&).
24501 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
24503 There is no check that &'From:'& corresponds to the actual sender.
24506 This feature may be useful when a remotely-originated message is accepted,
24507 passed to some scanning program, and then re-submitted for delivery.
24510 All four possibilities for message fixups can be specified:
24513 Locally submitted, fixups applied: the default.
24515 Locally submitted, no fixups applied: use &`control`& &`=`&
24516 &`suppress_local_fixups`&.
24518 Remotely submitted, no fixups applied: the default.
24520 Remotely submitted, fixups applied: use &`control`& &`=`& &`submission`&.
24526 .section "Adding header lines in ACLs" "SECTaddheadacl"
24527 .cindex "header lines" "adding in an ACL"
24528 .cindex "header lines" "position of added lines"
24529 .cindex "&%message%&" "ACL modifier"
24530 The &%add_header%& modifier can be used to add one or more extra header lines
24531 to an incoming message, as in this example:
24533 warn dnslists = sbl.spamhaus.org : \
24534 dialup.mail-abuse.org
24535 add_header = X-blacklisted-at: $dnslist_domain
24537 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
24538 MIME, and non-SMTP ACLs (in other words, those that are concerned with
24539 receiving a message). The message must ultimately be accepted for
24540 &%add_header%& to have any significant effect. You can use &%add_header%& with
24541 any ACL verb, including &%deny%& (though this is potentially useful only in a
24544 If the data for the &%add_header%& modifier contains one or more newlines that
24545 are not followed by a space or a tab, it is assumed to contain multiple header
24546 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
24547 front of any line that is not a valid header line.
24549 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
24550 They are added to the message before processing the DATA and MIME ACLs.
24551 However, if an identical header line is requested more than once, only one copy
24552 is actually added to the message. Further header lines may be accumulated
24553 during the DATA and MIME ACLs, after which they are added to the message, again
24554 with duplicates suppressed. Thus, it is possible to add two identical header
24555 lines to an SMTP message, but only if one is added before DATA and one after.
24556 In the case of non-SMTP messages, new headers are accumulated during the
24557 non-SMTP ACL, and added to the message at the end. If a message is rejected
24558 after DATA or by the non-SMTP ACL, all added header lines are included in the
24559 entry that is written to the reject log.
24561 .cindex "header lines" "added; visibility of"
24562 Header lines are not visible in string expansions until they are added to the
24563 message. It follows that header lines defined in the MAIL, RCPT, and predata
24564 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
24565 header lines that are added by the DATA or MIME ACLs are not visible in those
24566 ACLs. Because of this restriction, you cannot use header lines as a way of
24567 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
24568 this, you can use ACL variables, as described in section
24569 &<<SECTaclvariables>>&.
24571 The &%add_header%& modifier acts immediately it is encountered during the
24572 processing of an ACL. Notice the difference between these two cases:
24574 &`accept add_header = ADDED: some text`&
24575 &` `&<&'some condition'&>
24577 &`accept `&<&'some condition'&>
24578 &` add_header = ADDED: some text`&
24580 In the first case, the header line is always added, whether or not the
24581 condition is true. In the second case, the header line is added only if the
24582 condition is true. Multiple occurrences of &%add_header%& may occur in the same
24583 ACL statement. All those that are encountered before a condition fails are
24586 .cindex "&%warn%&" "ACL verb"
24587 For compatibility with previous versions of Exim, a &%message%& modifier for a
24588 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
24589 effect only if all the conditions are true, even if it appears before some of
24590 them. Furthermore, only the last occurrence of &%message%& is honoured. This
24591 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
24592 are present on a &%warn%& verb, both are processed according to their
24595 By default, new header lines are added to a message at the end of the existing
24596 header lines. However, you can specify that any particular header line should
24597 be added right at the start (before all the &'Received:'& lines), immediately
24598 after the first block of &'Received:'& lines, or immediately before any line
24599 that is not a &'Received:'& or &'Resent-something:'& header.
24601 This is done by specifying &":at_start:"&, &":after_received:"&, or
24602 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
24603 header line, respectively. (Header text cannot start with a colon, as there has
24604 to be a header name first.) For example:
24606 warn add_header = \
24607 :after_received:X-My-Header: something or other...
24609 If more than one header line is supplied in a single &%add_header%& modifier,
24610 each one is treated independently and can therefore be placed differently. If
24611 you add more than one line at the start, or after the Received: block, they end
24612 up in reverse order.
24614 &*Warning*&: This facility currently applies only to header lines that are
24615 added in an ACL. It does NOT work for header lines that are added in a
24616 system filter or in a router or transport.
24622 .section "ACL conditions" "SECTaclconditions"
24623 .cindex "&ACL;" "conditions; list of"
24624 Some of conditions listed in this section are available only when Exim is
24625 compiled with the content-scanning extension. They are included here briefly
24626 for completeness. More detailed descriptions can be found in the discussion on
24627 content scanning in chapter &<<CHAPexiscan>>&.
24629 Not all conditions are relevant in all circumstances. For example, testing
24630 senders and recipients does not make sense in an ACL that is being run as the
24631 result of the arrival of an ETRN command, and checks on message headers can be
24632 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
24633 can use the same condition (with different parameters) more than once in the
24634 same ACL statement. This provides a way of specifying an &"and"& conjunction.
24635 The conditions are as follows:
24639 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
24640 .cindex "&ACL;" "nested"
24641 .cindex "&ACL;" "indirect"
24642 .cindex "&%acl%&" "ACL condition"
24643 The possible values of the argument are the same as for the
24644 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
24645 &"accept"& the condition is true; if it returns &"deny"& the condition is
24646 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
24647 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
24648 condition false. This means that further processing of the &%warn%& verb
24649 ceases, but processing of the ACL continues.
24651 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
24652 the connection is dropped. If it returns &"discard"&, the verb must be
24653 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
24654 conditions are tested.
24656 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
24657 loops. This condition allows you to use different ACLs in different
24658 circumstances. For example, different ACLs can be used to handle RCPT commands
24659 for different local users or different local domains.
24661 .vitem &*authenticated&~=&~*&<&'string&~list'&>
24662 .cindex "&%authenticated%&" "ACL condition"
24663 .cindex "authentication" "ACL checking"
24664 .cindex "&ACL;" "testing for authentication"
24665 If the SMTP connection is not authenticated, the condition is false. Otherwise,
24666 the name of the authenticator is tested against the list. To test for
24667 authentication by any authenticator, you can set
24672 .vitem &*condition&~=&~*&<&'string'&>
24673 .cindex "&%condition%&" "ACL condition"
24674 .cindex "customizing" "ACL condition"
24675 .cindex "&ACL;" "customized test"
24676 .cindex "&ACL;" "testing; customized"
24677 This feature allows you to make up custom conditions. If the result of
24678 expanding the string is an empty string, the number zero, or one of the strings
24679 &"no"& or &"false"&, the condition is false. If the result is any non-zero
24680 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
24681 any other values, some error is assumed to have occurred, and the ACL returns
24684 .vitem &*decode&~=&~*&<&'location'&>
24685 .cindex "&%decode%&" "ACL condition"
24686 This condition is available only when Exim is compiled with the
24687 content-scanning extension, and it is allowed only the the ACL defined by
24688 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
24689 For details, see chapter &<<CHAPexiscan>>&.
24691 .vitem &*demime&~=&~*&<&'extension&~list'&>
24692 .cindex "&%demime%&" "ACL condition"
24693 This condition is available only when Exim is compiled with the
24694 content-scanning extension. Its use is described in section
24695 &<<SECTdemimecond>>&.
24697 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
24698 .cindex "&%dnslists%&" "ACL condition"
24699 .cindex "DNS list" "in ACL"
24700 .cindex "black list (DNS)"
24701 .cindex "&ACL;" "testing a DNS list"
24702 This condition checks for entries in DNS black lists. These are also known as
24703 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
24704 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
24705 different variants of this condition to describe briefly here. See sections
24706 &<<SECTmorednslists>>&--&<<SECTmorednslistslast>>& for details.
24708 .vitem &*domains&~=&~*&<&'domain&~list'&>
24709 .cindex "&%domains%&" "ACL condition"
24710 .cindex "domain" "ACL checking"
24711 .cindex "&ACL;" "testing a recipient domain"
24712 .cindex "&$domain_data$&"
24713 This condition is relevant only after a RCPT command. It checks that the domain
24714 of the recipient address is in the domain list. If percent-hack processing is
24715 enabled, it is done before this test is done. If the check succeeds with a
24716 lookup, the result of the lookup is placed in &$domain_data$& until the next
24719 .vitem &*encrypted&~=&~*&<&'string&~list'&>
24720 .cindex "&%encrypted%&" "ACL condition"
24721 .cindex "encryption" "checking in an ACL"
24722 .cindex "&ACL;" "testing for encryption"
24723 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
24724 name of the cipher suite in use is tested against the list. To test for
24725 encryption without testing for any specific cipher suite(s), set
24730 .vitem &*hosts&~=&~*&<&'&~host&~list'&>
24731 .cindex "&%hosts%&" "ACL condition"
24732 .cindex "host" "ACL checking"
24733 .cindex "&ACL;" "testing the client host"
24734 This condition tests that the calling host matches the host list. If you have
24735 name lookups or wildcarded host names and IP addresses in the same host list,
24736 you should normally put the IP addresses first. For example, you could have:
24738 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
24740 The reason for this lies in the left-to-right way that Exim processes lists.
24741 It can test IP addresses without doing any DNS lookups, but when it reaches an
24742 item that requires a host name, it fails if it cannot find a host name to
24743 compare with the pattern. If the above list is given in the opposite order, the
24744 &%accept%& statement fails for a host whose name cannot be found, even if its
24745 IP address is 10.9.8.7.
24747 If you really do want to do the name check first, and still recognize the IP
24748 address even if the name lookup fails, you can rewrite the ACL like this:
24750 accept hosts = dbm;/etc/friendly/hosts
24751 accept hosts = 10.9.8.7
24753 The default action on failing to find the host name is to assume that the host
24754 is not in the list, so the first &%accept%& statement fails. The second
24755 statement can then check the IP address.
24757 .cindex "&$host_data$&"
24758 If a &%hosts%& condition is satisfied by means of a lookup, the result
24759 of the lookup is made available in the &$host_data$& variable. This
24760 allows you, for example, to set up a statement like this:
24762 deny hosts = net-lsearch;/some/file
24763 message = $host_data
24765 which gives a custom error message for each denied host.
24767 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
24768 .cindex "&%local_parts%&" "ACL condition"
24769 .cindex "local part" "ACL checking"
24770 .cindex "&ACL;" "testing a local part"
24771 .cindex "&$local_part_data$&"
24772 This condition is relevant only after a RCPT command. It checks that the local
24773 part of the recipient address is in the list. If percent-hack processing is
24774 enabled, it is done before this test. If the check succeeds with a lookup, the
24775 result of the lookup is placed in &$local_part_data$&, which remains set until
24776 the next &%local_parts%& test.
24778 .vitem &*malware&~=&~*&<&'option'&>
24779 .cindex "&%malware%&" "ACL condition"
24780 .cindex "&ACL;" "virus scanning"
24781 .cindex "&ACL;" "scanning for viruses"
24782 This condition is available only when Exim is compiled with the
24783 content-scanning extension. It causes the incoming message to be scanned for
24784 viruses. For details, see chapter &<<CHAPexiscan>>&.
24786 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
24787 .cindex "&%mime_regex%&" "ACL condition"
24788 .cindex "&ACL;" "testing by regex matching"
24789 This condition is available only when Exim is compiled with the
24790 content-scanning extension, and it is allowed only the the ACL defined by
24791 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
24792 with any of the regular expressions. For details, see chapter
24795 .vitem &*ratelimit&~=&~*&<&'parameters'&>
24796 .cindex "rate limiting"
24797 This condition can be used to limit the rate at which a user or host submits
24798 messages. Details are given in section &<<SECTratelimiting>>&.
24800 .vitem &*recipients&~=&~*&<&'address&~list'&>
24801 .cindex "&%recipients%&" "ACL condition"
24802 .cindex "recipient" "ACL checking"
24803 .cindex "&ACL;" "testing a recipient"
24804 This condition is relevant only after a RCPT command. It checks the entire
24805 recipient address against a list of recipients.
24807 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
24808 .cindex "&%regex%&" "ACL condition"
24809 .cindex "&ACL;" "testing by regex matching"
24810 This condition is available only when Exim is compiled with the
24811 content-scanning extension, and is available only in the DATA, MIME, and
24812 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
24813 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
24815 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
24816 .cindex "&%sender_domains%&" "ACL condition"
24817 .cindex "sender" "ACL checking"
24818 .cindex "&ACL;" "testing a sender domain"
24819 .cindex "&$domain$&"
24820 .cindex "&$sender_address_domain$&"
24821 This condition tests the domain of the sender of the message against the given
24822 domain list. &*Note*&: The domain of the sender address is in
24823 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
24824 of this condition. This is an exception to the general rule for testing domain
24825 lists. It is done this way so that, if this condition is used in an ACL for a
24826 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
24827 influence the sender checking.
24829 &*Warning*&: It is a bad idea to use this condition on its own as a control on
24830 relaying, because sender addresses are easily, and commonly, forged.
24832 .vitem &*senders&~=&~*&<&'address&~list'&>
24833 .cindex "&%senders%&" "ACL condition"
24834 .cindex "sender" "ACL checking"
24835 .cindex "&ACL;" "testing a sender"
24836 This condition tests the sender of the message against the given list. To test
24837 for a bounce message, which has an empty sender, set
24841 &*Warning*&: It is a bad idea to use this condition on its own as a control on
24842 relaying, because sender addresses are easily, and commonly, forged.
24844 .vitem &*spam&~=&~*&<&'username'&>
24845 .cindex "&%spam%&" "ACL condition"
24846 .cindex "&ACL;" "scanning for spam"
24847 This condition is available only when Exim is compiled with the
24848 content-scanning extension. It causes the incoming message to be scanned by
24849 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
24851 .vitem &*verify&~=&~certificate*&
24852 .cindex "&%verify%&" "ACL condition"
24853 .cindex "TLS" "client certificate verification"
24854 .cindex "certificate" "verification of client"
24855 .cindex "&ACL;" "certificate verification"
24856 .cindex "&ACL;" "testing a TLS certificate"
24857 This condition is true in an SMTP session if the session is encrypted, and a
24858 certificate was received from the client, and the certificate was verified. The
24859 server requests a certificate only if the client matches &%tls_verify_hosts%&
24860 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
24862 .vitem &*verify&~=&~csa*&
24863 .cindex "CSA verification"
24864 This condition checks whether the sending host (the client) is authorized to
24865 send email. Details of how this works are given in section
24866 &<<SECTverifyCSA>>&.
24868 .vitem &*verify&~=&~header_sender/*&<&'options'&>
24869 .cindex "&%verify%&" "ACL condition"
24870 .cindex "&ACL;" "verifying sender in the header"
24871 .cindex "header lines" "verifying the sender in"
24872 .cindex "sender" "verifying in header"
24873 .cindex "verifying" "sender in header"
24874 This condition is relevant only in an ACL that is run after a message has been
24875 received, that is, in an ACL specified by &%acl_smtp_data%& or
24876 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
24877 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
24878 is loosely thought of as a &"sender"& address (hence the name of the test).
24879 However, an address that appears in one of these headers need not be an address
24880 that accepts bounce messages; only sender addresses in envelopes are required
24881 to accept bounces. Therefore, if you use the callout option on this check, you
24882 might want to arrange for a non-empty address in the MAIL command.
24884 Details of address verification and the options are given later, starting at
24885 section &<<SECTaddressverification>>& (callouts are described in section
24886 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
24887 condition to restrict it to bounce messages only:
24890 message = A valid sender header is required for bounces
24891 !verify = header_sender
24894 .vitem &*verify&~=&~header_syntax*&
24895 .cindex "&%verify%&" "ACL condition"
24896 .cindex "&ACL;" "verifying header syntax"
24897 .cindex "header lines" "verifying syntax"
24898 .cindex "verifying" "header syntax"
24899 This condition is relevant only in an ACL that is run after a message has been
24900 received, that is, in an ACL specified by &%acl_smtp_data%& or
24901 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
24902 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
24903 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
24904 permitted only in locally generated messages and from hosts that match
24905 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24908 Note that this condition is a syntax check only. However, a common spamming
24909 ploy used to be to send syntactically invalid headers such as
24913 and this condition can be used to reject such messages, though they are not as
24914 common as they used to be.
24916 .vitem &*verify&~=&~helo*&
24917 .cindex "&%verify%&" "ACL condition"
24918 .cindex "&ACL;" "verifying HELO/EHLO"
24919 .cindex "HELO" "verifying"
24920 .cindex "EHLO" "verifying"
24921 .cindex "verifying" "EHLO"
24922 .cindex "verifying" "HELO"
24923 This condition is true if a HELO or EHLO command has been received from the
24924 client host, and its contents have been verified. It there has been no previous
24925 attempt to verify the the HELO/EHLO contents, it is carried out when this
24926 condition is encountered. See the description of the &%helo_verify_hosts%& and
24927 &%helo_try_verify_hosts%& options for details of how to request verification
24928 independently of this condition.
24930 .vitem &*verify&~=&~not_blind*&
24931 .cindex "verifying" "not blind"
24932 .cindex "bcc recipients" "verifying none"
24933 This condition checks that there are no blind (bcc) recipients in the message.
24934 Every envelope recipient must appear either in a &'To:'& header line or in a
24935 &'Cc:'& header line for this condition to be true. Local parts are checked
24936 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
24937 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
24938 used only in a DATA or non-SMTP ACL.
24940 There are, of course, many legitimate messages that make use of blind (bcc)
24941 recipients. This check should not be used on its own for blocking messages.
24944 .vitem &*verify&~=&~recipient/*&<&'options'&>
24945 .cindex "&%verify%&" "ACL condition"
24946 .cindex "&ACL;" "verifying recipient"
24947 .cindex "recipient" "verifying"
24948 .cindex "verifying" "recipient"
24949 .cindex "&$address_data$&"
24950 This condition is relevant only after a RCPT command. It verifies the current
24951 recipient. Details of address verification are given later, starting at section
24952 &<<SECTaddressverification>>&. After a recipient has been verified, the value
24953 of &$address_data$& is the last value that was set while routing the address.
24954 This applies even if the verification fails. When an address that is being
24955 verified is redirected to a single address, verification continues with the new
24956 address, and in that case, the subsequent value of &$address_data$& is the
24957 value for the child address.
24959 .vitem &*verify&~=&~reverse_host_lookup*&
24960 .cindex "&%verify%&" "ACL condition"
24961 .cindex "&ACL;" "verifying host reverse lookup"
24962 .cindex "host" "verifying reverse lookup"
24963 This condition ensures that a verified host name has been looked up from the IP
24964 address of the client host. (This may have happened already if the host name
24965 was needed for checking a host list, or if the host matched &%host_lookup%&.)
24966 Verification ensures that the host name obtained from a reverse DNS lookup, or
24967 one of its aliases, does, when it is itself looked up in the DNS, yield the
24968 original IP address.
24970 If this condition is used for a locally generated message (that is, when there
24971 is no client host involved), it always succeeds.
24973 .vitem &*verify&~=&~sender/*&<&'options'&>
24974 .cindex "&%verify%&" "ACL condition"
24975 .cindex "&ACL;" "verifying sender"
24976 .cindex "sender" "verifying"
24977 .cindex "verifying" "sender"
24978 This condition is relevant only after a MAIL or RCPT command, or after a
24979 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
24980 the message's sender is empty (that is, this is a bounce message), the
24981 condition is true. Otherwise, the sender address is verified.
24983 .cindex "&$address_data$&"
24984 .cindex "&$sender_address_data$&"
24985 If there is data in the &$address_data$& variable at the end of routing, its
24986 value is placed in &$sender_address_data$& at the end of verification. This
24987 value can be used in subsequent conditions and modifiers in the same ACL
24988 statement. It does not persist after the end of the current statement. If you
24989 want to preserve the value for longer, you can save it in an ACL variable.
24991 Details of verification are given later, starting at section
24992 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
24993 to avoid doing it more than once per message.
24995 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
24996 .cindex "&%verify%&" "ACL condition"
24997 This is a variation of the previous option, in which a modified address is
24998 verified as a sender.
25003 .section "Using DNS lists" "SECTmorednslists"
25004 .cindex "DNS list" "in ACL"
25005 .cindex "black list (DNS)"
25006 .cindex "&ACL;" "testing a DNS list"
25007 In its simplest form, the &%dnslists%& condition tests whether the calling host
25008 is on at least one of a number of DNS lists by looking up the inverted IP
25009 address in one or more DNS domains. For example, if the calling host's IP
25010 address is 192.168.62.43, and the ACL statement is
25012 deny dnslists = blackholes.mail-abuse.org : \
25013 dialups.mail-abuse.org
25015 the following records are looked up:
25017 43.62.168.192.blackholes.mail-abuse.org
25018 43.62.168.192.dialups.mail-abuse.org
25020 As soon as Exim finds an existing DNS record, processing of the list stops.
25021 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
25022 to test that a host is on more than one list (an &"and"& conjunction), you can
25023 use two separate conditions:
25025 deny dnslists = blackholes.mail-abuse.org
25026 dnslists = dialups.mail-abuse.org
25028 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
25029 behaves as if the host does not match the list item, that is, as if the DNS
25030 record does not exist. If there are further items in the DNS list, they are
25033 This is usually the required action when &%dnslists%& is used with &%deny%&
25034 (which is the most common usage), because it prevents a DNS failure from
25035 blocking mail. However, you can change this behaviour by putting one of the
25036 following special items in the list:
25038 &`+include_unknown `& behave as if the item is on the list
25039 &`+exclude_unknown `& behave as if the item is not on the list (default)
25040 &`+defer_unknown `& give a temporary error
25042 .cindex "&`+include_unknown`&"
25043 .cindex "&`+exclude_unknown`&"
25044 .cindex "&`+defer_unknown`&"
25045 Each of these applies to any subsequent items on the list. For example:
25047 deny dnslists = +defer_unknown : foo.bar.example
25049 Testing the list of domains stops as soon as a match is found. If you want to
25050 warn for one list and block for another, you can use two different statements:
25052 deny dnslists = blackholes.mail-abuse.org
25053 warn message = X-Warn: sending host is on dialups list
25054 dnslists = dialups.mail-abuse.org
25056 DNS list lookups are cached by Exim for the duration of the SMTP session,
25057 so a lookup based on the IP address is done at most once for any incoming
25058 connection. Exim does not share information between multiple incoming
25059 connections (but your local name server cache should be active).
25063 .section "Specifying the IP address for a DNS list lookup"
25064 .cindex "DNS list" "keyed by explicit IP address"
25065 By default, the IP address that is used in a DNS list lookup is the IP address
25066 of the calling host. However, you can specify another IP address by listing it
25067 after the domain name, introduced by a slash. For example:
25069 deny dnslists = black.list.tld/192.168.1.2
25071 This feature is not very helpful with explicit IP addresses; it is intended for
25072 use with IP addresses that are looked up, for example, the IP addresses of the
25073 MX hosts or nameservers of an email sender address. For an example, see section
25074 &<<SECTmulkeyfor>>& below.
25079 .section "DNS lists keyed on domain names"
25080 .cindex "DNS list" "keyed by domain name"
25081 There are some lists that are keyed on domain names rather than inverted IP
25082 addresses (see for example the &'domain based zones'& link at
25083 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
25084 with these lists. You can change the name that is looked up in a DNS list by
25085 listing it after the domain name, introduced by a slash. For example,
25087 deny message = Sender's domain is listed at $dnslist_domain
25088 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
25090 This particular example is useful only in ACLs that are obeyed after the
25091 RCPT or DATA commands, when a sender address is available. If (for
25092 example) the message's sender is &'user@tld.example'& the name that is looked
25093 up by this example is
25095 tld.example.dsn.rfc-ignorant.org
25097 A single &%dnslists%& condition can contain entries for both names and IP
25098 addresses. For example:
25100 deny dnslists = sbl.spamhaus.org : \
25101 dsn.rfc-ignorant.org/$sender_address_domain
25103 The first item checks the sending host's IP address; the second checks a domain
25104 name. The whole condition is true if either of the DNS lookups succeeds.
25109 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
25110 .cindex "DNS list" "multiple keys for"
25111 The syntax described above for looking up explicitly-defined values (either
25112 names or IP addresses) in a DNS blacklist is a simplification. After the domain
25113 name for the DNS list, what follows the slash can in fact be a list of items.
25114 As with all lists in Exim, the default separator is a colon. However, because
25115 this is a sublist within the list of DNS blacklist domains, it is necessary
25116 either to double the separators like this:
25118 dnslists = black.list.tld/name.1::name.2
25120 or to change the separator character, like this:
25122 dnslists = black.list.tld/<;name.1;name.2
25124 If an item in the list is an IP address, it is inverted before the DNS
25125 blacklist domain is appended. If it is not an IP address, no inversion
25126 occurs. Consider this condition:
25128 dnslists = black.list.tld/<;192.168.1.2;a.domain
25130 The DNS lookups that occur are:
25132 2.1.168.192.black.list.tld
25133 a.domain.black.list.tld
25135 Once a DNS record has been found (that matches a specific IP return
25136 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
25137 are done. If there is a temporary DNS error, the rest of the sublist of domains
25138 or IP addresses is tried. A temporary error for the whole dnslists item occurs
25139 only if no other DNS lookup in this sublist succeeds. In other words, a
25140 successful lookup for any of the items in the sublist overrides a temporary
25141 error for a previous item.
25143 The ability to supply a list of items after the slash is in some sense just a
25144 syntactic convenience. These two examples have the same effect:
25146 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
25147 dnslists = black.list.tld/a.domain::b.domain
25149 However, when the data for the list is obtained from a lookup, the second form
25150 is usually much more convenient. Consider this example:
25152 deny message = The mail servers for the domain \
25153 $sender_address_domain \
25154 are listed at $dnslist_domain ($dnslist_value); \
25156 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
25157 ${lookup dnsdb {>|mxh=\
25158 $sender_address_domain} }} }
25160 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
25161 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
25162 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
25163 of expanding the condition might be something like this:
25165 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
25167 Thus, this example checks whether or not the IP addresses of the sender
25168 domain's mail servers are on the Spamhaus black list.
25174 .section "Data returned by DNS lists"
25175 .cindex "DNS list" "data returned from"
25176 DNS lists are constructed using address records in the DNS. The original RBL
25177 just used the address 127.0.0.1 on the right hand side of each record, but the
25178 RBL+ list and some other lists use a number of values with different meanings.
25179 The values used on the RBL+ list are:
25183 127.1.0.3 DUL and RBL
25185 127.1.0.5 RSS and RBL
25186 127.1.0.6 RSS and DUL
25187 127.1.0.7 RSS and DUL and RBL
25189 Some DNS lists may return more than one address record.
25192 .section "Variables set from DNS lists"
25193 .cindex "DNS list" "variables set from"
25194 .cindex "&$dnslist_domain$&"
25195 .cindex "&$dnslist_text$&"
25196 .cindex "&$dnslist_value$&"
25197 When an entry is found in a DNS list, the variable &$dnslist_domain$&
25198 contains the name of the domain that matched, &$dnslist_value$& contains the
25199 data from the entry, and &$dnslist_text$& contains the contents of any
25200 associated TXT record. If more than one address record is returned by the DNS
25201 lookup, all the IP addresses are included in &$dnslist_value$&, separated by
25204 You can use these variables in &%message%& or &%log_message%& modifiers &--
25205 although these appear before the condition in the ACL, they are not expanded
25206 until after it has failed. For example:
25208 deny hosts = !+local_networks
25209 message = $sender_host_address is listed \
25211 dnslists = rbl-plus.mail-abuse.example
25216 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
25217 .cindex "DNS list" "matching specific returned data"
25218 You can add an equals sign and an IP address after a &%dnslists%& domain name
25219 in order to restrict its action to DNS records with a matching right hand side.
25222 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
25224 rejects only those hosts that yield 127.0.0.2. Without this additional data,
25225 any address record is considered to be a match. If more than one address record
25226 is found on the list, they are all checked for a matching right-hand side.
25228 More than one IP address may be given for checking, using a comma as a
25229 separator. These are alternatives &-- if any one of them matches, the
25230 &%dnslists%& condition is true. For example:
25232 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
25234 If you want to specify a constraining address list and also specify names or IP
25235 addresses to be looked up, the constraining address list must be specified
25236 first. For example:
25238 deny dnslists = dsn.rfc-ignorant.org\
25239 =127.0.0.2/$sender_address_domain
25242 If the character &`&&`& is used instead of &`=`&, the comparison for each
25243 listed IP address is done by a bitwise &"and"& instead of by an equality test.
25244 In other words, the listed addresses are used as bit masks. The comparison is
25245 true if all the bits in the mask are present in the address that is being
25246 tested. For example:
25248 dnslists = a.b.c&0.0.0.3
25250 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
25251 want to test whether one bit or another bit is present (as opposed to both
25252 being present), you must use multiple values. For example:
25254 dnslists = a.b.c&0.0.0.1,0.0.0.2
25256 matches if the final component of the address is an odd number or two times
25261 .section "Negated DNS matching conditions"
25262 You can supply a negative list of IP addresses as part of a &%dnslists%&
25265 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
25267 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
25268 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
25270 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
25272 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
25273 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
25274 words, the result of the test is inverted if an exclamation mark appears before
25275 the &`=`& (or the &`&&`&) sign.
25277 &*Note*&: This kind of negation is not the same as negation in a domain,
25278 host, or address list (which is why the syntax is different).
25280 If you are using just one list, the negation syntax does not gain you much. The
25281 previous example is precisely equivalent to
25283 deny dnslists = a.b.c
25284 !dnslists = a.b.c=127.0.0.2,127.0.0.3
25286 However, if you are using multiple lists, the negation syntax is clearer.
25287 Consider this example:
25289 deny dnslists = sbl.spamhaus.org : \
25291 dnsbl.njabl.org!=127.0.0.3 : \
25294 Using only positive lists, this would have to be:
25296 deny dnslists = sbl.spamhaus.org : \
25298 deny dnslists = dnsbl.njabl.org
25299 !dnslists = dnsbl.njabl.org=127.0.0.3
25300 deny dnslists = relays.ordb.org
25302 which is less clear, and harder to maintain.
25307 .section "DNS lists and IPv6" "SECTmorednslistslast"
25308 .cindex "IPv6" "DNS black lists"
25309 .cindex "DNS list" "IPv6 usage"
25310 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
25311 nibble by nibble. For example, if the calling host's IP address is
25312 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
25314 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
25315 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
25317 (split over two lines here to fit on the page). Unfortunately, some of the DNS
25318 lists contain wildcard records, intended for IPv4, that interact badly with
25319 IPv6. For example, the DNS entry
25321 *.3.some.list.example. A 127.0.0.1
25323 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
25324 Unfortunately, it also matches the entire 3::/4 IPv6 network.
25326 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
25327 &%condition%& condition, as in this example:
25329 deny condition = ${if isip4{$sender_host_address}}
25330 dnslists = some.list.example
25333 .section "Rate limiting senders" "SECTratelimiting"
25334 .cindex "rate limiting" "client sending"
25335 .cindex "limiting client sending rates"
25336 .oindex "&%smpt_ratelimit_*%&"
25337 The &%ratelimit%& ACL condition can be used to measure and control the rate at
25338 which clients can send email. This is more powerful than the
25339 &%smtp_ratelimit_*%& options, because those options control the rate of
25340 commands in a single SMTP session only, whereas the &%ratelimit%& condition
25341 works across all connections (concurrent and sequential) from the same client
25342 host. The syntax of the &%ratelimit%& condition is:
25344 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
25346 If the average client sending rate is less than &'m'& messages per time
25347 period &'p'& then the condition is false; otherwise it is true.
25349 As a side-effect, the &%ratelimit%& condition sets the expansion variable
25350 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
25351 configured value of &'m'&, and &$sender_rate_period$& to the configured value
25354 The parameter &'p'& is the smoothing time constant, in the form of an Exim
25355 time interval, for example, &`8h`& for eight hours. A larger time constant
25356 means that it takes Exim longer to forget a client's past behaviour. The
25357 parameter &'m'& is the maximum number of messages that a client is permitted to
25358 send in each time interval. It also specifies the number of messages permitted
25359 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
25360 constant, you can allow a client to send more messages in a burst without
25361 changing its overall sending rate limit. Conversely, if &'m'& and &'p'& are
25362 both small, messages must be sent at an even rate.
25364 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
25365 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
25366 when deploying the &%ratelimit%& ACL condition. The script prints usage
25367 instructions when it is run with no arguments.
25369 The key is used to look up the data for calculating the client's average
25370 sending rate. This data is stored in a database maintained by Exim in its spool
25371 directory, alongside the retry and other hints databases. The default key is
25372 &$sender_host_address$&, which applies the limit to each client host IP address.
25373 By changing the key you can change how Exim identifies clients for the purpose
25374 of ratelimiting. For example, to limit the sending rate of each authenticated
25375 user, independent of the computer they are sending from, set the key to
25376 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
25377 example, &$authenticated_id$& is only meaningful if the client has
25378 authenticated, and you can check with with the &%authenticated%& ACL condition.
25380 Internally, Exim includes the smoothing constant &'p'& and the options in the
25381 lookup key because they alter the meaning of the stored data. This is not true
25382 for the limit &'m'&, so you can alter the configured maximum rate and Exim will
25383 still remember clients' past behaviour, but if you alter the other ratelimit
25384 parameters Exim forgets past behaviour.
25386 Each &%ratelimit%& condition can have up to two options. The first option
25387 specifies what Exim measures the rate of, and the second specifies how Exim
25388 handles excessively fast clients. The options are separated by a slash, like
25389 the other parameters.
25391 The &%per_conn%& option limits the client's connection rate.
25393 The &%per_mail%& option limits the client's rate of sending messages. This is
25394 the default if none of the &%per_*%& options is specified.
25396 The &%per_byte%& option limits the sender's email bandwidth. Note that it is
25397 best to use this option in the DATA ACL; if it is used in an earlier ACL it
25398 relies on the SIZE parameter on the MAIL command, which may be inaccurate or
25399 completely missing. You can follow the limit &'m'& in the configuration with K,
25400 M, or G to specify limits in kilobytes, megabytes, or gigabytes, respectively.
25402 The &%per_cmd%& option causes Exim to recompute the rate every time the
25403 condition is processed. This can be used to limit the SMTP command rate. The
25404 alias &%per_rcpt%& is provided for use in the RCPT ACL instead of &%per_cmd%&
25405 to make it clear that the effect is to limit the rate at which recipients are
25406 accepted. Note that in this case the rate limiting engine will see a message
25407 with many recipients as a large high-speed burst.
25409 If a client's average rate is greater than the maximum, the rate limiting
25410 engine can react in two possible ways, depending on the presence of the
25411 &%strict%& or &%leaky%& options. This is independent of the other
25412 counter-measures (such as rejecting the message) that may be specified by the
25413 rest of the ACL. The default mode is leaky, which avoids a sender's
25414 over-aggressive retry rate preventing it from getting any email through.
25416 The &%strict%& option means that the client's recorded rate is always updated.
25417 The effect of this is that Exim measures the client's average rate of attempts
25418 to send email, which can be much higher than the maximum. If the client is over
25419 the limit it will be subjected to counter-measures until it slows down below
25420 the maximum rate. The smoothing period determines the time it takes for a high
25421 sending rate to decay exponentially to 37% of its peak value, which means that
25422 you can work out the time (the number of smoothing periods) that a client is
25423 subjected to counter-measures after an over-limit burst with this formula:
25425 ln(peakrate/maxrate)
25427 The &%leaky%& option means that the client's recorded rate is not updated if it
25428 is above the limit. The effect of this is that Exim measures the client's
25429 average rate of successfully sent email, which cannot be greater than the
25430 maximum. If the client is over the limit it will suffer some counter-measures,
25431 but it will still be able to send email at the configured maximum rate,
25432 whatever the rate of its attempts. This is generally the better choice if you
25433 have clients that retry automatically.
25435 Exim's other ACL facilities are used to define what counter-measures are taken
25436 when the rate limit is exceeded. This might be anything from logging a warning
25437 (for example, while measuring existing sending rates in order to define
25438 policy), through time delays to slow down fast senders, up to rejecting the
25439 message. For example:
25441 # Log all senders' rates
25443 ratelimit = 0 / 1h / strict
25444 log_message = Sender rate $sender_rate / $sender_rate_period
25446 # Slow down fast senders; note the need to truncate $sender_rate
25447 # at the decimal point.
25449 ratelimit = 100 / 1h / per_rcpt / strict
25450 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
25451 $sender_rate_limit }s
25453 # Keep authenticated users under control
25456 ratelimit = 100 / 1d / strict / $authenticated_id
25458 # System-wide rate limit
25460 message = Sorry, too busy. Try again later.
25461 ratelimit = 10 / 1s / $primary_hostname
25463 # Restrict incoming rate from each host, with a default
25464 # set using a macro and special cases looked up in a table.
25466 message = Sender rate exceeds $sender_rate_limit \
25467 messages per $sender_rate_period
25468 ratelimit = ${lookup {$sender_host_address} \
25469 cdb {DB/ratelimits.cdb} \
25470 {$value} {RATELIMIT} }
25472 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
25473 especially with the &%per_rcpt%& option, you may suffer from a performance
25474 bottleneck caused by locking on the ratelimit hints database. Apart from
25475 making your ACLs less complicated, you can reduce the problem by using a
25476 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
25477 this means that Exim will lose its hints data after a reboot (including retry
25478 hints, the callout cache, and ratelimit data).
25481 .section "Address verification" "SECTaddressverification"
25482 .cindex "verifying address" "options for"
25483 .cindex "policy control" "address verification"
25484 Several of the &%verify%& conditions described in section
25485 &<<SECTaclconditions>>& cause addresses to be verified. These conditions can be
25486 followed by options that modify the verification process. The options are
25487 separated from the keyword and from each other by slashes, and some of them
25488 contain parameters. For example:
25490 verify = sender/callout
25491 verify = recipient/defer_ok/callout=10s,defer_ok
25493 The first stage of address verification, which always happens, is to run the
25494 address through the routers, in &"verify mode"&. Routers can detect the
25495 difference between verification and routing for delivery, and their actions can
25496 be varied by a number of generic options such as &%verify%& and &%verify_only%&
25497 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
25498 The available options are as follows:
25501 If the &%callout%& option is specified, successful routing to one or more
25502 remote hosts is followed by a &"callout"& to those hosts as an additional
25503 check. Callouts and their sub-options are discussed in the next section.
25505 If there is a defer error while doing verification routing, the ACL
25506 normally returns &"defer"&. However, if you include &%defer_ok%& in the
25507 options, the condition is forced to be true instead. Note that this is a main
25508 verification option as well as a suboption for callouts.
25510 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
25511 discusses the reporting of sender address verification failures.
25513 The &%success_on_redirect%& option causes verification always to succeed
25514 immediately after a successful redirection. By default, if a redirection
25515 generates just one address, that address is also verified. See further
25516 discussion in section &<<SECTredirwhilveri>>&.
25519 .cindex "verifying address" "differentiating failures"
25520 .cindex "&$recipient_verify_failure$&"
25521 .cindex "&$sender_verify_failure$&"
25522 .cindex "&$acl_verify_message$&"
25523 After an address verification failure, &$acl_verify_message$& contains the
25524 error message that is associated with the failure. It can be preserved by
25527 warn !verify = sender
25528 set acl_m0 = $acl_verify_message
25530 If you are writing your own custom rejection message or log message when
25531 denying access, you can use this variable to include information about the
25532 verification failure.
25534 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
25535 appropriate) contains one of the following words:
25538 &%qualify%&: The address was unqualified (no domain), and the message
25539 was neither local nor came from an exempted host.
25541 &%route%&: Routing failed.
25543 &%mail%&: Routing succeeded, and a callout was attempted; rejection
25544 occurred at or before the MAIL command (that is, on initial
25545 connection, HELO, or MAIL).
25547 &%recipient%&: The RCPT command in a callout was rejected.
25549 &%postmaster%&: The postmaster check in a callout was rejected.
25552 The main use of these variables is expected to be to distinguish between
25553 rejections of MAIL and rejections of RCPT in callouts.
25558 .section "Callout verification" "SECTcallver"
25559 .cindex "verifying address" "by callout"
25560 .cindex "callout" "verification"
25561 .cindex "SMTP" "callout verification"
25562 For non-local addresses, routing verifies the domain, but is unable to do any
25563 checking of the local part. There are situations where some means of verifying
25564 the local part is desirable. One way this can be done is to make an SMTP
25565 &'callback'& to a delivery host for the sender address or a &'callforward'& to
25566 a subsequent host for a recipient address, to see if the host accepts the
25567 address. We use the term &'callout'& to cover both cases. Note that for a
25568 sender address, the callback is not to the client host that is trying to
25569 deliver the message, but to one of the hosts that accepts incoming mail for the
25572 Exim does not do callouts by default. If you want them to happen, you must
25573 request them by setting appropriate options on the &%verify%& condition, as
25574 described below. This facility should be used with care, because it can add a
25575 lot of resource usage to the cost of verifying an address. However, Exim does
25576 cache the results of callouts, which helps to reduce the cost. Details of
25577 caching are in section &<<SECTcallvercache>>&.
25579 Recipient callouts are usually used only between hosts that are controlled by
25580 the same administration. For example, a corporate gateway host could use
25581 callouts to check for valid recipients on an internal mailserver. A successful
25582 callout does not guarantee that a real delivery to the address would succeed;
25583 on the other hand, a failing callout does guarantee that a delivery would fail.
25585 If the &%callout%& option is present on a condition that verifies an address, a
25586 second stage of verification occurs if the address is successfully routed to
25587 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
25588 &(manualroute)& router, where the router specifies the hosts. However, if a
25589 router that does not set up hosts routes to an &(smtp)& transport with a
25590 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
25591 &%hosts_override%& set, its hosts are always used, whether or not the router
25592 supplies a host list.
25594 The port that is used is taken from the transport, if it is specified and is a
25595 remote transport. (For routers that do verification only, no transport need be
25596 specified.) Otherwise, the default SMTP port is used. If a remote transport
25597 specifies an outgoing interface, this is used; otherwise the interface is not
25600 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
25601 test whether a bounce message could be delivered to the sender address. The
25602 following SMTP commands are sent:
25604 &`HELO `&<&'smtp active host name'&>
25606 &`RCPT TO:`&<&'the address to be tested'&>
25609 LHLO is used instead of HELO if the transport's &%protocol%& option is
25612 A recipient callout check is similar. By default, it also uses an empty address
25613 for the sender. This default is chosen because most hosts do not make use of
25614 the sender address when verifying a recipient. Using the same address means
25615 that a single cache entry can be used for each recipient. Some sites, however,
25616 do make use of the sender address when verifying. These are catered for by the
25617 &%use_sender%& and &%use_postmaster%& options, described in the next section.
25619 If the response to the RCPT command is a 2&'xx'& code, the verification
25620 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
25621 Exim tries the next host, if any. If there is a problem with all the remote
25622 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
25623 &%callout%& option is given, in which case the condition is forced to succeed.
25629 .section "Additional parameters for callouts" "CALLaddparcall"
25630 .cindex "callout" "additional parameters for"
25631 The &%callout%& option can be followed by an equals sign and a number of
25632 optional parameters, separated by commas. For example:
25634 verify = recipient/callout=10s,defer_ok
25636 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
25637 separate verify options, is retained for backwards compatibility, but is now
25638 deprecated. The additional parameters for &%callout%& are as follows:
25642 .vitem <&'a&~time&~interval'&>
25643 .cindex "callout timeout" "specifying"
25644 This specifies the timeout that applies for the callout attempt to each host.
25647 verify = sender/callout=5s
25649 The default is 30 seconds. The timeout is used for each response from the
25650 remote host. It is also used for the intial connection, unless overridden by
25651 the &%connect%& parameter.
25654 .vitem &*connect&~=&~*&<&'time&~interval'&>
25655 .cindex "callout connection timeout" "specifying"
25656 This parameter makes it possible to set a different (usually smaller) timeout
25657 for making the SMTP connection. For example:
25659 verify = sender/callout=5s,connect=1s
25661 If not specified, this timeout defaults to the general timeout value.
25663 .vitem &*defer_ok*&
25664 .cindex "callout defer" "action on"
25665 When this parameter is present, failure to contact any host, or any other kind
25666 of temporary error, is treated as success by the ACL. However, the cache is not
25667 updated in this circumstance.
25669 .vitem &*fullpostmaster*&
25670 .cindex "callout" "full postmaster check"
25671 This operates like the &%postmaster%& option (see below), but if the check for
25672 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
25673 accordance with the specification in RFC 2821. The RFC states that the
25674 unqualified address &'postmaster'& should be accepted.
25677 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
25678 .cindex "callout" "sender when verifying header"
25679 When verifying addresses in header lines using the &%header_sender%&
25680 verification option, Exim behaves by default as if the addresses are envelope
25681 sender addresses from a message. Callout verification therefore tests to see
25682 whether a bounce message could be delivered, by using an empty address in the
25683 MAIL command. However, it is arguable that these addresses might never be used
25684 as envelope senders, and could therefore justifiably reject bounce messages
25685 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
25686 address to use in the MAIL command. For example:
25688 require verify = header_sender/callout=mailfrom=abcd@x.y.z
25690 This parameter is available only for the &%header_sender%& verification option.
25693 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
25694 .cindex "callout overall timeout" "specifying"
25695 This parameter sets an overall timeout for performing a callout verification.
25698 verify = sender/callout=5s,maxwait=30s
25700 This timeout defaults to four times the callout timeout for individual SMTP
25701 commands. The overall timeout applies when there is more than one host that can
25702 be tried. The timeout is checked before trying the next host. This prevents
25703 very long delays if there are a large number of hosts and all are timing out
25704 (for example, when network connections are timing out).
25707 .vitem &*no_cache*&
25708 .cindex "callout cache" "suppressing"
25709 .cindex "caching callout" "suppressing"
25710 When this parameter is given, the callout cache is neither read nor updated.
25712 .vitem &*postmaster*&
25713 .cindex "callout" "postmaster; checking"
25714 When this parameter is set, a sucessful callout check is followed by a similar
25715 check for the local part &'postmaster'& at the same domain. If this address is
25716 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
25717 the postmaster check is recorded in a cache record; if it is a failure, this is
25718 used to fail subsequent callouts for the domain without a connection being
25719 made, until the cache record expires.
25721 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
25722 The postmaster check uses an empty sender in the MAIL command by default.
25723 You can use this parameter to do a postmaster check using a different address.
25726 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
25728 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
25729 one overrides. The &%postmaster%& parameter is equivalent to this example:
25731 require verify = sender/callout=postmaster_mailfrom=
25733 &*Warning*&: The caching arrangements for postmaster checking do not take
25734 account of the sender address. It is assumed that either the empty address or
25735 a fixed non-empty address will be used. All that Exim remembers is that the
25736 postmaster check for the domain succeeded or failed.
25740 .cindex "callout" "&""random""& check"
25741 When this parameter is set, before doing the normal callout check, Exim does a
25742 check for a &"random"& local part at the same domain. The local part is not
25743 really random &-- it is defined by the expansion of the option
25744 &%callout_random_local_part%&, which defaults to
25746 $primary_host_name-$tod_epoch-testing
25748 The idea here is to try to determine whether the remote host accepts all local
25749 parts without checking. If it does, there is no point in doing callouts for
25750 specific local parts. If the &"random"& check succeeds, the result is saved in
25751 a cache record, and used to force the current and subsequent callout checks to
25752 succeed without a connection being made, until the cache record expires.
25754 .vitem &*use_postmaster*&
25755 .cindex "callout" "sender for recipient check"
25756 This parameter applies to recipient callouts only. For example:
25758 deny !verify = recipient/callout=use_postmaster
25760 .cindex "&$qualify_domain$&"
25761 It causes a non-empty postmaster address to be used in the MAIL command when
25762 performing the callout for the recipient, and also for a &"random"& check if
25763 that is configured. The local part of the address is &`postmaster`& and the
25764 domain is the contents of &$qualify_domain$&.
25766 .vitem &*use_sender*&
25767 This option applies to recipient callouts only. For example:
25769 require verify = recipient/callout=use_sender
25771 It causes the message's actual sender address to be used in the MAIL
25772 command when performing the callout, instead of an empty address. There is no
25773 need to use this option unless you know that the called hosts make use of the
25774 sender when checking recipients. If used indiscriminately, it reduces the
25775 usefulness of callout caching.
25778 If you use any of the parameters that set a non-empty sender for the MAIL
25779 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
25780 &%use_sender%&), you should think about possible loops. Recipient checking is
25781 usually done between two hosts that are under the same management, and the host
25782 that receives the callouts is not normally configured to do callouts itself.
25783 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
25784 these circumstances.
25786 However, if you use a non-empty sender address for a callout to an arbitrary
25787 host, there is the likelihood that the remote host will itself initiate a
25788 callout check back to your host. As it is checking what appears to be a message
25789 sender, it is likely to use an empty address in MAIL, thus avoiding a
25790 callout loop. However, to be on the safe side it would be best to set up your
25791 own ACLs so that they do not do sender verification checks when the recipient
25792 is the address you use for header sender or postmaster callout checking.
25794 Another issue to think about when using non-empty senders for callouts is
25795 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
25796 by the sender/recipient combination; thus, for any given recipient, many more
25797 actual callouts are performed than when an empty sender or postmaster is used.
25802 .section "Callout caching" "SECTcallvercache"
25803 .cindex "hints database" "callout cache"
25804 .cindex "callout" "caching"
25805 .cindex "caching" "callout"
25806 Exim caches the results of callouts in order to reduce the amount of resources
25807 used, unless you specify the &%no_cache%& parameter with the &%callout%&
25808 option. A hints database called &"callout"& is used for the cache. Two
25809 different record types are used: one records the result of a callout check for
25810 a specific address, and the other records information that applies to the
25811 entire domain (for example, that it accepts the local part &'postmaster'&).
25813 When an original callout fails, a detailed SMTP error message is given about
25814 the failure. However, for subsequent failures use the cache data, this message
25817 The expiry times for negative and positive address cache records are
25818 independent, and can be set by the global options &%callout_negative_expire%&
25819 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
25821 If a host gives a negative response to an SMTP connection, or rejects any
25822 commands up to and including
25826 (but not including the MAIL command with a non-empty address),
25827 any callout attempt is bound to fail. Exim remembers such failures in a
25828 domain cache record, which it uses to fail callouts for the domain without
25829 making new connections, until the domain record times out. There are two
25830 separate expiry times for domain cache records:
25831 &%callout_domain_negative_expire%& (default 3h) and
25832 &%callout_domain_positive_expire%& (default 7d).
25834 Domain records expire when the negative expiry time is reached if callouts
25835 cannot be made for the domain, or if the postmaster check failed.
25836 Otherwise, they expire when the positive expiry time is reached. This
25837 ensures that, for example, a host that stops accepting &"random"& local parts
25838 will eventually be noticed.
25840 The callout caching mechanism is based on the domain of the address that is
25841 being tested. If the domain routes to several hosts, it is assumed that their
25842 behaviour will be the same.
25846 .section "Sender address verification reporting" "SECTsenaddver"
25847 .cindex "verifying" "suppressing error details"
25848 When sender verification fails in an ACL, the details of the failure are
25849 given as additional output lines before the 550 response to the relevant
25850 SMTP command (RCPT or DATA). For example, if sender callout is in use,
25853 MAIL FROM:<xyz@abc.example>
25855 RCPT TO:<pqr@def.example>
25856 550-Verification failed for <xyz@abc.example>
25857 550-Called: 192.168.34.43
25858 550-Sent: RCPT TO:<xyz@abc.example>
25859 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
25860 550 Sender verification failed
25862 If more than one RCPT command fails in the same way, the details are given
25863 only for the first of them. However, some administrators do not want to send
25864 out this much information. You can suppress the details by adding
25865 &`/no_details`& to the ACL statement that requests sender verification. For
25868 verify = sender/no_details
25871 .section "Redirection while verifying" "SECTredirwhilveri"
25872 .cindex "verifying" "redirection while"
25873 .cindex "address redirection" "while verifying"
25874 A dilemma arises when a local address is redirected by aliasing or forwarding
25875 during verification: should the generated addresses themselves be verified,
25876 or should the successful expansion of the original address be enough to verify
25877 it? By default, Exim takes the following pragmatic approach:
25880 When an incoming address is redirected to just one child address, verification
25881 continues with the child address, and if that fails to verify, the original
25882 verification also fails.
25884 When an incoming address is redirected to more than one child address,
25885 verification does not continue. A success result is returned.
25888 This seems the most reasonable behaviour for the common use of aliasing as a
25889 way of redirecting different local parts to the same mailbox. It means, for
25890 example, that a pair of alias entries of the form
25893 aw123: :fail: Gone away, no forwarding address
25895 work as expected, with both local parts causing verification failure. When a
25896 redirection generates more than one address, the behaviour is more like a
25897 mailing list, where the existence of the alias itself is sufficient for
25898 verification to succeed.
25900 It is possible, however, to change the default behaviour so that all successful
25901 redirections count as successful verifications, however many new addresses are
25902 generated. This is specified by the &%success_on_redirect%& verification
25903 option. For example:
25905 require verify = recipient/success_on_redirect/callout=10s
25907 In this example, verification succeeds if a router generates a new address, and
25908 the callout does not occur, because no address was routed to a remote host.
25913 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
25914 .cindex "CSA" "verifying"
25915 Client SMTP Authorization is a system that allows a site to advertise
25916 which machines are and are not permitted to send email. This is done by placing
25917 special SRV records in the DNS; these are looked up using the client's HELO
25918 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
25919 Authorization checks in Exim are performed by the ACL condition:
25923 This fails if the client is not authorized. If there is a DNS problem, or if no
25924 valid CSA SRV record is found, or if the client is authorized, the condition
25925 succeeds. These three cases can be distinguished using the expansion variable
25926 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
25927 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
25928 be likely to cause problems for legitimate email.
25930 The error messages produced by the CSA code include slightly more
25931 detail. If &$csa_status$& is &"defer"&, this may be because of problems
25932 looking up the CSA SRV record, or problems looking up the CSA target
25933 address record. There are four reasons for &$csa_status$& being &"fail"&:
25936 The client's host name is explicitly not authorized.
25938 The client's IP address does not match any of the CSA target IP addresses.
25940 The client's host name is authorized but it has no valid target IP addresses
25941 (for example, the target's addresses are IPv6 and the client is using IPv4).
25943 The client's host name has no CSA SRV record but a parent domain has asserted
25944 that all subdomains must be explicitly authorized.
25947 The &%csa%& verification condition can take an argument which is the domain to
25948 use for the DNS query. The default is:
25950 verify = csa/$sender_helo_name
25952 This implementation includes an extension to CSA. If the query domain
25953 is an address literal such as [192.0.2.95], or if it is a bare IP
25954 address, Exim searches for CSA SRV records in the reverse DNS as if
25955 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
25958 verify = csa/$sender_host_address
25960 In fact, this is the check that Exim performs if the client does not say HELO.
25961 This extension can be turned off by setting the main configuration option
25962 &%dns_csa_use_reverse%& to be false.
25964 If a CSA SRV record is not found for the domain itself, a search
25965 is performed through its parent domains for a record which might be
25966 making assertions about subdomains. The maximum depth of this search is limited
25967 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
25968 default. Exim does not look for CSA SRV records in a top level domain, so the
25969 default settings handle HELO domains as long as seven
25970 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
25971 of legitimate HELO domains.
25973 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
25974 direct SRV lookups, this is not sufficient because of the extra parent domain
25975 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
25976 addresses into lookups in the reverse DNS space. The result of a successful
25979 ${lookup dnsdb {csa=$sender_helo_name}}
25981 has two space-separated fields: an authorization code and a target host name.
25982 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
25983 authorization required but absent, or &"?"& for unknown.
25988 .section "Bounce address tag validation" "SECTverifyPRVS"
25989 .cindex "BATV" "verifying"
25990 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
25991 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
25992 Genuine incoming bounce messages should therefore always be addressed to
25993 recipients that have a valid tag. This scheme is a way of detecting unwanted
25994 bounce messages caused by sender address forgeries (often called &"collateral
25995 spam"&), because the recipients of such messages do not include valid tags.
25997 There are two expansion items to help with the implementation of the BATV
25998 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
25999 the original envelope sender address by using a simple shared key to add a hash
26000 of the address and some time-based randomizing information. The &%prvs%&
26001 expansion item creates a signed address, and the &%prvscheck%& expansion item
26002 checks one. The syntax of these expansion items is described in section
26003 &<<SECTexpansionitems>>&.
26005 As an example, suppose the secret per-address keys are stored in an MySQL
26006 database. A query to look up the key for an address could be defined as a macro
26009 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
26010 WHERE sender='${quote_mysql:$prvscheck_address}'\
26013 Suppose also that the senders who make use of BATV are defined by an address
26014 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
26017 # Bounces: drop unsigned addresses for BATV senders
26018 deny message = This address does not send an unsigned reverse path.
26020 recipients = +batv_senders
26022 # Bounces: In case of prvs-signed address, check signature.
26023 deny message = Invalid reverse path signature.
26025 condition = ${prvscheck {$local_part@$domain}\
26026 {PRVSCHECK_SQL}{1}}
26027 !condition = $prvscheck_result
26029 The first statement rejects recipients for bounce messages that are addressed
26030 to plain BATV sender addresses, because it is known that BATV senders do not
26031 send out messages with plain sender addresses. The second statement rejects
26032 recipients that are prvs-signed, but with invalid signatures (either because
26033 the key is wrong, or the signature has timed out).
26035 A non-prvs-signed address is not rejected by the second statement, because the
26036 &%prvscheck%& expansion yields an empty string if its first argument is not a
26037 prvs-signed address, thus causing the &%condition%& condition to be false. If
26038 the first argument is a syntactically valid prvs-signed address, the yield is
26039 the third string (in this case &"1"&), whether or not the cryptographic and
26040 timeout checks succeed. The &$prvscheck_result$& variable contains the result
26041 of the checks (empty for failure, &"1"& for success).
26044 There are two more issues you must consider when implementing prvs-signing.
26045 Firstly, you need to ensure that prvs-signed addresses are not blocked by your
26046 ACLs. A prvs-signed address contains a slash character, but the default Exim
26047 configuration contains this statement in the RCPT ACL:
26049 deny message = Restricted characters in address
26050 domains = +local_domains
26051 local_parts = ^[.] : ^.*[@%!/|]
26053 This is a conservative rule that blocks local parts that contain slashes. You
26054 should remove the slash in the last line.
26057 Secondly, you have to ensure that the routers accept prvs-signed addresses and
26058 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
26059 router to remove the signature with a configuration along these lines:
26063 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
26065 This works because, if the third argument of &%prvscheck%& is empty, the result
26066 of the expansion of a prvs-signed address is the decoded value of the original
26067 address. This router should probably be the first of your routers that handles
26070 To create BATV-signed addresses in the first place, a transport of this form
26073 external_smtp_batv:
26075 return_path = ${prvs {$return_path} \
26076 {${lookup mysql{SELECT \
26077 secret FROM batv_prvs WHERE \
26078 sender='${quote_mysql:$sender_address}'} \
26081 If no key can be found for the existing return path, no signing takes place.
26085 .section "Using an ACL to control relaying" "SECTrelaycontrol"
26086 .cindex "&ACL;" "relay control"
26087 .cindex "relaying" "control by ACL"
26088 .cindex "policy control" "relay control"
26089 An MTA is said to &'relay'& a message if it receives it from some host and
26090 delivers it directly to another host as a result of a remote address contained
26091 within it. Redirecting a local address via an alias or forward file and then
26092 passing the message on to another host is not relaying,
26093 .cindex "&""percent hack""&"
26094 but a redirection as a result of the &"percent hack"& is.
26096 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
26097 A host which is acting as a gateway or an MX backup is concerned with incoming
26098 relaying from arbitrary hosts to a specific set of domains. On the other hand,
26099 a host which is acting as a smart host for a number of clients is concerned
26100 with outgoing relaying from those clients to the Internet at large. Often the
26101 same host is fulfilling both functions,
26103 . as illustrated in the diagram below,
26105 but in principle these two kinds of relaying are entirely independent. What is
26106 not wanted is the transmission of mail from arbitrary remote hosts through your
26107 system to arbitrary domains.
26110 You can implement relay control by means of suitable statements in the ACL that
26111 runs for each RCPT command. For convenience, it is often easiest to use
26112 Exim's named list facility to define the domains and hosts involved. For
26113 example, suppose you want to do the following:
26116 Deliver a number of domains to mailboxes on the local host (or process them
26117 locally in some other way). Let's say these are &'my.dom1.example'& and
26118 &'my.dom2.example'&.
26120 Relay mail for a number of other domains for which you are the secondary MX.
26121 These might be &'friend1.example'& and &'friend2.example'&.
26123 Relay mail from the hosts on your local LAN, to whatever domains are involved.
26124 Suppose your LAN is 192.168.45.0/24.
26128 In the main part of the configuration, you put the following definitions:
26130 domainlist local_domains = my.dom1.example : my.dom2.example
26131 domainlist relay_domains = friend1.example : friend2.example
26132 hostlist relay_hosts = 192.168.45.0/24
26134 Now you can use these definitions in the ACL that is run for every RCPT
26138 accept domains = +local_domains : +relay_domains
26139 accept hosts = +relay_hosts
26141 The first statement accepts any RCPT command that contains an address in
26142 the local or relay domains. For any other domain, control passes to the second
26143 statement, which accepts the command only if it comes from one of the relay
26144 hosts. In practice, you will probably want to make your ACL more sophisticated
26145 than this, for example, by including sender and recipient verification. The
26146 default configuration includes a more comprehensive example, which is described
26147 in chapter &<<CHAPdefconfil>>&.
26151 .section "Checking a relay configuration" "SECTcheralcon"
26152 .cindex "relaying" "checking control of"
26153 You can check the relay characteristics of your configuration in the same way
26154 that you can test any ACL behaviour for an incoming SMTP connection, by using
26155 the &%-bh%& option to run a fake SMTP session with which you interact.
26157 For specifically testing for unwanted relaying, the host
26158 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
26159 host from the host on which Exim is running, using the normal telnet port, you
26160 will see a normal telnet connection message and then quite a long delay. Be
26161 patient. The remote host is making an SMTP connection back to your host, and
26162 trying a number of common probes to test for open relay vulnerability. The
26163 results of the tests will eventually appear on your terminal.
26168 . ////////////////////////////////////////////////////////////////////////////
26169 . ////////////////////////////////////////////////////////////////////////////
26171 .chapter "Content scanning at ACL time" "CHAPexiscan"
26172 .scindex IIDcosca "content scanning" "at ACL time"
26173 The extension of Exim to include content scanning at ACL time, formerly known
26174 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
26175 was integrated into the main source for Exim release 4.50, and Tom continues to
26176 maintain it. Most of the wording of this chapter is taken from Tom's
26179 It is also possible to scan the content of messages at other times. The
26180 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
26181 scanning after all the ACLs have run. A transport filter can be used to scan
26182 messages at delivery time (see the &%transport_filter%& option, described in
26183 chapter &<<CHAPtransportgeneric>>&).
26185 If you want to include the ACL-time content-scanning features when you compile
26186 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
26187 &_Local/Makefile_&. When you do that, the Exim binary is built with:
26190 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
26191 for all MIME parts for SMTP and non-SMTP messages, respectively.
26193 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
26194 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
26195 run at the end of message reception (the &%acl_smtp_data%& ACL).
26197 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
26198 of messages, or parts of messages, for debugging purposes.
26200 Additional expansion variables that are set in the new ACL and by the new
26203 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
26206 There is another content-scanning configuration option for &_Local/Makefile_&,
26207 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
26208 condition is compiled, in addition to all the other content-scanning features.
26210 Content-scanning is continually evolving, and new features are still being
26211 added. While such features are still unstable and liable to incompatible
26212 changes, they are made available in Exim by setting options whose names begin
26213 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
26214 this manual. You can find out about them by reading the file called
26215 &_doc/experimental.txt_&.
26217 All the content-scanning facilites work on a MBOX copy of the message that is
26218 temporarily created in a file called:
26220 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
26222 The &_.eml_& extension is a friendly hint to virus scanners that they can
26223 expect an MBOX-like structure inside that file. The file is created when the
26224 first content scanning facility is called. Subsequent calls to content
26225 scanning conditions open the same file again. The directory is recursively
26226 removed when the &%acl_smtp_data%& ACL has finished running, unless
26228 control = no_mbox_unspool
26230 has been encountered. When the MIME ACL decodes files, they are put into the
26231 same directory by default.
26235 .section "Scanning for viruses" "SECTscanvirus"
26236 .cindex "virus scanning"
26237 .cindex "content scanning" "for viruses"
26238 .cindex "content scanning" "the &%malware%& condition"
26239 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
26240 It supports a &"generic"& interface to scanners called via the shell, and
26241 specialized interfaces for &"daemon"& type virus scanners, which are resident
26242 in memory and thus are much faster.
26244 .cindex "&%av_scanner%&"
26245 You can set the &%av_scanner%& option in first part of the Exim configuration
26246 file to specify which scanner to use, together with any additional options that
26247 are needed. The basic syntax is as follows:
26249 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
26251 If you do not set &%av_scanner%&, it defaults to
26253 av_scanner = sophie:/var/run/sophie
26255 If the value of &%av_scanner%& starts with dollar character, it is expanded
26256 before use. The following scanner types are supported in this release:
26259 .vitem &%aveserver%&
26260 .cindex "virus scanners" "Kaspersky"
26261 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
26262 at &url(http://www.kaspersky.com). This scanner type takes one option,
26263 which is the path to the daemon's UNIX socket. The default is shown in this
26266 av_scanner = aveserver:/var/run/aveserver
26270 .cindex "virus scanners" "clamd"
26271 This daemon-type scanner is GPL and free. You can get it at
26272 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
26273 unpack MIME containers, so it used to be recommended to unpack MIME attachments
26274 in the MIME ACL. This no longer believed to be necessary. One option is
26275 required: either the path and name of a UNIX socket file, or a hostname or IP
26276 number, and a port, separated by space, as in the second of these examples:
26278 av_scanner = clamd:/opt/clamd/socket
26279 av_scanner = clamd:192.168.2.100 1234
26281 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
26282 contributing the code for this scanner.
26285 .cindex "virus scanners" "command line interface"
26286 This is the keyword for the generic command line scanner interface. It can be
26287 used to attach virus scanners that are invoked from the shell. This scanner
26288 type takes 3 mandatory options:
26291 The full path and name of the scanner binary, with all command line options,
26292 and a placeholder (&`%s`&) for the directory to scan.
26295 A regular expression to match against the STDOUT and STDERR output of the
26296 virus scanner. If the expression matches, a virus was found. You must make
26297 absolutely sure that this expression matches on &"virus found"&. This is called
26298 the &"trigger"& expression.
26301 Another regular expression, containing exactly one pair of parentheses, to
26302 match the name of the virus found in the scanners output. This is called the
26303 &"name"& expression.
26306 For example, Sophos Sweep reports a virus on a line like this:
26308 Virus 'W32/Magistr-B' found in file ./those.bat
26310 For the trigger expression, we can just match the word &"found"&. For the name
26311 expression, we want to extract the W32/Magistr-B string, so we can match for
26312 the single quotes left and right of it. Altogether, this makes the
26313 configuration setting:
26315 av_scanner = cmdline:\
26316 /path/to/sweep -all -rec -archive %s:\
26320 .cindex "virus scanners" "DrWeb"
26321 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
26322 argument, either a full path to a UNIX socket, or an IP address and port
26323 separated by white space, as in these examples:
26325 av_scanner = drweb:/var/run/drwebd.sock
26326 av_scanner = drweb:192.168.2.20 31337
26328 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
26329 is used. Thanks to Alex Miller for contributing the code for this scanner.
26332 .cindex "virus scanners" "F-Secure"
26333 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
26334 argument which is the path to a UNIX socket. For example:
26336 av_scanner = fsecure:/path/to/.fsav
26338 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
26339 Thelmen for contributing the code for this scanner.
26341 .vitem &%kavdaemon%&
26342 .cindex "virus scanners" "Kaspersky"
26343 This is the scanner daemon of Kaspersky Version 4. This version of the
26344 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
26345 scanner type takes one option, which is the path to the daemon's UNIX socket.
26348 av_scanner = kavdaemon:/opt/AVP/AvpCtl
26350 The default path is &_/var/run/AvpCtl_&.
26353 .cindex "virus scanners" "mksd"
26354 This is a daemon type scanner that is aimed mainly at Polish users, though some
26355 parts of documentation are now available in English. You can get it at
26356 &url(http://linux.mks.com.pl/). The only option for this scanner type is
26357 the maximum number of processes used simultaneously to scan the attachments,
26358 provided that the demime facility is employed and also provided that mksd has
26359 been run with at least the same number of child processes. For example:
26361 av_scanner = mksd:2
26363 You can safely omit this option (the default value is 1).
26366 .cindex "virus scanners" "Sophos and Sophie"
26367 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
26368 You can get Sophie at &url(http://www.vanja.com/tools/sophie/). The only
26369 option for this scanner type is the path to the UNIX socket that Sophie uses
26370 for client communication. For example:
26372 av_scanner = sophie:/tmp/sophie
26374 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
26378 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
26379 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
26382 The &%av_scanner%& option is expanded each time &%malware%& is called. This
26383 makes it possible to use different scanners. See further below for an example.
26384 The &%malware%& condition caches its results, so when you use it multiple times
26385 for the same message, the actual scanning process is only carried out once.
26386 However, using expandable items in &%av_scanner%& disables this caching, in
26387 which case each use of the &%malware%& condition causes a new scan of the
26390 The &%malware%& condition takes a right-hand argument that is expanded before
26391 use. It can then be one of
26394 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
26395 The condition succeeds if a virus was found, and fail otherwise. This is the
26398 &"false"& or &"0"&, in which case no scanning is done and the condition fails
26401 A regular expression, in which case the message is scanned for viruses. The
26402 condition succeeds if a virus is found and its name matches the regular
26403 expression. This allows you to take special actions on certain types of virus.
26406 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
26407 even if there is a problem with the virus scanner.
26409 .cindex "&$malware_name$&"
26410 When a virus is found, the condition sets up an expansion variable called
26411 &$malware_name$& that contains the name of the virus. You can use it in a
26412 &%message%& modifier that specifies the error returned to the sender, and/or in
26415 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
26416 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
26417 &%malware%& condition.
26419 Here is a very simple scanning example:
26421 deny message = This message contains malware ($malware_name)
26425 The next example accepts messages when there is a problem with the scanner:
26427 deny message = This message contains malware ($malware_name)
26429 malware = */defer_ok
26431 The next example shows how to use an ACL variable to scan with both sophie and
26432 aveserver. It assumes you have set:
26434 av_scanner = $acl_m0
26436 in the main Exim configuration.
26438 deny message = This message contains malware ($malware_name)
26439 set acl_m0 = sophie
26442 deny message = This message contains malware ($malware_name)
26443 set acl_m0 = aveserver
26448 .section "Scanning with SpamAssassin" "SECTscanspamass"
26449 .cindex "content scanning" "for spam"
26450 .cindex "spam scanning"
26451 .cindex "SpamAssassin" "scanning with"
26452 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
26453 score and a report for the message. You can get SpamAssassin at
26454 &url(http://www.spamassassin.org), or, if you have a working Perl
26455 installation, you can use CPAN by running:
26457 perl -MCPAN -e 'install Mail::SpamAssassin'
26459 SpamAssassin has its own set of configuration files. Please review its
26460 documentation to see how you can tweak it. The default installation should work
26463 .cindex "&%spamd_address%&"
26464 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
26465 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
26466 port for &%spamd%&, you must set the &%spamd_address%& option in the global
26467 part of the Exim configuration as follows (example):
26469 spamd_address = 192.168.99.45 387
26471 You do not need to set this option if you use the default. As of version 2.60,
26472 &%spamd%& also supports communication over UNIX sockets. If you want to use
26473 these, supply &%spamd_address%& with an absolute file name instead of a
26476 spamd_address = /var/run/spamd_socket
26478 You can have multiple &%spamd%& servers to improve scalability. These can
26479 reside on other hardware reachable over the network. To specify multiple
26480 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
26481 option, separated with colons:
26483 spamd_address = 192.168.2.10 783 : \
26484 192.168.2.11 783 : \
26487 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
26488 fashion. When a server fails to respond to the connection attempt, all other
26489 servers are tried until one succeeds. If no server responds, the &%spam%&
26492 &*Warning*&: It is not possible to use the UNIX socket connection method with
26493 multiple &%spamd%& servers.
26496 .section "Calling SpamAssassin from an Exim ACL"
26497 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
26499 deny message = This message was classified as SPAM
26502 The right-hand side of the &%spam%& condition specifies the username that
26503 SpamAssassin should scan for. If you do not want to scan for a particular user,
26504 but rather use the SpamAssassin system-wide default profile, you can scan for
26505 an unknown user, or simply use &"nobody"&. However, you must put something on
26506 the right-hand side.
26508 The username allows you to use per-domain or per-user antispam profiles. The
26509 right-hand side is expanded before being used, so you can put lookups or
26510 conditions there. When the right-hand side evaluates to &"0"& or &"false"&, no
26511 scanning is done and the condition fails immediately.
26513 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
26514 large ones may cause significant performance degredation. As most spam messages
26515 are quite small, it is recommended that you do not scan the big ones. For
26518 deny message = This message was classified as SPAM
26519 condition = ${if < {$message_size}{10K}}
26523 The &%spam%& condition returns true if the threshold specified in the user's
26524 SpamAssassin profile has been matched or exceeded. If you want to use the
26525 &%spam%& condition for its side effects (see the variables below), you can make
26526 it always return &"true"& by appending &`:true`& to the username.
26528 .cindex "spam scanning" "returned variables"
26529 When the &%spam%& condition is run, it sets up the following expansion
26533 .vitem &$spam_score$&
26534 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
26535 for inclusion in log or reject messages.
26537 .vitem &$spam_score_int$&
26538 The spam score of the message, multiplied by ten, as an integer value. For
26539 example &"34"& or &"305"&. This is useful for numeric comparisons in
26540 conditions. This variable is special; it is saved with the message, and written
26541 to Exim's spool file. This means that it can be used during the whole life of
26542 the message on your Exim system, in particular, in routers or transports during
26543 the later delivery phase.
26545 .vitem &$spam_bar$&
26546 A string consisting of a number of &"+"& or &"-"& characters, representing the
26547 integer part of the spam score value. A spam score of 4.4 would have a
26548 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
26549 headers, since MUAs can match on such strings.
26551 .vitem &$spam_report$&
26552 A multiline text table, containing the full SpamAssassin report for the
26553 message. Useful for inclusion in headers or reject messages.
26556 The &%spam%& condition caches its results. If you call it again with the same
26557 user name, it does not scan again, but rather returns the same values as
26560 The &%spam%& condition returns DEFER if there is any error while running the
26561 message through SpamAssassin. If you want to treat DEFER as FAIL (to pass on to
26562 the next ACL statement block), append &`/defer_ok`& to the right-hand side of
26563 the spam condition, like this:
26565 deny message = This message was classified as SPAM
26566 spam = joe/defer_ok
26568 This causes messages to be accepted even if there is a problem with &%spamd%&.
26570 Here is a longer, commented example of the use of the &%spam%&
26573 # put headers in all messages (no matter if spam or not)
26574 warn message = X-Spam-Score: $spam_score ($spam_bar)
26576 warn message = X-Spam-Report: $spam_report
26579 # add second subject line with *SPAM* marker when message
26580 # is over threshold
26581 warn message = Subject: *SPAM* $h_Subject:
26584 # reject spam at high scores (> 12)
26585 deny message = This message scored $spam_score spam points.
26587 condition = ${if >{$spam_score_int}{120}{1}{0}}
26592 .section "Scanning MIME parts" "SECTscanmimepart"
26593 .cindex "content scanning" "MIME parts"
26594 .cindex "MIME content scanning"
26595 .cindex "&%acl_smtp_mime%&"
26596 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
26597 each MIME part of an SMTP message, including multipart types, in the sequence
26598 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
26599 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
26600 options may both refer to the same ACL if you want the same processing in both
26603 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
26604 ACL in the case of an SMTP message, or just before a non-SMTP message is
26605 accepted. However, a MIME ACL is called only if the message contains a
26606 &'MIME-Version:'& header line. When a call to a MIME ACL does not yield
26607 &"accept"&, ACL processing is aborted and the appropriate result code is sent
26608 to the client. In the case of an SMTP message, the &%acl_smtp_data%& ACL is not
26609 called when this happens.
26611 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
26612 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
26613 condition to match against the raw MIME part. You can also use the
26614 &%mime_regex%& condition to match against the decoded MIME part (see section
26615 &<<SECTscanregex>>&).
26617 At the start of a MIME ACL, a number of variables are set from the header
26618 information for the relevant MIME part. These are described below. The contents
26619 of the MIME part are not by default decoded into a disk file except for MIME
26620 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
26621 part into a disk file, you can use the &%decode%& modifier. The general syntax
26624 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
26626 The right hand side is expanded before use. After expansion,
26630 &"0"& or &"false"&, in which case no decoding is done.
26632 The string &"default"&. In that case, the file is put in the temporary
26633 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
26634 a sequential file name consisting of the message id and a sequence number. The
26635 full path and name is available in &$mime_decoded_filename$& after decoding.
26637 A full path name starting with a slash. If the full name is an existing
26638 directory, it is used as a replacement for the default directory. The filename
26639 is then sequentially assigned. If the path does not exist, it is used as
26640 the full path and file name.
26642 If the string does not start with a slash, it is used as the
26643 filename, and the default path is then used.
26646 You can easily decode a file with its original, proposed filename using
26648 decode = $mime_filename
26650 However, you should keep in mind that &$mime_filename$& might contain
26651 anything. If you place files outside of the default path, they are not
26652 automatically unlinked.
26654 For RFC822 attachments (these are messages attached to messages, with a
26655 content-type of &"message/rfc822"&), the ACL is called again in the same manner
26656 as for the primary message, only that the &$mime_is_rfc822$& expansion
26657 variable is set (see below). Attached messages are always decoded to disk
26658 before being checked, and the files are unlinked once the check is done.
26660 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
26661 used to match regular expressions against raw and decoded MIME parts,
26662 respectively. They are described in section &<<SECTscanregex>>&.
26664 .cindex "MIME content scanning" "returned variables"
26665 The following list describes all expansion variables that are
26666 available in the MIME ACL:
26669 .vitem &$mime_boundary$&
26670 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
26671 have a boundary string, which is stored in this variable. If the current part
26672 has no boundary parameter in the &'Content-Type:'& header, this variable
26673 contains the empty string.
26675 .vitem &$mime_charset$&
26676 This variable contains the character set identifier, if one was found in the
26677 &'Content-Type:'& header. Examples for charset identifiers are:
26683 Please note that this value is not normalized, so you should do matches
26684 case-insensitively.
26686 .vitem &$mime_content_description$&
26687 This variable contains the normalized content of the &'Content-Description:'&
26688 header. It can contain a human-readable description of the parts content. Some
26689 implementations repeat the filename for attachments here, but they are usually
26690 only used for display purposes.
26692 .vitem &$mime_content_disposition$&
26693 This variable contains the normalized content of the &'Content-Disposition:'&
26694 header. You can expect strings like &"attachment"& or &"inline"& here.
26696 .vitem &$mime_content_id$&
26697 This variable contains the normalized content of the &'Content-ID:'& header.
26698 This is a unique ID that can be used to reference a part from another part.
26700 .vitem &$mime_content_size$&
26701 This variable is set only after the &%decode%& modifier (see above) has been
26702 successfully run. It contains the size of the decoded part in kilobytes. The
26703 size is always rounded up to full kilobytes, so only a completely empty part
26704 has a &$mime_content_size$& of zero.
26706 .vitem &$mime_content_transfer_encoding$&
26707 This variable contains the normalized content of the
26708 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
26709 type. Typical values are &"base64"& and &"quoted-printable"&.
26711 .vitem &$mime_content_type$&
26712 If the MIME part has a &'Content-Type:'& header, this variable contains its
26713 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
26714 are some examples of popular MIME types, as they may appear in this variable:
26718 application/octet-stream
26722 If the MIME part has no &'Content-Type:'& header, this variable contains the
26725 .vitem &$mime_decoded_filename$&
26726 This variable is set only after the &%decode%& modifier (see above) has been
26727 successfully run. It contains the full path and file name of the file
26728 containing the decoded data.
26733 .vitem &$mime_filename$&
26734 This is perhaps the most important of the MIME variables. It contains a
26735 proposed filename for an attachment, if one was found in either the
26736 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
26737 RFC2047 decoded, but no additional sanity checks are done. If no filename was
26738 found, this variable contains the empty string.
26740 .vitem &$mime_is_coverletter$&
26741 This variable attempts to differentiate the &"cover letter"& of an e-mail from
26742 attached data. It can be used to clamp down on flashy or unneccessarily encoded
26743 content in the cover letter, while not restricting attachments at all.
26745 The variable contains 1 (true) for a MIME part believed to be part of the
26746 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
26750 The outermost MIME part of a message is always a cover letter.
26753 If a multipart/alternative or multipart/related MIME part is a cover letter,
26754 so are all MIME subparts within that multipart.
26757 If any other multipart is a cover letter, the first subpart is a cover letter,
26758 and the rest are attachments.
26761 All parts contained within an attachment multipart are attachments.
26764 As an example, the following will ban &"HTML mail"& (including that sent with
26765 alternative plain text), while allowing HTML files to be attached. HTML
26766 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
26768 deny message = HTML mail is not accepted here
26769 !condition = $mime_is_rfc822
26770 condition = $mime_is_coverletter
26771 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
26773 .vitem &$mime_is_multipart$&
26774 This variable has the value 1 (true) when the current part has the main type
26775 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
26776 Since multipart entities only serve as containers for other parts, you may not
26777 want to carry out specific actions on them.
26779 .vitem &$mime_is_rfc822$&
26780 This variable has the value 1 (true) if the current part is not a part of the
26781 checked message itself, but part of an attached message. Attached message
26782 decoding is fully recursive.
26784 .vitem &$mime_part_count$&
26785 This variable is a counter that is raised for each processed MIME part. It
26786 starts at zero for the very first part (which is usually a multipart). The
26787 counter is per-message, so it is reset when processing RFC822 attachments (see
26788 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
26789 complete, so you can use it in the DATA ACL to determine the number of MIME
26790 parts of a message. For non-MIME messages, this variable contains the value -1.
26795 .section "Scanning with regular expressions" "SECTscanregex"
26796 .cindex "content scanning" "with regular expressions"
26797 .cindex "regular expressions" "content scanning with"
26798 You can specify your own custom regular expression matches on the full body of
26799 the message, or on individual MIME parts.
26801 The &%regex%& condition takes one or more regular expressions as arguments and
26802 matches them against the full message (when called in the DATA ACL) or a raw
26803 MIME part (when called in the MIME ACL). The &%regex%& condition matches
26804 linewise, with a maximum line length of 32K characters. That means you cannot
26805 have multiline matches with the &%regex%& condition.
26807 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
26808 to 32K of decoded content (the whole content at once, not linewise). If the
26809 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
26810 is decoded automatically when &%mime_regex%& is executed (using default path
26811 and filename values). If the decoded data is larger than 32K, only the first
26812 32K characters are checked.
26814 The regular expressions are passed as a colon-separated list. To include a
26815 literal colon, you must double it. Since the whole right-hand side string is
26816 expanded before being used, you must also escape dollar signs and backslashes
26817 with more backslashes, or use the &`\N`& facility to disable expansion.
26818 Here is a simple example that contains two regular expressions:
26820 deny message = contains blacklisted regex ($regex_match_string)
26821 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
26823 The conditions returns true if any one of the regular expressions matches. The
26824 &$regex_match_string$& expansion variable is then set up and contains the
26825 matching regular expression.
26827 &*Warning*&: With large messages, these conditions can be fairly
26833 .section "The demime condition" "SECTdemimecond"
26834 .cindex "content scanning" "MIME checking"
26835 .cindex "MIME content scanning"
26836 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
26837 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
26838 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
26839 ACL functionality, but provides no additional facilities. Please note that this
26840 condition is deprecated and kept only for backward compatibility. You must set
26841 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
26842 use the &%demime%& condition.
26844 The &%demime%& condition unpacks MIME containers in the message. It detects
26845 errors in MIME containers and can match file extensions found in the message
26846 against a list. Using this facility produces files containing the unpacked MIME
26847 parts of the message in the temporary scan directory. If you do antivirus
26848 scanning, it is recommened that you use the &%demime%& condition before the
26849 antivirus (&%malware%&) condition.
26851 On the right-hand side of the &%demime%& condition you can pass a
26852 colon-separated list of file extensions that it should match against. For
26855 deny message = Found blacklisted file attachment
26856 demime = vbs:com:bat:pif:prf:lnk
26858 If one of the file extensions is found, the condition is true, otherwise it is
26859 false. If there is a temporary error while demimeing (for example, &"disk
26860 full"&), the condition defers, and the message is temporarily rejected (unless
26861 the condition is on a &%warn%& verb).
26863 The right-hand side is expanded before being treated as a list, so you can have
26864 conditions and lookups there. If it expands to an empty string, &"false"&, or
26865 zero (&"0"&), no demimeing is done and the condition is false.
26867 The &%demime%& condition set the following variables:
26870 .vitem &$demime_errorlevel$&
26871 .cindex "&$demime_errorlevel$&"
26872 When an error is detected in a MIME container, this variable contains the
26873 severity of the error, as an integer number. The higher the value, the more
26874 severe the error (the current maximum value is 3). If this variable is unset or
26875 zero, no error occurred.
26877 .vitem &$demime_reason$&
26878 .cindex "&$demime_reason$&"
26879 When &$demime_errorlevel$& is greater than zero, this variable contains a
26880 human-readable text string describing the MIME error that occurred.
26884 .vitem &$found_extension$&
26885 .cindex "&$found_extension$&"
26886 When the &%demime%& condition is true, this variable contains the file
26887 extension it found.
26890 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
26891 the &%demime%& condition, and are not changed on subsequent calls.
26893 If you do not want to check for file extensions, but rather use the &%demime%&
26894 condition for unpacking or error checking purposes, pass &"*"& as the
26895 right-hand side value. Here is a more elaborate example of how to use this
26898 # Reject messages with serious MIME container errors
26899 deny message = Found MIME error ($demime_reason).
26901 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
26903 # Reject known virus spreading file extensions.
26904 # Accepting these is pretty much braindead.
26905 deny message = contains $found_extension file (blacklisted).
26906 demime = com:vbs:bat:pif:scr
26908 # Freeze .exe and .doc files. Postmaster can
26909 # examine them and eventually thaw them.
26910 deny log_message = Another $found_extension file.
26919 . ////////////////////////////////////////////////////////////////////////////
26920 . ////////////////////////////////////////////////////////////////////////////
26922 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
26923 "Local scan function"
26924 .scindex IIDlosca "&[local_scan()]& function" "description of"
26925 .cindex "customizing" "input scan using C function"
26926 .cindex "policy control" "by local scan function"
26927 In these days of email worms, viruses, and ever-increasing spam, some sites
26928 want to apply a lot of checking to messages before accepting them.
26930 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
26931 passing messages to external virus and spam scanning software. You can also do
26932 a certain amount in Exim itself through string expansions and the &%condition%&
26933 condition in the ACL that runs after the SMTP DATA command or the ACL for
26934 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
26936 To allow for further customization to a site's own requirements, there is the
26937 possibility of linking Exim with a private message scanning function, written
26938 in C. If you want to run code that is written in something other than C, you
26939 can of course use a little C stub to call it.
26941 The local scan function is run once for every incoming message, at the point
26942 when Exim is just about to accept the message.
26943 It can therefore be used to control non-SMTP messages from local processes as
26944 well as messages arriving via SMTP.
26946 Exim applies a timeout to calls of the local scan function, and there is an
26947 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
26948 Zero means &"no timeout"&.
26949 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
26950 before calling the local scan function, so that the most common types of crash
26951 are caught. If the timeout is exceeded or one of those signals is caught, the
26952 incoming message is rejected with a temporary error if it is an SMTP message.
26953 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
26954 code. The incident is logged on the main and reject logs.
26958 .section "Building Exim to use a local scan function"
26959 .cindex "&[local_scan()]& function" "building Exim to use"
26960 To make use of the local scan function feature, you must tell Exim where your
26961 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
26962 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
26963 directory, so you might set
26965 LOCAL_SCAN_SOURCE=Local/local_scan.c
26967 for example. The function must be called &[local_scan()]&. It is called by
26968 Exim after it has received a message, when the success return code is about to
26969 be sent. This is after all the ACLs have been run. The return code from your
26970 function controls whether the message is actually accepted or not. There is a
26971 commented template function (that just accepts the message) in the file
26972 _src/local_scan.c_.
26974 If you want to make use of Exim's run time configuration file to set options
26975 for your &[local_scan()]& function, you must also set
26977 LOCAL_SCAN_HAS_OPTIONS=yes
26979 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
26984 .section "API for local_scan()" "SECTapiforloc"
26985 .cindex "&[local_scan()]& function" "API description"
26986 You must include this line near the start of your code:
26988 #include "local_scan.h"
26990 This header file defines a number of variables and other values, and the
26991 prototype for the function itself. Exim is coded to use unsigned char values
26992 almost exclusively, and one of the things this header defines is a shorthand
26993 for &`unsigned char`& called &`uschar`&.
26994 It also contains the following macro definitions, to simplify casting character
26995 strings and pointers to character strings:
26997 #define CS (char *)
26998 #define CCS (const char *)
26999 #define CSS (char **)
27000 #define US (unsigned char *)
27001 #define CUS (const unsigned char *)
27002 #define USS (unsigned char **)
27004 The function prototype for &[local_scan()]& is:
27006 extern int local_scan(int fd, uschar **return_text);
27008 The arguments are as follows:
27011 &%fd%& is a file descriptor for the file that contains the body of the message
27012 (the -D file). The file is open for reading and writing, but updating it is not
27013 recommended. &*Warning*&: You must &'not'& close this file descriptor.
27015 The descriptor is positioned at character 19 of the file, which is the first
27016 character of the body itself, because the first 19 characters are the message
27017 id followed by &`-D`& and a newline. If you rewind the file, you should use the
27018 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
27019 case this changes in some future version.
27021 &%return_text%& is an address which you can use to return a pointer to a text
27022 string at the end of the function. The value it points to on entry is NULL.
27025 The function must return an &%int%& value which is one of the following macros:
27028 .vitem &`LOCAL_SCAN_ACCEPT`&
27029 .cindex "&$local_scan_data$&"
27030 The message is accepted. If you pass back a string of text, it is saved with
27031 the message, and made available in the variable &$local_scan_data$&. No
27032 newlines are permitted (if there are any, they are turned into spaces) and the
27033 maximum length of text is 1000 characters.
27035 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
27036 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
27037 queued without immediate delivery, and is frozen.
27039 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
27040 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
27041 queued without immediate delivery.
27043 .vitem &`LOCAL_SCAN_REJECT`&
27044 The message is rejected; the returned text is used as an error message which is
27045 passed back to the sender and which is also logged. Newlines are permitted &--
27046 they cause a multiline response for SMTP rejections, but are converted to
27047 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
27050 .vitem &`LOCAL_SCAN_TEMPREJECT`&
27051 The message is temporarily rejected; the returned text is used as an error
27052 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
27055 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
27056 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
27057 message is not written to the reject log. It has the effect of unsetting the
27058 &%rejected_header%& log selector for just this rejection. If
27059 &%rejected_header%& is already unset (see the discussion of the
27060 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
27061 same as LOCAL_SCAN_REJECT.
27063 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
27064 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
27065 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
27068 If the message is not being received by interactive SMTP, rejections are
27069 reported by writing to &%stderr%& or by sending an email, as configured by the
27070 &%-oe%& command line options.
27074 .section "Configuration options for local_scan()" "SECTconoptloc"
27075 .cindex "&[local_scan()]& function" "configuration options"
27076 It is possible to have option settings in the main configuration file
27077 that set values in static variables in the &[local_scan()]& module. If you
27078 want to do this, you must have the line
27080 LOCAL_SCAN_HAS_OPTIONS=yes
27082 in your &_Local/Makefile_& when you build Exim. (This line is in
27083 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
27084 file, you must define static variables to hold the option values, and a table
27087 The table must be a vector called &%local_scan_options%&, of type
27088 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
27089 and a pointer to the variable that holds the value. The entries must appear in
27090 alphabetical order. Following &%local_scan_options%& you must also define a
27091 variable called &%local_scan_options_count%& that contains the number of
27092 entries in the table. Here is a short example, showing two kinds of option:
27094 static int my_integer_option = 42;
27095 static uschar *my_string_option = US"a default string";
27097 optionlist local_scan_options[] = {
27098 { "my_integer", opt_int, &my_integer_option },
27099 { "my_string", opt_stringptr, &my_string_option }
27102 int local_scan_options_count =
27103 sizeof(local_scan_options)/sizeof(optionlist);
27105 The values of the variables can now be changed from Exim's runtime
27106 configuration file by including a local scan section as in this example:
27110 my_string = some string of text...
27112 The available types of option data are as follows:
27115 .vitem &*opt_bool*&
27116 This specifies a boolean (true/false) option. The address should point to a
27117 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
27118 that are defined as &"1"& and &"0"&, respectively. If you want to detect
27119 whether such a variable has been set at all, you can initialize it to
27120 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
27123 .vitem &*opt_fixed*&
27124 This specifies a fixed point number, such as is used for load averages.
27125 The address should point to a variable of type &`int`&. The value is stored
27126 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
27129 This specifies an integer; the address should point to a variable of type
27130 &`int`&. The value may be specified in any of the integer formats accepted by
27133 .vitem &*opt_mkint*&
27134 This is the same as &%opt_int%&, except that when such a value is output in a
27135 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
27136 printed with the suffix K or M.
27138 .vitem &*opt_octint*&
27139 This also specifies an integer, but the value is always interpeted as an
27140 octal integer, whether or not it starts with the digit zero, and it is
27141 always output in octal.
27143 .vitem &*opt_stringptr*&
27144 This specifies a string value; the address must be a pointer to a
27145 variable that points to a string (for example, of type &`uschar *`&).
27147 .vitem &*opt_time*&
27148 This specifies a time interval value. The address must point to a variable of
27149 type &`int`&. The value that is placed there is a number of seconds.
27152 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
27153 out the values of all the &[local_scan()]& options.
27157 .section "Available Exim variables"
27158 .cindex "&[local_scan()]& function" "available Exim variables"
27159 The header &_local_scan.h_& gives you access to a number of C variables. These
27160 are the only ones that are guaranteed to be maintained from release to release.
27161 Note, however, that you can obtain the value of any Exim variable by calling
27162 &'expand_string()'&. The exported variables are as follows:
27165 .vitem &*unsigned&~int&~debug_selector*&
27166 This variable is set to zero when no debugging is taking place. Otherwise, it
27167 is a bitmap of debugging selectors. Two bits are identified for use in
27168 &[local_scan()]&; they are defined as macros:
27171 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
27172 testing option that is not privileged &-- any caller may set it. All the
27173 other selector bits can be set only by admin users.
27176 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
27177 by the &`+local_scan`& debug selector. It is not included in the default set
27181 Thus, to write to the debugging output only when &`+local_scan`& has been
27182 selected, you should use code like this:
27184 if ((debug_selector & D_local_scan) != 0)
27185 debug_printf("xxx", ...);
27187 .vitem &*uschar&~*expand_string_message*&
27188 After a failing call to &'expand_string()'& (returned value NULL), the
27189 variable &%expand_string_message%& contains the error message, zero-terminated.
27191 .vitem &*header_line&~*header_list*&
27192 A pointer to a chain of header lines. The &%header_line%& structure is
27195 .vitem &*header_line&~*header_last*&
27196 A pointer to the last of the header lines.
27198 .vitem &*uschar&~*headers_charset*&
27199 The value of the &%headers_charset%& configuration option.
27201 .vitem &*BOOL&~host_checking*&
27202 This variable is TRUE during a host checking session that is initiated by the
27203 &%-bh%& command line option.
27205 .vitem &*uschar&~*interface_address*&
27206 The IP address of the interface that received the message, as a string. This
27207 is NULL for locally submitted messages.
27209 .vitem &*int&~interface_port*&
27210 The port on which this message was received.
27212 .vitem &*uschar&~*message_id*&
27213 This variable contains Exim's message id for the incoming message (the value of
27214 &$message_exim_id$&) as a zero-terminated string.
27216 .vitem &*uschar&~*received_protocol*&
27217 The name of the protocol by which the message was received.
27219 .vitem &*int&~recipients_count*&
27220 The number of accepted recipients.
27222 .vitem &*recipient_item&~*recipients_list*&
27223 .cindex "recipient" "adding in local scan"
27224 .cindex "recipient" "removing in local scan"
27225 The list of accepted recipients, held in a vector of length
27226 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
27227 can add additional recipients by calling &'receive_add_recipient()'& (see
27228 below). You can delete recipients by removing them from the vector and adusting
27229 the value in &%recipients_count%&. In particular, by setting
27230 &%recipients_count%& to zero you remove all recipients. If you then return the
27231 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
27232 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
27233 and then call &'receive_add_recipient()'& as often as needed.
27235 .vitem &*uschar&~*sender_address*&
27236 The envelope sender address. For bounce messages this is the empty string.
27238 .vitem &*uschar&~*sender_host_address*&
27239 The IP address of the sending host, as a string. This is NULL for
27240 locally-submitted messages.
27242 .vitem &*uschar&~*sender_host_authenticated*&
27243 The name of the authentication mechanism that was used, or NULL if the message
27244 was not received over an authenticated SMTP connection.
27246 .vitem &*uschar&~*sender_host_name*&
27247 The name of the sending host, if known.
27249 .vitem &*int&~sender_host_port*&
27250 The port on the sending host.
27252 .vitem &*BOOL&~smtp_input*&
27253 This variable is TRUE for all SMTP input, including BSMTP.
27255 .vitem &*BOOL&~smtp_batched_input*&
27256 This variable is TRUE for BSMTP input.
27258 .vitem &*int&~store_pool*&
27259 The contents of this variable control which pool of memory is used for new
27260 requests. See section &<<SECTmemhanloc>>& for details.
27264 .section "Structure of header lines"
27265 The &%header_line%& structure contains the members listed below.
27266 You can add additional header lines by calling the &'header_add()'& function
27267 (see below). You can cause header lines to be ignored (deleted) by setting
27272 .vitem &*struct&~header_line&~*next*&
27273 A pointer to the next header line, or NULL for the last line.
27275 .vitem &*int&~type*&
27276 A code identifying certain headers that Exim recognizes. The codes are printing
27277 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
27278 Notice in particular that any header line whose type is * is not transmitted
27279 with the message. This flagging is used for header lines that have been
27280 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
27281 lines.) Effectively, * means &"deleted"&.
27283 .vitem &*int&~slen*&
27284 The number of characters in the header line, including the terminating and any
27287 .vitem &*uschar&~*text*&
27288 A pointer to the text of the header. It always ends with a newline, followed by
27289 a zero byte. Internal newlines are preserved.
27294 .section "Structure of recipient items"
27295 The &%recipient_item%& structure contains these members:
27298 .vitem &*uschar&~*address*&
27299 This is a pointer to the recipient address as it was received.
27301 .vitem &*int&~pno*&
27302 This is used in later Exim processing when top level addresses are created by
27303 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
27304 and must always contain -1 at this stage.
27306 .vitem &*uschar&~*errors_to*&
27307 If this value is not NULL, bounce messages caused by failing to deliver to the
27308 recipient are sent to the address it contains. In other words, it overrides the
27309 envelope sender for this one recipient. (Compare the &%errors_to%& generic
27310 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
27311 an unqualified address, Exim qualifies it using the domain from
27312 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
27313 is NULL for all recipients.
27318 .section "Available Exim functions"
27319 .cindex "&[local_scan()]& function" "available Exim functions"
27320 The header &_local_scan.h_& gives you access to a number of Exim functions.
27321 These are the only ones that are guaranteed to be maintained from release to
27325 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
27326 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
27328 This function creates a child process that runs the command specified by
27329 &%argv%&. The environment for the process is specified by &%envp%&, which can
27330 be NULL if no environment variables are to be passed. A new umask is supplied
27331 for the process in &%newumask%&.
27333 Pipes to the standard input and output of the new process are set up
27334 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
27335 standard error is cloned to the standard output. If there are any file
27336 descriptors &"in the way"& in the new process, they are closed. If the final
27337 argument is TRUE, the new process is made into a process group leader.
27339 The function returns the pid of the new process, or -1 if things go wrong.
27341 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
27342 This function waits for a child process to terminate, or for a timeout (in
27343 seconds) to expire. A timeout value of zero means wait as long as it takes. The
27344 return value is as follows:
27349 The process terminated by a normal exit and the value is the process
27355 The process was terminated by a signal and the value is the negation of the
27361 The process timed out.
27365 The was some other error in wait(); &%errno%& is still set.
27368 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
27369 This function provide you with a means of submitting a new message to
27370 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
27371 want, but this packages it all up for you.) The function creates a pipe,
27372 forks a subprocess that is running
27374 exim -t -oem -oi -f <>
27376 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
27377 that is connected to the standard input. The yield of the function is the PID
27378 of the subprocess. You can then write a message to the file descriptor, with
27379 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
27381 When you have finished, call &'child_close()'& to wait for the process to
27382 finish and to collect its ending status. A timeout value of zero is usually
27383 fine in this circumstance. Unless you have made a mistake with the recipient
27384 addresses, you should get a return code of zero.
27388 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
27389 *sender_authentication)*&
27390 This function is a more sophisticated version of &'child_open()'&. The command
27393 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
27395 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
27399 .vitem &*void&~debug_printf(char&~*,&~...)*&
27400 This is Exim's debugging function, with arguments as for &'(printf()'&. The
27401 output is written to the standard error stream. If no debugging is selected,
27402 calls to &'debug_printf()'& have no effect. Normally, you should make calls
27403 conditional on the &`local_scan`& debug selector by coding like this:
27405 if ((debug_selector & D_local_scan) != 0)
27406 debug_printf("xxx", ...);
27409 .vitem &*uschar&~*expand_string(uschar&~*string)*&
27410 This is an interface to Exim's string expansion code. The return value is the
27411 expanded string, or NULL if there was an expansion failure.
27412 The C variable &%expand_string_message%& contains an error message after an
27413 expansion failure. If expansion does not change the string, the return value is
27414 the pointer to the input string. Otherwise, the return value points to a new
27415 block of memory that was obtained by a call to &'store_get()'&. See section
27416 &<<SECTmemhanloc>>& below for a discussion of memory handling.
27418 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
27419 This function allows you to an add additional header line at the end of the
27420 existing ones. The first argument is the type, and should normally be a space
27421 character. The second argument is a format string and any number of
27422 substitution arguments as for &[sprintf()]&. You may include internal newlines
27423 if you want, and you must ensure that the string ends with a newline.
27425 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
27426 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
27427 This function adds a new header line at a specified point in the header
27428 chain. The header itself is specified as for &'header_add()'&.
27430 If &%name%& is NULL, the new header is added at the end of the chain if
27431 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
27432 NULL, the header lines are searched for the first non-deleted header that
27433 matches the name. If one is found, the new header is added before it if
27434 &%after%& is false. If &%after%& is true, the new header is added after the
27435 found header and any adjacent subsequent ones with the same name (even if
27436 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
27437 option controls where the header is added. If it is true, addition is at the
27438 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
27439 headers, or at the top if there are no &'Received:'& headers, you could use
27441 header_add_at_position(TRUE, US"Received", TRUE,
27442 ' ', "X-xxx: ...");
27444 Normally, there is always at least one non-deleted &'Received:'& header, but
27445 there may not be if &%received_header_text%& expands to an empty string.
27448 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
27449 This function removes header lines. If &%occurrence%& is zero or negative, all
27450 occurrences of the header are removed. If occurrence is greater than zero, that
27451 particular instance of the header is removed. If no header(s) can be found that
27452 match the specification, the function does nothing.
27455 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
27456 int&~length,&~BOOL&~notdel)*&"
27457 This function tests whether the given header has the given name. It is not just
27458 a string comparison, because white space is permitted between the name and the
27459 colon. If the &%notdel%& argument is true, a false return is forced for all
27460 &"deleted"& headers; otherwise they are not treated specially. For example:
27462 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
27464 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
27465 .cindex "base64 encoding" "functions for &[local_scan()]& use"
27466 This function base64-encodes a string, which is passed by address and length.
27467 The text may contain bytes of any value, including zero. The result is passed
27468 back in dynamic memory that is obtained by calling &'store_get()'&. It is
27471 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
27472 This function decodes a base64-encoded string. Its arguments are a
27473 zero-terminated base64-encoded string and the address of a variable that is set
27474 to point to the result, which is in dynamic memory. The length of the decoded
27475 string is the yield of the function. If the input is invalid base64 data, the
27476 yield is -1. A zero byte is added to the end of the output string to make it
27477 easy to interpret as a C string (assuming it contains no zeros of its own). The
27478 added zero byte is not included in the returned count.
27480 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
27481 This function checks for a match in a domain list. Domains are always
27482 matched caselessly. The return value is one of the following:
27484 &`OK `& match succeeded
27485 &`FAIL `& match failed
27486 &`DEFER `& match deferred
27488 DEFER is usually caused by some kind of lookup defer, such as the
27489 inability to contact a database.
27491 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
27493 This function checks for a match in a local part list. The third argument
27494 controls case-sensitivity. The return values are as for
27495 &'lss_match_domain()'&.
27497 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
27499 This function checks for a match in an address list. The third argument
27500 controls the case-sensitivity of the local part match. The domain is always
27501 matched caselessly. The return values are as for &'lss_match_domain()'&.
27503 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
27505 This function checks for a match in a host list. The most common usage is
27508 lss_match_host(sender_host_name, sender_host_address, ...)
27510 .cindex "&$sender_host_address$&"
27511 An empty address field matches an empty item in the host list. If the host name
27512 is NULL, the name corresponding to &$sender_host_address$& is automatically
27513 looked up if a host name is required to match an item in the list. The return
27514 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
27515 returns ERROR in the case when it had to look up a host name, but the lookup
27518 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
27520 This function writes to Exim's log files. The first argument should be zero (it
27521 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
27522 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
27523 them. It specifies to which log or logs the message is written. The remaining
27524 arguments are a format and relevant insertion arguments. The string should not
27525 contain any newlines, not even at the end.
27528 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
27529 This function adds an additional recipient to the message. The first argument
27530 is the recipient address. If it is unqualified (has no domain), it is qualified
27531 with the &%qualify_recipient%& domain. The second argument must always be -1.
27533 This function does not allow you to specify a private &%errors_to%& address (as
27534 described with the structure of &%recipient_item%& above), because it pre-dates
27535 the addition of that field to the structure. However, it is easy to add such a
27536 value afterwards. For example:
27538 receive_add_recipient(US"monitor@mydom.example", -1);
27539 recipients_list[recipients_count-1].errors_to =
27540 US"postmaster@mydom.example";
27543 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
27544 This is a convenience function to remove a named recipient from the list of
27545 recipients. It returns true if a recipient was removed, and false if no
27546 matching recipient could be found. The argument must be a complete email
27553 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
27554 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
27555 This function decodes strings that are encoded according to RFC 2047. Typically
27556 these are the contents of header lines. First, each &"encoded word"& is decoded
27557 from the Q or B encoding into a byte-string. Then, if provided with the name of
27558 a charset encoding, and if the &[iconv()]& function is available, an attempt is
27559 made to translate the result to the named character set. If this fails, the
27560 binary string is returned with an error message.
27562 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
27563 maximum MIME word length is enforced. The third argument is the target
27564 encoding, or NULL if no translation is wanted.
27566 .cindex "binary zero" "in RFC 2047 decoding"
27567 .cindex "RFC 2047" "binary zero in"
27568 If a binary zero is encountered in the decoded string, it is replaced by the
27569 contents of the &%zeroval%& argument. For use with Exim headers, the value must
27570 not be 0 because header lines are handled as zero-terminated strings.
27572 The function returns the result of processing the string, zero-terminated; if
27573 &%lenptr%& is not NULL, the length of the result is set in the variable to
27574 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
27576 If an error is encountered, the function returns NULL and uses the &%error%&
27577 argument to return an error message. The variable pointed to by &%error%& is
27578 set to NULL if there is no error; it may be set non-NULL even when the function
27579 returns a non-NULL value if decoding was successful, but there was a problem
27583 .vitem &*int&~smtp_fflush(void)*&
27584 This function is used in conjunction with &'smtp_printf()'&, as described
27587 .vitem &*void&~smtp_printf(char&~*,&~...)*&
27588 The arguments of this function are like &[printf()]&; it writes to the SMTP
27589 output stream. You should use this function only when there is an SMTP output
27590 stream, that is, when the incoming message is being received via interactive
27591 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
27592 is FALSE. If you want to test for an incoming message from another host (as
27593 opposed to a local process that used the &%-bs%& command line option), you can
27594 test the value of &%sender_host_address%&, which is non-NULL when a remote host
27597 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
27598 output function, so it can be used for all forms of SMTP connection.
27600 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
27601 must start with an appropriate response code: 550 if you are going to return
27602 LOCAL_SCAN_REJECT, 451 if you are going to return
27603 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
27604 initial lines of a multi-line response, the code must be followed by a hyphen
27605 to indicate that the line is not the final response line. You must also ensure
27606 that the lines you write terminate with CRLF. For example:
27608 smtp_printf("550-this is some extra info\r\n");
27609 return LOCAL_SCAN_REJECT;
27611 Note that you can also create multi-line responses by including newlines in
27612 the data returned via the &%return_text%& argument. The added value of using
27613 &'smtp_printf()'& is that, for instance, you could introduce delays between
27614 multiple output lines.
27616 The &'smtp_printf()'& function does not return any error indication, because it
27617 does not automatically flush pending output, and therefore does not test
27618 the state of the stream. (In the main code of Exim, flushing and error
27619 detection is done when Exim is ready for the next SMTP input command.) If
27620 you want to flush the output and check for an error (for example, the
27621 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
27622 arguments. It flushes the output stream, and returns a non-zero value if there
27625 .vitem &*void&~*store_get(int)*&
27626 This function accesses Exim's internal store (memory) manager. It gets a new
27627 chunk of memory whose size is given by the argument. Exim bombs out if it ever
27628 runs out of memory. See the next section for a discussion of memory handling.
27630 .vitem &*void&~*store_get_perm(int)*&
27631 This function is like &'store_get()'&, but it always gets memory from the
27632 permanent pool. See the next section for a discussion of memory handling.
27634 .vitem &*uschar&~*string_copy(uschar&~*string)*&
27637 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
27640 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
27641 These three functions create strings using Exim's dynamic memory facilities.
27642 The first makes a copy of an entire string. The second copies up to a maximum
27643 number of characters, indicated by the second argument. The third uses a format
27644 and insertion arguments to create a new string. In each case, the result is a
27645 pointer to a new string in the current memory pool. See the next section for
27651 .section "More about Exim's memory handling" "SECTmemhanloc"
27652 .cindex "&[local_scan()]& function" "memory handling"
27653 No function is provided for freeing memory, because that is never needed.
27654 The dynamic memory that Exim uses when receiving a message is automatically
27655 recycled if another message is received by the same process (this applies only
27656 to incoming SMTP connections &-- other input methods can supply only one
27657 message at a time). After receiving the last message, a reception process
27660 Because it is recycled, the normal dynamic memory cannot be used for holding
27661 data that must be preserved over a number of incoming messages on the same SMTP
27662 connection. However, Exim in fact uses two pools of dynamic memory; the second
27663 one is not recycled, and can be used for this purpose.
27665 If you want to allocate memory that remains available for subsequent messages
27666 in the same SMTP connection, you should set
27668 store_pool = POOL_PERM
27670 before calling the function that does the allocation. There is no need to
27671 restore the value if you do not need to; however, if you do want to revert to
27672 the normal pool, you can either restore the previous value of &%store_pool%& or
27673 set it explicitly to POOL_MAIN.
27675 The pool setting applies to all functions that get dynamic memory, including
27676 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
27677 There is also a convenience function called &'store_get_perm()'& that gets a
27678 block of memory from the permanent pool while preserving the value of
27685 . ////////////////////////////////////////////////////////////////////////////
27686 . ////////////////////////////////////////////////////////////////////////////
27688 .chapter "System-wide message filtering" "CHAPsystemfilter"
27689 .scindex IIDsysfil1 "filter" "system filter"
27690 .scindex IIDsysfil2 "filtering all mail"
27691 .scindex IIDsysfil3 "system filter"
27692 The previous chapters (on ACLs and the local scan function) describe checks
27693 that can be applied to messages before they are accepted by a host. There is
27694 also a mechanism for checking messages once they have been received, but before
27695 they are delivered. This is called the &'system filter'&.
27697 The system filter operates in a similar manner to users' filter files, but it
27698 is run just once per message (however many recipients the message has).
27699 It should not normally be used as a substitute for routing, because &%deliver%&
27700 commands in a system router provide new envelope recipient addresses.
27701 The system filter must be an Exim filter. It cannot be a Sieve filter.
27703 The system filter is run at the start of a delivery attempt, before any routing
27704 is done. If a message fails to be completely delivered at the first attempt,
27705 the system filter is run again at the start of every retry.
27706 If you want your filter to do something only once per message, you can make use
27707 of the &%first_delivery%& condition in an &%if%& command in the filter to
27708 prevent it happening on retries.
27710 .cindex "&$domain$&"
27711 .cindex "&$local_part$&"
27712 &*Warning*&: Because the system filter runs just once, variables that are
27713 specific to individual recipient addresses, such as &$local_part$& and
27714 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
27715 you want to run a centrally-specified filter for each recipient address
27716 independently, you can do so by setting up a suitable &(redirect)& router, as
27717 described in section &<<SECTperaddfil>>& below.
27720 .section "Specifying a system filter"
27721 .cindex "uid (user id)" "system filter"
27722 .cindex "gid (group id)" "system filter"
27723 The name of the file that contains the system filter must be specified by
27724 setting &%system_filter%&. If you want the filter to run under a uid and gid
27725 other than root, you must also set &%system_filter_user%& and
27726 &%system_filter_group%& as appropriate. For example:
27728 system_filter = /etc/mail/exim.filter
27729 system_filter_user = exim
27731 If a system filter generates any deliveries directly to files or pipes (via the
27732 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
27733 specified by setting &%system_filter_file_transport%& and
27734 &%system_filter_pipe_transport%&, respectively. Similarly,
27735 &%system_filter_reply_transport%& must be set to handle any messages generated
27736 by the &%reply%& command.
27739 .section "Testing a system filter"
27740 You can run simple tests of a system filter in the same way as for a user
27741 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
27742 are permitted only in system filters are recognized.
27744 If you want to test the combined effect of a system filter and a user filter,
27745 you can use both &%-bF%& and &%-bf%& on the same command line.
27749 .section "Contents of a system filter"
27750 The language used to specify system filters is the same as for users' filter
27751 files. It is described in the separate end-user document &'Exim's interface to
27752 mail filtering'&. However, there are some additional features that are
27753 available only in system filters; these are described in subsequent sections.
27754 If they are encountered in a user's filter file or when testing with &%-bf%&,
27757 .cindex "frozen messages" "manual thaw; testing in filter"
27758 There are two special conditions which, though available in users' filter
27759 files, are designed for use in system filters. The condition &%first_delivery%&
27760 is true only for the first attempt at delivering a message, and
27761 &%manually_thawed%& is true only if the message has been frozen, and
27762 subsequently thawed by an admin user. An explicit forced delivery counts as a
27763 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
27765 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
27766 specify an &"unseen"& (non-significant) delivery, and that delivery does not
27767 succeed, it will not be tried again.
27768 If you want Exim to retry an unseen delivery until it succeeds, you should
27769 arrange to set it up every time the filter runs.
27771 When a system filter finishes running, the values of the variables &$n0$& &--
27772 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
27773 users' filter files. Thus a system filter can, for example, set up &"scores"&
27774 to which users' filter files can refer.
27778 .section "Additional variable for system filters"
27779 .cindex "&$recipients$&"
27780 The expansion variable &$recipients$&, containing a list of all the recipients
27781 of the message (separated by commas and white space), is available in system
27782 filters. It is not available in users' filters for privacy reasons.
27786 .section "Defer, freeze, and fail commands for system filters"
27787 .cindex "freezing messages"
27788 .cindex "message" "freezing"
27789 .cindex "message" "forced failure"
27790 .cindex "&%fail%&" "in system filter"
27791 .cindex "&%freeze%& in system filter"
27792 .cindex "&%defer%& in system filter"
27793 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
27794 always available in system filters, but are not normally enabled in users'
27795 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
27796 for the &(redirect)& router.) These commands can optionally be followed by the
27797 word &%text%& and a string containing an error message, for example:
27799 fail text "this message looks like spam to me"
27801 The keyword &%text%& is optional if the next character is a double quote.
27803 The &%defer%& command defers delivery of the original recipients of the
27804 message. The &%fail%& command causes all the original recipients to be failed,
27805 and a bounce message to be created. The &%freeze%& command suspends all
27806 delivery attempts for the original recipients. In all cases, any new deliveries
27807 that are specified by the filter are attempted as normal after the filter has
27810 The &%freeze%& command is ignored if the message has been manually unfrozen and
27811 not manually frozen since. This means that automatic freezing by a system
27812 filter can be used as a way of checking out suspicious messages. If a message
27813 is found to be all right, manually unfreezing it allows it to be delivered.
27815 .cindex "log" "&%fail%& command log line"
27816 .cindex "&%fail%&" "log line; reducing"
27817 The text given with a fail command is used as part of the bounce message as
27818 well as being written to the log. If the message is quite long, this can fill
27819 up a lot of log space when such failures are common. To reduce the size of the
27820 log message, Exim interprets the text in a special way if it starts with the
27821 two characters &`<<`& and contains &`>>`& later. The text between these two
27822 strings is written to the log, and the rest of the text is used in the bounce
27823 message. For example:
27825 fail "<<filter test 1>>Your message is rejected \
27826 because it contains attachments that we are \
27827 not prepared to receive."
27830 .cindex "loop" "caused by &%fail%&"
27831 Take great care with the &%fail%& command when basing the decision to fail on
27832 the contents of the message, because the bounce message will of course include
27833 the contents of the original message and will therefore trigger the &%fail%&
27834 command again (causing a mail loop) unless steps are taken to prevent this.
27835 Testing the &%error_message%& condition is one way to prevent this. You could
27838 if $message_body contains "this is spam" and not error_message
27839 then fail text "spam is not wanted here" endif
27841 though of course that might let through unwanted bounce messages. The
27842 alternative is clever checking of the body and/or headers to detect bounces
27843 generated by the filter.
27845 The interpretation of a system filter file ceases after a
27847 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
27848 set up earlier in the filter file are honoured, so you can use a sequence such
27854 to send a specified message when the system filter is freezing (or deferring or
27855 failing) a message. The normal deliveries for the message do not, of course,
27860 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
27861 .cindex "header lines" "adding; in system filter"
27862 .cindex "header lines" "removing; in system filter"
27863 .cindex "filter" "header lines; adding/removing"
27864 Two filter commands that are available only in system filters are:
27866 headers add <string>
27867 headers remove <string>
27869 The argument for the &%headers add%& is a string that is expanded and then
27870 added to the end of the message's headers. It is the responsibility of the
27871 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
27872 space is ignored, and if the string is otherwise empty, or if the expansion is
27873 forced to fail, the command has no effect.
27875 You can use &"\n"& within the string, followed by white space, to specify
27876 continued header lines. More than one header may be added in one command by
27877 including &"\n"& within the string without any following white space. For
27880 headers add "X-header-1: ....\n \
27881 continuation of X-header-1 ...\n\
27884 Note that the header line continuation white space after the first newline must
27885 be placed before the backslash that continues the input string, because white
27886 space after input continuations is ignored.
27888 The argument for &%headers remove%& is a colon-separated list of header names.
27889 This command applies only to those headers that are stored with the message;
27890 those that are added at delivery time (such as &'Envelope-To:'& and
27891 &'Return-Path:'&) cannot be removed by this means. If there is more than one
27892 header with the same name, they are all removed.
27894 The &%headers%& command in a system filter makes an immediate change to the set
27895 of header lines that was received with the message (with possible additions
27896 from ACL processing). Subsequent commands in the system filter operate on the
27897 modified set, which also forms the basis for subsequent message delivery.
27898 Unless further modified during routing or transporting, this set of headers is
27899 used for all recipients of the message.
27901 During routing and transporting, the variables that refer to the contents of
27902 header lines refer only to those lines that are in this set. Thus, header lines
27903 that are added by a system filter are visible to users' filter files and to all
27904 routers and transports. This contrasts with the manipulation of header lines by
27905 routers and transports, which is not immediate, but which instead is saved up
27906 until the message is actually being written (see section
27907 &<<SECTheadersaddrem>>&).
27909 If the message is not delivered at the first attempt, header lines that were
27910 added by the system filter are stored with the message, and so are still
27911 present at the next delivery attempt. Header lines that were removed are still
27912 present, but marked &"deleted"& so that they are not transported with the
27913 message. For this reason, it is usual to make the &%headers%& command
27914 conditional on &%first_delivery%& so that the set of header lines is not
27915 modified more than once.
27917 Because header modification in a system filter acts immediately, you have to
27918 use an indirect approach if you want to modify the contents of a header line.
27921 headers add "Old-Subject: $h_subject:"
27922 headers remove "Subject"
27923 headers add "Subject: new subject (was: $h_old-subject:)"
27924 headers remove "Old-Subject"
27929 .section "Setting an errors address in a system filter"
27930 .cindex "envelope sender"
27931 In a system filter, if a &%deliver%& command is followed by
27933 errors_to <some address>
27935 in order to change the envelope sender (and hence the error reporting) for that
27936 delivery, any address may be specified. (In a user filter, only the current
27937 user's address can be set.) For example, if some mail is being monitored, you
27940 unseen deliver monitor@spying.example errors_to root@local.example
27942 to take a copy which would not be sent back to the normal error reporting
27943 address if its delivery failed.
27947 .section "Per-address filtering" "SECTperaddfil"
27948 .cindex "&$domain$&"
27949 .cindex "&$local_part$&"
27950 In contrast to the system filter, which is run just once per message for each
27951 delivery attempt, it is also possible to set up a system-wide filtering
27952 operation that runs once for each recipient address. In this case, variables
27953 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
27954 filter file could be made dependent on them. This is an example of a router
27955 which implements such a filter:
27960 domains = +local_domains
27961 file = /central/filters/$local_part
27966 The filter is run in a separate process under its own uid. Therefore, either
27967 &%check_local_user%& must be set (as above), in which case the filter is run as
27968 the local user, or the &%user%& option must be used to specify which user to
27969 use. If both are set, &%user%& overrides.
27971 Care should be taken to ensure that none of the commands in the filter file
27972 specify a significant delivery if the message is to go on to be delivered to
27973 its intended recipient. The router will not then claim to have dealt with the
27974 address, so it will be passed on to subsequent routers to be delivered in the
27976 .ecindex IIDsysfil1
27977 .ecindex IIDsysfil2
27978 .ecindex IIDsysfil3
27985 . ////////////////////////////////////////////////////////////////////////////
27986 . ////////////////////////////////////////////////////////////////////////////
27988 .chapter "Message processing" "CHAPmsgproc"
27989 .scindex IIDmesproc "message" "general processing"
27990 Exim performs various transformations on the sender and recipient addresses of
27991 all messages that it handles, and also on the messages' header lines. Some of
27992 these are optional and configurable, while others always take place. All of
27993 this processing, except rewriting as a result of routing, and the addition or
27994 removal of header lines while delivering, happens when a message is received,
27995 before it is placed on Exim's queue.
27997 Some of the automatic processing takes place by default only for
27998 &"locally-originated"& messages. This adjective is used to describe messages
27999 that are not received over TCP/IP, but instead are passed to an Exim process on
28000 its standard input. This includes the interactive &"local SMTP"& case that is
28001 set up by the &%-bs%& command line option.
28003 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
28004 or ::1) are not considered to be locally-originated. Exim does not treat the
28005 loopback interface specially in any way.
28007 If you want the loopback interface to be treated specially, you must ensure
28008 that there are appropriate entries in your ACLs.
28013 .section "Submission mode for non-local messages" "SECTsubmodnon"
28014 .cindex "message" "submission"
28015 .cindex "submission mode"
28016 Processing that happens automatically for locally-originated messages (unless
28017 &%suppress_local_fixups%& is set) can also be requested for messages that are
28018 received over TCP/IP. The term &"submission mode"& is used to describe this
28019 state. Submisssion mode is set by the modifier
28021 control = submission
28023 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
28024 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
28025 a local submission, and is normally used when the source of the message is
28026 known to be an MUA running on a client host (as opposed to an MTA). For
28027 example, to set submission mode for messages originating on the IPv4 loopback
28028 interface, you could include the following in the MAIL ACL:
28030 warn hosts = 127.0.0.1
28031 control = submission
28033 .cindex "&%sender_retain%&"
28034 There are some options that can be used when setting submission mode. A slash
28035 is used to separate options. For example:
28037 control = submission/sender_retain
28039 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
28040 true and &%local_from_check%& false for the current incoming message. The first
28041 of these allows an existing &'Sender:'& header in the message to remain, and
28042 the second suppresses the check to ensure that &'From:'& matches the
28043 authenticated sender. With this setting, Exim still fixes up messages by adding
28044 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
28045 attempt to check sender authenticity in header lines.
28047 When &%sender_retain%& is not set, a submission mode setting may specify a
28048 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
28051 control = submission/domain=some.domain
28053 The domain may be empty. How this value is used is described in sections
28054 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
28055 that allows you to specify the user's full name for inclusion in a created
28056 &'Sender:'& or &'From:'& header line. For example:
28058 accept authenticated = *
28059 control = submission/domain=wonderland.example/\
28060 name=${lookup {$authenticated_id} \
28061 lsearch {/etc/exim/namelist}}
28063 Because the name may contain any characters, including slashes, the &%name%&
28064 option must be given last. The remainder of the string is used as the name. For
28065 the example above, if &_/etc/exim/namelist_& contains:
28067 bigegg: Humpty Dumpty
28069 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
28072 Sender: Humpty Dumpty <bigegg@wonderland.example>
28074 .cindex "return path" "in submission mode"
28075 By default, submission mode forces the return path to the same address as is
28076 used to create the &'Sender:'& header. However, if &%sender_retain%& is
28077 specified, the return path is also left unchanged.
28079 &*Note*&: The changes caused by submission mode take effect after the predata
28080 ACL. This means that any sender checks performed before the fix-ups use the
28081 untrusted sender address specified by the user, not the trusted sender address
28082 specified by submission mode. Although this might be slightly unexpected, it
28083 does mean that you can configure ACL checks to spot that a user is trying to
28084 spoof another's address.
28086 .section "Line endings" "SECTlineendings"
28087 .cindex "line endings"
28088 .cindex "carriage return"
28090 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
28091 linefeed) is the line ending for messages transmitted over the Internet using
28092 SMTP over TCP/IP. However, within individual operating systems, different
28093 conventions are used. For example, Unix-like systems use just LF, but others
28094 use CRLF or just CR.
28096 Exim was designed for Unix-like systems, and internally, it stores messages
28097 using the system's convention of a single LF as a line terminator. When
28098 receiving a message, all line endings are translated to this standard format.
28099 Originally, it was thought that programs that passed messages directly to an
28100 MTA within an operating system would use that system's convention. Experience
28101 has shown that this is not the case; for example, there are Unix applications
28102 that use CRLF in this circumstance. For this reason, and for compatibility with
28103 other MTAs, the way Exim handles line endings for all messages is now as
28107 LF not preceded by CR is treated as a line ending.
28109 CR is treated as a line ending; if it is immediately followed by LF, the LF
28112 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
28113 nor a local message in the state where a line containing only a dot is a
28116 If a bare CR is encountered within a header line, an extra space is added after
28117 the line terminator so as not to end the header line. The reasoning behind this
28118 is that bare CRs in header lines are most likely either to be mistakes, or
28119 people trying to play silly games.
28121 If the first header line received in a message ends with CRLF, a subsequent
28122 bare LF in a header line is treated in the same way as a bare CR in a header
28130 .section "Unqualified addresses"
28131 .cindex "unqualified addresses"
28132 .cindex "address" "qualification"
28133 By default, Exim expects every envelope address it receives from an external
28134 host to be fully qualified. Unqualified addresses cause negative responses to
28135 SMTP commands. However, because SMTP is used as a means of transporting
28136 messages from MUAs running on personal workstations, there is sometimes a
28137 requirement to accept unqualified addresses from specific hosts or IP networks.
28139 Exim has two options that separately control which hosts may send unqualified
28140 sender or receipient addresses in SMTP commands, namely
28141 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
28142 cases, if an unqualified address is accepted, it is qualified by adding the
28143 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
28145 .cindex "&%qualify_domain%&"
28146 .cindex "&%qualify_recipient%&"
28147 Unqualified addresses in header lines are automatically qualified for messages
28148 that are locally originated, unless the &%-bnq%& option is given on the command
28149 line. For messages received over SMTP, unqualified addresses in header lines
28150 are qualified only if unqualified addresses are permitted in SMTP commands. In
28151 other words, such qualification is also controlled by
28152 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
28157 .section "The UUCP From line"
28158 .cindex "&""From""& line"
28159 .cindex "UUCP" "&""From""& line"
28160 .cindex "sender" "address"
28161 .cindex "&%uucp_from_pattern%&"
28162 .cindex "&%uucp_from_sender%&"
28163 .cindex "envelope sender"
28164 .cindex "Sendmail compatibility" "&""From""& line"
28165 Messages that have come from UUCP (and some other applications) often begin
28166 with a line containing the envelope sender and a timestamp, following the word
28167 &"From"&. Examples of two common formats are:
28169 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
28170 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
28172 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
28173 Exim recognizes such lines at the start of messages that are submitted to it
28174 via the command line (that is, on the standard input). It does not recognize
28175 such lines in incoming SMTP messages, unless the sending host matches
28176 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
28177 and &%ignore_fromline_local%& is set. The recognition is controlled by a
28178 regular expression that is defined by the &%uucp_from_pattern%& option, whose
28179 default value matches the two common cases shown above and puts the address
28180 that follows &"From"& into &$1$&.
28182 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
28183 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
28184 a trusted user, the message's sender address is constructed by expanding the
28185 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
28186 then parsed as an RFC 2822 address. If there is no domain, the local part is
28187 qualified with &%qualify_domain%& unless it is the empty string. However, if
28188 the command line &%-f%& option is used, it overrides the &"From"& line.
28190 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
28191 sender address is not changed. This is also the case for incoming SMTP messages
28192 that are permitted to contain &"From"& lines.
28194 Only one &"From"& line is recognized. If there is more than one, the second is
28195 treated as a data line that starts the body of the message, as it is not valid
28196 as a header line. This also happens if a &"From"& line is present in an
28197 incoming SMTP message from a source that is not permitted to send them.
28201 .section "Resent- header lines"
28202 .cindex "&%Resent-%& header lines"
28203 RFC 2822 makes provision for sets of header lines starting with the string
28204 &`Resent-`& to be added to a message when it is resent by the original
28205 recipient to somebody else. These headers are &'Resent-Date:'&,
28206 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
28207 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
28210 &'Resent fields are strictly informational. They MUST NOT be used in the normal
28211 processing of replies or other such automatic actions on messages.'&
28214 This leaves things a bit vague as far as other processing actions such as
28215 address rewriting are concerned. Exim treats &%Resent-%& header lines as
28219 A &'Resent-From:'& line that just contains the login id of the submitting user
28220 is automatically rewritten in the same way as &'From:'& (see below).
28222 If there's a rewriting rule for a particular header line, it is also applied to
28223 &%Resent-%& header lines of the same type. For example, a rule that rewrites
28224 &'From:'& also rewrites &'Resent-From:'&.
28226 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
28229 For a locally-submitted message,
28230 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
28231 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
28232 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
28233 included in log lines in this case.
28235 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
28236 &%Resent-%& header lines are present.
28242 .section "The Auto-Submitted: header line"
28244 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
28245 includes the header line:
28248 Auto-Submitted: auto-replied
28251 .section "The Bcc: header line"
28252 .cindex "&'Bcc:'& header line"
28253 If Exim is called with the &%-t%& option, to take recipient addresses from a
28254 message's header, it removes any &'Bcc:'& header line that may exist (after
28255 extracting its addresses). If &%-t%& is not present on the command line, any
28256 existing &'Bcc:'& is not removed.
28259 .section "The Date: header line"
28260 .cindex "&'Date:'& header line"
28261 If a locally-generated or submission-mode message has no &'Date:'& header line,
28262 Exim adds one, using the current date and time, unless the
28263 &%suppress_local_fixups%& control has been specified.
28265 .section "The Delivery-date: header line"
28266 .cindex "&'Delivery-date:'& header line"
28267 .cindex "&%delivery_date_remove%&"
28268 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
28269 set. Exim can be configured to add them to the final delivery of messages. (See
28270 the generic &%delivery_date_add%& transport option.) They should not be present
28271 in messages in transit. If the &%delivery_date_remove%& configuration option is
28272 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
28276 .section "The Envelope-to: header line"
28277 .cindex "&'Envelope-to:'& header line"
28278 .cindex "&%envelope_to_remove%&"
28279 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
28280 Exim can be configured to add them to the final delivery of messages. (See the
28281 generic &%envelope_to_add%& transport option.) They should not be present in
28282 messages in transit. If the &%envelope_to_remove%& configuration option is set
28283 (the default), Exim removes &'Envelope-to:'& header lines from incoming
28287 .section "The From: header line" "SECTthefrohea"
28288 .cindex "&'From:'& header line"
28289 .cindex "Sendmail compatibility" "&""From""& line"
28290 .cindex "message" "submission"
28291 .cindex "submission mode"
28292 If a submission-mode message does not contain a &'From:'& header line, Exim
28293 adds one if either of the following conditions is true:
28296 The envelope sender address is not empty (that is, this is not a bounce
28297 message). The added header line copies the envelope sender address.
28299 .cindex "&$authenticated_id$&"
28300 The SMTP session is authenticated and &$authenticated_id$& is not empty.
28302 .cindex "&$qualify_domain$&"
28303 If no domain is specified by the submission control, the local part is
28304 &$authenticated_id$& and the domain is &$qualify_domain$&.
28306 If a non-empty domain is specified by the submission control, the local
28307 part is &$authenticated_id$&, and the the domain is the specified domain.
28309 If an empty domain is specified by the submission control,
28310 &$authenticated_id$& is assumed to be the complete address.
28314 A non-empty envelope sender takes precedence.
28316 If a locally-generated incoming message does not contain a &'From:'& header
28317 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
28318 containing the sender's address. The calling user's login name and full name
28319 are used to construct the address, as described in section &<<SECTconstr>>&.
28320 They are obtained from the password data by calling &[getpwuid()]& (but see the
28321 &%unknown_login%& configuration option). The address is qualified with
28322 &%qualify_domain%&.
28324 For compatibility with Sendmail, if an incoming, non-SMTP message has a
28325 &'From:'& header line containing just the unqualified login name of the calling
28326 user, this is replaced by an address containing the user's login name and full
28327 name as described in section &<<SECTconstr>>&.
28330 .section "The Message-ID: header line"
28331 .cindex "&'Message-ID:'& header line"
28332 .cindex "message" "submission"
28333 .cindex "&%message_id_header_text%&"
28334 If a locally-generated or submission-mode incoming message does not contain a
28335 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
28336 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
28337 to the message. If there are any &'Resent-:'& headers in the message, it
28338 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
28339 message id, preceded by the letter E to ensure it starts with a letter, and
28340 followed by @ and the primary host name. Additional information can be included
28341 in this header line by setting the &%message_id_header_text%& and/or
28342 &%message_id_header_domain%& options.
28345 .section "The Received: header line"
28346 .cindex "&'Received:'& header line"
28347 A &'Received:'& header line is added at the start of every message. The
28348 contents are defined by the &%received_header_text%& configuration option, and
28349 Exim automatically adds a semicolon and a timestamp to the configured string.
28351 The &'Received:'& header is generated as soon as the message's header lines
28352 have been received. At this stage, the timestamp in the &'Received:'& header
28353 line is the time that the message started to be received. This is the value
28354 that is seen by the DATA ACL and by the &[local_scan()]& function.
28356 Once a message is accepted, the timestamp in the &'Received:'& header line is
28357 changed to the time of acceptance, which is (apart from a small delay while the
28358 -H spool file is written) the earliest time at which delivery could start.
28362 .section "The References: header line"
28363 .cindex "&'References:'& header line"
28364 Messages created by the &(autoreply)& transport include a &'References:'&
28365 header line. This is constructed according to the rules that are described in
28366 section 3.64 of RFC 2822 (which states that replies should contain such a
28367 header line), and section 3.14 of RFC 3834 (which states that automatic
28368 responses are not different in this respect). However, because some mail
28369 processing software does not cope well with very long header lines, no more
28370 than 12 message IDs are copied from the &'References:'& header line in the
28371 incoming message. If there are more than 12, the first one and then the final
28372 11 are copied, before adding the message ID of the incoming message.
28377 .section "The Return-path: header line"
28378 .cindex "&'Return-path:'& header line"
28379 .cindex "&%return_path_remove%&"
28380 &'Return-path:'& header lines are defined as something an MTA may insert when
28381 it does the final delivery of messages. (See the generic &%return_path_add%&
28382 transport option.) Therefore, they should not be present in messages in
28383 transit. If the &%return_path_remove%& configuration option is set (the
28384 default), Exim removes &'Return-path:'& header lines from incoming messages.
28388 .section "The Sender: header line" "SECTthesenhea"
28389 .cindex "&'Sender:'& header line"
28390 .cindex "message" "submission"
28391 For a locally-originated message from an untrusted user, Exim may remove an
28392 existing &'Sender:'& header line, and it may add a new one. You can modify
28393 these actions by setting the &%local_sender_retain%& option true, the
28394 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
28397 When a local message is received from an untrusted user and
28398 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
28399 control has not been set, a check is made to see if the address given in the
28400 &'From:'& header line is the correct (local) sender of the message. The address
28401 that is expected has the login name as the local part and the value of
28402 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
28403 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
28404 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
28405 line is added to the message.
28407 If you set &%local_from_check%& false, this checking does not occur. However,
28408 the removal of an existing &'Sender:'& line still happens, unless you also set
28409 &%local_sender_retain%& to be true. It is not possible to set both of these
28410 options true at the same time.
28412 .cindex "submission mode"
28413 By default, no processing of &'Sender:'& header lines is done for messages
28414 received over TCP/IP or for messages submitted by trusted users. However, when
28415 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
28416 not specified on the submission control, the following processing takes place:
28418 .cindex "&$authenticated_id$&"
28419 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
28420 authenticated, and &$authenticated_id$& is not empty, a sender address is
28421 created as follows:
28424 .cindex "&$qualify_domain$&"
28425 If no domain is specified by the submission control, the local part is
28426 &$authenticated_id$& and the domain is &$qualify_domain$&.
28428 If a non-empty domain is specified by the submission control, the local part
28429 is &$authenticated_id$&, and the the domain is the specified domain.
28431 If an empty domain is specified by the submission control,
28432 &$authenticated_id$& is assumed to be the complete address.
28435 This address is compared with the address in the &'From:'& header line. If they
28436 are different, a &'Sender:'& header line containing the created address is
28437 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
28438 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
28440 .cindex "return path" "created from &'Sender:'&"
28441 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
28442 the message (the envelope sender address) is changed to be the same address,
28443 except in the case of submission mode when &%sender_retain%& is specified.
28447 .section "Adding and removing header lines in routers and transports" &&&
28448 "SECTheadersaddrem"
28449 .cindex "header lines" "adding; in router or transport"
28450 .cindex "header lines" "removing; in router or transport"
28451 When a message is delivered, the addition and removal of header lines can be
28452 specified in a system filter, or on any of the routers and transports that
28453 process the message. Section &<<SECTaddremheasys>>& contains details about
28454 modifying headers in a system filter. Header lines can also be added in an ACL
28455 as a message is received (see section &<<SECTaddheadacl>>&).
28457 In contrast to what happens in a system filter, header modifications that are
28458 specified on routers and transports apply only to the particular recipient
28459 addresses that are being processed by those routers and transports. These
28460 changes do not actually take place until a copy of the message is being
28461 transported. Therefore, they do not affect the basic set of header lines, and
28462 they do not affect the values of the variables that refer to header lines.
28464 &*Note*&: In particular, this means that any expansions in the configuration of
28465 the transport cannot refer to the modified header lines, because such
28466 expansions all occur before the message is actually transported.
28468 For both routers and transports, the result of expanding a &%headers_add%&
28469 option must be in the form of one or more RFC 2822 header lines, separated by
28470 newlines (coded as &"\n"&). For example:
28472 headers_add = X-added-header: added by $primary_hostname\n\
28473 X-added-second: another added header line
28475 Exim does not check the syntax of these added header lines.
28477 The result of expanding &%headers_remove%& must consist of a colon-separated
28478 list of header names. This is confusing, because header names themselves are
28479 often terminated by colons. In this case, the colons are the list separators,
28480 not part of the names. For example:
28482 headers_remove = return-receipt-to:acknowledge-to
28484 When &%headers_add%& or &%headers_remove%& is specified on a router, its value
28485 is expanded at routing time, and then associated with all addresses that are
28486 accepted by that router, and also with any new addresses that it generates. If
28487 an address passes through several routers as a result of aliasing or
28488 forwarding, the changes are cumulative.
28490 .cindex "&%unseen%& option"
28491 However, this does not apply to multiple routers that result from the use of
28492 the &%unseen%& option. Any header modifications that were specified by the
28493 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
28495 Addresses that end up with different &%headers_add%& or &%headers_remove%&
28496 settings cannot be delivered together in a batch, so a transport is always
28497 dealing with a set of addresses that have the same header-processing
28500 The transport starts by writing the original set of header lines that arrived
28501 with the message, possibly modified by the system filter. As it writes out
28502 these lines, it consults the list of header names that were attached to the
28503 recipient address(es) by &%headers_remove%& options in routers, and it also
28504 consults the transport's own &%headers_remove%& option. Header lines whose
28505 names are on either of these lists are not written out. If there are multiple
28506 instances of any listed header, they are all skipped.
28508 After the remaining original header lines have been written, new header
28509 lines that were specified by routers' &%headers_add%& options are written, in
28510 the order in which they were attached to the address. These are followed by any
28511 header lines specified by the transport's &%headers_add%& option.
28513 This way of handling header line modifications in routers and transports has
28514 the following consequences:
28517 The original set of header lines, possibly modified by the system filter,
28518 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
28519 to it, at all times.
28521 Header lines that are added by a router's
28522 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
28523 expansion syntax in subsequent routers or the transport.
28525 Conversely, header lines that are specified for removal by &%headers_remove%&
28526 in a router remain visible to subsequent routers and the transport.
28528 Headers added to an address by &%headers_add%& in a router cannot be removed by
28529 a later router or by a transport.
28531 An added header can refer to the contents of an original header that is to be
28532 removed, even it has the same name as the added header. For example:
28534 headers_remove = subject
28535 headers_add = Subject: new subject (was: $h_subject:)
28539 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
28540 for a &(redirect)& router that has the &%one_time%& option set.
28546 .section "Constructed addresses" "SECTconstr"
28547 .cindex "address" "constructed"
28548 .cindex "constructed address"
28549 When Exim constructs a sender address for a locally-generated message, it uses
28552 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
28556 Zaphod Beeblebrox <zaphod@end.univ.example>
28558 The user name is obtained from the &%-F%& command line option if set, or
28559 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
28560 &"gecos"& field from the password entry. If the &"gecos"& field contains an
28561 ampersand character, this is replaced by the login name with the first letter
28562 upper cased, as is conventional in a number of operating systems. See the
28563 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
28564 The &%unknown_username%& option can be used to specify user names in cases when
28565 there is no password file entry.
28568 In all cases, the user name is made to conform to RFC 2822 by quoting all or
28569 parts of it if necessary. In addition, if it contains any non-printing
28570 characters, it is encoded as described in RFC 2047, which defines a way of
28571 including non-ASCII characters in header lines. The value of the
28572 &%headers_charset%& option specifies the name of the encoding that is used (the
28573 characters are assumed to be in this encoding). The setting of
28574 &%print_topbitchars%& controls whether characters with the top bit set (that
28575 is, with codes greater than 127) count as printing characters or not.
28579 .section "Case of local parts"
28580 .cindex "case of local parts"
28581 .cindex "local part" "case of"
28582 RFC 2822 states that the case of letters in the local parts of addresses cannot
28583 be assumed to be non-significant. Exim preserves the case of local parts of
28584 addresses, but by default it uses a lower-cased form when it is routing,
28585 because on most Unix systems, usernames are in lower case and case-insensitive
28586 routing is required. However, any particular router can be made to use the
28587 original case for local parts by setting the &%caseful_local_part%& generic
28590 .cindex "mixed-case login names"
28591 If you must have mixed-case user names on your system, the best way to proceed,
28592 assuming you want case-independent handling of incoming email, is to set up
28593 your first router to convert incoming local parts in your domains to the
28594 correct case by means of a file lookup. For example:
28598 domains = +local_domains
28599 data = ${lookup{$local_part}cdb\
28600 {/etc/usercased.cdb}{$value}fail}\
28603 For this router, the local part is forced to lower case by the default action
28604 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
28605 up a new local part in the correct case. If you then set &%caseful_local_part%&
28606 on any subsequent routers which process your domains, they will operate on
28607 local parts with the correct case in a case-sensitive manner.
28611 .section "Dots in local parts"
28612 .cindex "dot" "in local part"
28613 .cindex "local part" "dots in"
28614 RFC 2822 forbids empty components in local parts. That is, an unquoted local
28615 part may not begin or end with a dot, nor have two consecutive dots in the
28616 middle. However, it seems that many MTAs do not enforce this, so Exim permits
28617 empty components for compatibility.
28621 .section "Rewriting addresses"
28622 .cindex "rewriting" "addresses"
28623 Rewriting of sender and recipient addresses, and addresses in headers, can
28624 happen automatically, or as the result of configuration options, as described
28625 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
28626 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
28628 Automatic rewriting includes qualification, as mentioned above. The other case
28629 in which it can happen is when an incomplete non-local domain is given. The
28630 routing process may cause this to be expanded into the full domain name. For
28631 example, a header such as
28635 might get rewritten as
28637 To: hare@teaparty.wonderland.fict.example
28639 Rewriting as a result of routing is the one kind of message processing that
28640 does not happen at input time, as it cannot be done until the address has
28643 Strictly, one should not do &'any'& deliveries of a message until all its
28644 addresses have been routed, in case any of the headers get changed as a
28645 result of routing. However, doing this in practice would hold up many
28646 deliveries for unreasonable amounts of time, just because one address could not
28647 immediately be routed. Exim therefore does not delay other deliveries when
28648 routing of one or more addresses is deferred.
28649 .ecindex IIDmesproc
28653 . ////////////////////////////////////////////////////////////////////////////
28654 . ////////////////////////////////////////////////////////////////////////////
28656 .chapter "SMTP processing" "CHAPSMTP"
28657 .scindex IIDsmtpproc1 "SMTP" "processing details"
28658 .scindex IIDsmtpproc2 "LMTP" "processing details"
28659 Exim supports a number of different ways of using the SMTP protocol, and its
28660 LMTP variant, which is an interactive protocol for transferring messages into a
28661 closed mail store application. This chapter contains details of how SMTP is
28662 processed. For incoming mail, the following are available:
28665 SMTP over TCP/IP (Exim daemon or &'inetd'&);
28667 SMTP over the standard input and output (the &%-bs%& option);
28669 Batched SMTP on the standard input (the &%-bS%& option).
28672 For mail delivery, the following are available:
28675 SMTP over TCP/IP (the &(smtp)& transport);
28677 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
28680 LMTP over a pipe to a process running in the local host (the &(lmtp)&
28683 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
28684 the &%use_bsmtp%& option set).
28687 &'Batched SMTP'& is the name for a process in which batches of messages are
28688 stored in or read from files (or pipes), in a format in which SMTP commands are
28689 used to contain the envelope information.
28693 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
28694 .cindex "SMTP" "outgoing over TCP/IP"
28695 .cindex "outgoing SMTP over TCP/IP"
28696 .cindex "LMTP" "over TCP/IP"
28697 .cindex "outgoing LMTP over TCP/IP"
28700 .cindex "SIZE option on MAIL command"
28701 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
28702 The &%protocol%& option selects which protocol is to be used, but the actual
28703 processing is the same in both cases.
28705 If, in response to its EHLO command, Exim is told that the SIZE
28706 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
28707 command. The value of <&'n'&> is the message size plus the value of the
28708 &%size_addition%& option (default 1024) to allow for additions to the message
28709 such as per-transport header lines, or changes made in a
28710 .cindex "transport" "filter"
28711 .cindex "filter" "transport filter"
28712 transport filter. If &%size_addition%& is set negative, the use of SIZE is
28715 If the remote server advertises support for PIPELINING, Exim uses the
28716 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
28717 required for the transaction.
28719 If the remote server advertises support for the STARTTLS command, and Exim
28720 was built to support TLS encryption, it tries to start a TLS session unless the
28721 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
28723 If the remote server advertises support for the AUTH command, Exim scans
28724 the authenticators configuration for any suitable client settings, as described
28725 in chapter &<<CHAPSMTPAUTH>>&.
28727 .cindex "carriage return"
28729 Responses from the remote host are supposed to be terminated by CR followed by
28730 LF. However, there are known to be hosts that do not send CR characters, so in
28731 order to be able to interwork with such hosts, Exim treats LF on its own as a
28734 If a message contains a number of different addresses, all those with the same
28735 characteristics (for example, the same envelope sender) that resolve to the
28736 same set of hosts, in the same order, are sent in a single SMTP transaction,
28737 even if they are for different domains, unless there are more than the setting
28738 of the &%max_rcpts%& option in the &(smtp)& transport allows, in which case
28739 they are split into groups containing no more than &%max_rcpts%& addresses
28740 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
28741 in parallel sessions. The order of hosts with identical MX values is not
28742 significant when checking whether addresses can be batched in this way.
28744 When the &(smtp)& transport suffers a temporary failure that is not
28745 message-related, Exim updates its transport-specific database, which contains
28746 records indexed by host name that remember which messages are waiting for each
28747 particular host. It also updates the retry database with new retry times.
28749 .cindex "hints database" "retry keys"
28750 Exim's retry hints are based on host name plus IP address, so if one address of
28751 a multi-homed host is broken, it will soon be skipped most of the time.
28752 See the next section for more detail about error handling.
28754 .cindex "SMTP" "passed connection"
28755 .cindex "SMTP" "batching over TCP/IP"
28756 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
28757 looks in the hints database for the transport to see if there are any queued
28758 messages waiting for the host to which it is connected. If it finds one, it
28759 creates a new Exim process using the &%-MC%& option (which can only be used by
28760 a process running as root or the Exim user) and passes the TCP/IP socket to it
28761 so that it can deliver another message using the same socket. The new process
28762 does only those deliveries that are routed to the connected host, and may in
28763 turn pass the socket on to a third process, and so on.
28765 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
28766 limit the number of messages sent down a single TCP/IP connection.
28768 .cindex "asterisk" "after IP address"
28769 The second and subsequent messages delivered down an existing connection are
28770 identified in the main log by the addition of an asterisk after the closing
28771 square bracket of the IP address.
28776 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
28777 .cindex "error" "in outgoing SMTP"
28778 .cindex "SMTP" "errors in outgoing"
28779 .cindex "host" "error"
28780 Three different kinds of error are recognized for outgoing SMTP: host errors,
28781 message errors, and recipient errors.
28784 .vitem "&*Host errors*&"
28785 A host error is not associated with a particular message or with a
28786 particular recipient of a message. The host errors are:
28789 Connection refused or timed out,
28791 Any error response code on connection,
28793 Any error response code to EHLO or HELO,
28795 Loss of connection at any time, except after &"."&,
28797 I/O errors at any time,
28799 Timeouts during the session, other than in response to MAIL, RCPT or
28800 the &"."& at the end of the data.
28803 For a host error, a permanent error response on connection, or in response to
28804 EHLO, causes all addresses routed to the host to be failed. Any other host
28805 error causes all addresses to be deferred, and retry data to be created for the
28806 host. It is not tried again, for any message, until its retry time arrives. If
28807 the current set of addresses are not all delivered in this run (to some
28808 alternative host), the message is added to the list of those waiting for this
28809 host, so if it is still undelivered when a subsequent successful delivery is
28810 made to the host, it will be sent down the same SMTP connection.
28812 .vitem "&*Message errors*&"
28813 .cindex "message" "error"
28814 A message error is associated with a particular message when sent to a
28815 particular host, but not with a particular recipient of the message. The
28816 message errors are:
28819 Any error response code to MAIL, DATA, or the &"."& that terminates
28822 Timeout after MAIL,
28824 Timeout or loss of connection after the &"."& that terminates the data. A
28825 timeout after the DATA command itself is treated as a host error, as is loss of
28826 connection at any other time.
28829 For a message error, a permanent error response (5&'xx'&) causes all addresses
28830 to be failed, and a delivery error report to be returned to the sender. A
28831 temporary error response (4&'xx'&), or one of the timeouts, causes all
28832 addresses to be deferred. Retry data is not created for the host, but instead,
28833 a retry record for the combination of host plus message id is created. The
28834 message is not added to the list of those waiting for this host. This ensures
28835 that the failing message will not be sent to this host again until the retry
28836 time arrives. However, other messages that are routed to the host are not
28837 affected, so if it is some property of the message that is causing the error,
28838 it will not stop the delivery of other mail.
28840 If the remote host specified support for the SIZE parameter in its response
28841 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
28842 over-large message will cause a message error because the error arrives as a
28845 .vitem "&*Recipient errors*&"
28846 .cindex "recipient" "error"
28847 A recipient error is associated with a particular recipient of a message. The
28848 recipient errors are:
28851 Any error response to RCPT,
28853 Timeout after RCPT.
28856 For a recipient error, a permanent error response (5&'xx'&) causes the
28857 recipient address to be failed, and a bounce message to be returned to the
28858 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
28859 address to be deferred, and routing retry data to be created for it. This is
28860 used to delay processing of the address in subsequent queue runs, until its
28861 routing retry time arrives. This applies to all messages, but because it
28862 operates only in queue runs, one attempt will be made to deliver a new message
28863 to the failing address before the delay starts to operate. This ensures that,
28864 if the failure is really related to the message rather than the recipient
28865 (&"message too big for this recipient"& is a possible example), other messages
28866 have a chance of getting delivered. If a delivery to the address does succeed,
28867 the retry information gets cleared, so all stuck messages get tried again, and
28868 the retry clock is reset.
28870 The message is not added to the list of those waiting for this host. Use of the
28871 host for other messages is unaffected, and except in the case of a timeout,
28872 other recipients are processed independently, and may be successfully delivered
28873 in the current SMTP session. After a timeout it is of course impossible to
28874 proceed with the session, so all addresses get deferred. However, those other
28875 than the one that failed do not suffer any subsequent retry delays. Therefore,
28876 if one recipient is causing trouble, the others have a chance of getting
28877 through when a subsequent delivery attempt occurs before the failing
28878 recipient's retry time.
28881 In all cases, if there are other hosts (or IP addresses) available for the
28882 current set of addresses (for example, from multiple MX records), they are
28883 tried in this run for any undelivered addresses, subject of course to their
28884 own retry data. In other words, recipient error retry data does not take effect
28885 until the next delivery attempt.
28887 Some hosts have been observed to give temporary error responses to every
28888 MAIL command at certain times (&"insufficient space"& has been seen). It
28889 would be nice if such circumstances could be recognized, and defer data for the
28890 host itself created, but this is not possible within the current Exim design.
28891 What actually happens is that retry data for every (host, message) combination
28894 The reason that timeouts after MAIL and RCPT are treated specially is that
28895 these can sometimes arise as a result of the remote host's verification
28896 procedures. Exim makes this assumption, and treats them as if a temporary error
28897 response had been received. A timeout after &"."& is treated specially because
28898 it is known that some broken implementations fail to recognize the end of the
28899 message if the last character of the last line is a binary zero. Thus, it is
28900 helpful to treat this case as a message error.
28902 Timeouts at other times are treated as host errors, assuming a problem with the
28903 host, or the connection to it. If a timeout after MAIL, RCPT,
28904 or &"."& is really a connection problem, the assumption is that at the next try
28905 the timeout is likely to occur at some other point in the dialogue, causing it
28906 then to be treated as a host error.
28908 There is experimental evidence that some MTAs drop the connection after the
28909 terminating &"."& if they do not like the contents of the message for some
28910 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
28911 should be given. That is why Exim treats this case as a message rather than a
28912 host error, in order not to delay other messages to the same host.
28917 .section "Incoming SMTP messages over TCP/IP"
28918 .cindex "SMTP" "incoming over TCP/IP"
28919 .cindex "incoming SMTP over TCP/IP"
28922 Incoming SMTP messages can be accepted in one of two ways: by running a
28923 listening daemon, or by using &'inetd'&. In the latter case, the entry in
28924 &_/etc/inetd.conf_& should be like this:
28926 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
28928 Exim distinguishes between this case and the case of a locally running user
28929 agent using the &%-bs%& option by checking whether or not the standard input is
28930 a socket. When it is, either the port must be privileged (less than 1024), or
28931 the caller must be root or the Exim user. If any other user passes a socket
28932 with an unprivileged port number, Exim prints a message on the standard error
28933 stream and exits with an error code.
28935 By default, Exim does not make a log entry when a remote host connects or
28936 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
28937 unexpected. It can be made to write such log entries by setting the
28938 &%smtp_connection%& log selector.
28940 .cindex "carriage return"
28942 Commands from the remote host are supposed to be terminated by CR followed by
28943 LF. However, there are known to be hosts that do not send CR characters. In
28944 order to be able to interwork with such hosts, Exim treats LF on its own as a
28946 Furthermore, because common code is used for receiving messages from all
28947 sources, a CR on its own is also interpreted as a line terminator. However, the
28948 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
28950 .cindex "EHLO" "invalid data"
28951 .cindex "HELO" "invalid data"
28952 One area that sometimes gives rise to problems concerns the EHLO or
28953 HELO commands. Some clients send syntactically invalid versions of these
28954 commands, which Exim rejects by default. (This is nothing to do with verifying
28955 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
28956 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
28957 match the broken hosts that send invalid commands.
28959 .cindex "SIZE option on MAIL command"
28960 .cindex "MAIL" "SIZE option"
28961 The amount of disk space available is checked whenever SIZE is received on
28962 a MAIL command, independently of whether &%message_size_limit%& or
28963 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
28964 false. A temporary error is given if there is not enough space. If
28965 &%check_spool_space%& is set, the check is for that amount of space plus the
28966 value given with SIZE, that is, it checks that the addition of the incoming
28967 message will not reduce the space below the threshold.
28969 When a message is successfully received, Exim includes the local message id in
28970 its response to the final &"."& that terminates the data. If the remote host
28971 logs this text it can help with tracing what has happened to a message.
28973 The Exim daemon can limit the number of simultaneous incoming connections it is
28974 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
28975 number of simultaneous incoming connections from a single remote host (see the
28976 &%smtp_accept_max_per_host%& option). Additional connection attempts are
28977 rejected using the SMTP temporary error code 421.
28979 The Exim daemon does not rely on the SIGCHLD signal to detect when a
28980 subprocess has finished, as this can get lost at busy times. Instead, it looks
28981 for completed subprocesses every time it wakes up. Provided there are other
28982 things happening (new incoming calls, starts of queue runs), completed
28983 processes will be noticed and tidied away. On very quiet systems you may
28984 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
28985 it will be noticed when the daemon next wakes up.
28987 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
28988 and can also be set up to reject SMTP calls from non-reserved hosts at times of
28989 high system load &-- for details see the &%smtp_accept_reserve%&,
28990 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
28991 applies in both the daemon and &'inetd'& cases.
28993 Exim normally starts a delivery process for each message received, though this
28994 can be varied by means of the &%-odq%& command line option and the
28995 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
28996 number of simultaneously running delivery processes started in this way from
28997 SMTP input can be limited by the &%smtp_accept_queue%& and
28998 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
28999 subsequently received messages are just put on the input queue without starting
29000 a delivery process.
29002 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
29003 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
29004 started up from the &'inetd'& daemon, because in that case each connection is
29005 handled by an entirely independent Exim process. Control by load average is,
29006 however, available with &'inetd'&.
29008 Exim can be configured to verify addresses in incoming SMTP commands as they
29009 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
29010 to rewrite addresses at this time &-- before any syntax checking is done. See
29011 section &<<SECTrewriteS>>&.
29013 Exim can also be configured to limit the rate at which a client host submits
29014 MAIL and RCPT commands in a single SMTP session. See the
29015 &%smtp_ratelimit_hosts%& option.
29019 .section "Unrecognized SMTP commands"
29020 .cindex "SMTP" "unrecognized commands"
29021 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
29022 commands during a single SMTP connection, it drops the connection after sending
29023 the error response to the last command. The default value for
29024 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
29025 abuse that subvert web servers into making connections to SMTP ports; in these
29026 circumstances, a number of non-SMTP lines are sent first.
29029 .section "Syntax and protocol errors in SMTP commands"
29030 .cindex "SMTP" "syntax errors"
29031 .cindex "SMTP" "protocol errors"
29032 A syntax error is detected if an SMTP command is recognized, but there is
29033 something syntactically wrong with its data, for example, a malformed email
29034 address in a RCPT command. Protocol errors include invalid command
29035 sequencing such as RCPT before MAIL. If Exim receives more than
29036 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
29037 drops the connection after sending the error response to the last command. The
29038 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
29039 broken clients that loop sending bad commands (yes, it has been seen).
29043 .section "Use of non-mail SMTP commands"
29044 .cindex "SMTP" "non-mail commands"
29045 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
29046 DATA. Exim counts such commands, and drops the connection if there are too
29047 many of them in a single SMTP session. This action catches some
29048 denial-of-service attempts and things like repeated failing AUTHs, or a mad
29049 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
29050 defines what &"too many"& means. Its default value is 10.
29052 When a new message is expected, one occurrence of RSET is not counted. This
29053 allows a client to send one RSET between messages (this is not necessary,
29054 but some clients do it). Exim also allows one uncounted occurence of HELO
29055 or EHLO, and one occurrence of STARTTLS between messages. After
29056 starting up a TLS session, another EHLO is expected, and so it too is not
29059 The first occurrence of AUTH in a connection, or immediately following
29060 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
29061 RCPT, DATA, and QUIT are counted.
29063 You can control which hosts are subject to the limit set by
29064 &%smtp_accept_max_nonmail%& by setting
29065 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
29066 the limit apply to all hosts. This option means that you can exclude any
29067 specific badly-behaved hosts that you have to live with.
29072 .section "The VRFY and EXPN commands"
29073 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
29074 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
29075 appropriate) in order to decide whether the command should be accepted or not.
29076 If no ACL is defined, the command is rejected.
29078 .cindex "VRFY" "processing"
29079 When VRFY is accepted, it runs exactly the same code as when Exim is
29080 called with the &%-bv%& option.
29082 .cindex "EXPN" "processing"
29083 When EXPN is accepted, a single-level expansion of the address is done.
29084 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
29085 than a verification (the &%-bv%& option). If an unqualified local part is given
29086 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
29087 of VRFY and EXPN commands are logged on the main and reject logs, and
29088 VRFY verification failures are logged on the main log for consistency with
29093 .section "The ETRN command" "SECTETRN"
29094 .cindex "ETRN" "processing"
29095 RFC 1985 describes an SMTP command called ETRN that is designed to
29096 overcome the security problems of the TURN command (which has fallen into
29097 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
29098 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
29099 should be accepted or not. If no ACL is defined, the command is rejected.
29101 The ETRN command is concerned with &"releasing"& messages that are awaiting
29102 delivery to certain hosts. As Exim does not organize its message queue by host,
29103 the only form of ETRN that is supported by default is the one where the
29104 text starts with the &"#"& prefix, in which case the remainder of the text is
29105 specific to the SMTP server. A valid ETRN command causes a run of Exim with
29106 the &%-R%& option to happen, with the remainder of the ETRN text as its
29107 argument. For example,
29115 which causes a delivery attempt on all messages with undelivered addresses
29116 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
29117 default), Exim prevents the simultaneous execution of more than one queue run
29118 for the same argument string as a result of an ETRN command. This stops
29119 a misbehaving client from starting more than one queue runner at once.
29121 .cindex "hints database" "ETRN serialization"
29122 Exim implements the serialization by means of a hints database in which a
29123 record is written whenever a process is started by ETRN, and deleted when
29124 the process completes. However, Exim does not keep the SMTP session waiting for
29125 the ETRN process to complete. Once ETRN is accepted, the client is sent
29126 a &"success"& return code. Obviously there is scope for hints records to get
29127 left lying around if there is a system or program crash. To guard against this,
29128 Exim ignores any records that are more than six hours old.
29130 .cindex "&%smtp_etrn_command%&"
29131 For more control over what ETRN does, the &%smtp_etrn_command%& option can
29132 used. This specifies a command that is run whenever ETRN is received,
29133 whatever the form of its argument. For
29136 smtp_etrn_command = /etc/etrn_command $domain \
29137 $sender_host_address
29139 .cindex "&$domain$&"
29140 The string is split up into arguments which are independently expanded. The
29141 expansion variable &$domain$& is set to the argument of the ETRN command,
29142 and no syntax checking is done on the contents of this argument. Exim does not
29143 wait for the command to complete, so its status code is not checked. Exim runs
29144 under its own uid and gid when receiving incoming SMTP, so it is not possible
29145 for it to change them before running the command.
29149 .section "Incoming local SMTP"
29150 .cindex "SMTP" "local incoming"
29151 Some user agents use SMTP to pass messages to their local MTA using the
29152 standard input and output, as opposed to passing the envelope on the command
29153 line and writing the message to the standard input. This is supported by the
29154 &%-bs%& option. This form of SMTP is handled in the same way as incoming
29155 messages over TCP/IP (including the use of ACLs), except that the envelope
29156 sender given in a MAIL command is ignored unless the caller is trusted. In
29157 an ACL you can detect this form of SMTP input by testing for an empty host
29158 identification. It is common to have this as the first line in the ACL that
29159 runs for RCPT commands:
29163 This accepts SMTP messages from local processes without doing any other tests.
29167 .section "Outgoing batched SMTP" "SECTbatchSMTP"
29168 .cindex "SMTP" "batched outgoing"
29169 .cindex "batched SMTP output"
29170 Both the &(appendfile)& and &(pipe)& transports can be used for handling
29171 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
29172 be output in BSMTP format. No SMTP responses are possible for this form of
29173 delivery. All it is doing is using SMTP commands as a way of transmitting the
29174 envelope along with the message.
29176 The message is written to the file or pipe preceded by the SMTP commands
29177 MAIL and RCPT, and followed by a line containing a single dot. Lines in
29178 the message that start with a dot have an extra dot added. The SMTP command
29179 HELO is not normally used. If it is required, the &%message_prefix%& option
29180 can be used to specify it.
29182 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
29183 one recipient address at a time by default. However, you can arrange for them
29184 to handle several addresses at once by setting the &%batch_max%& option. When
29185 this is done for BSMTP, messages may contain multiple RCPT commands. See
29186 chapter &<<CHAPbatching>>& for more details.
29189 When one or more addresses are routed to a BSMTP transport by a router that
29190 sets up a host list, the name of the first host on the list is available to the
29191 transport in the variable &$host$&. Here is an example of such a transport and
29196 driver = manualroute
29197 transport = smtp_appendfile
29198 route_list = domain.example batch.host.example
29202 driver = appendfile
29203 directory = /var/bsmtp/$host
29208 This causes messages addressed to &'domain.example'& to be written in BSMTP
29209 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
29210 message (unless there are more than 1000 recipients).
29214 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
29215 .cindex "SMTP" "batched incoming"
29216 .cindex "batched SMTP input"
29217 The &%-bS%& command line option causes Exim to accept one or more messages by
29218 reading SMTP on the standard input, but to generate no responses. If the caller
29219 is trusted, the senders in the MAIL commands are believed; otherwise the
29220 sender is always the caller of Exim. Unqualified senders and receivers are not
29221 rejected (there seems little point) but instead just get qualified. HELO
29222 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
29223 as NOOP; QUIT quits.
29225 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
29226 In this respect it is like non-SMTP local input.
29228 If an error is detected while reading a message, including a missing &"."& at
29229 the end, Exim gives up immediately. It writes details of the error to the
29230 standard output in a stylized way that the calling program should be able to
29231 make some use of automatically, for example:
29233 554 Unexpected end of file
29234 Transaction started in line 10
29235 Error detected in line 14
29237 It writes a more verbose version, for human consumption, to the standard error
29240 An error was detected while processing a file of BSMTP input.
29241 The error message was:
29243 501 '>' missing at end of address
29245 The SMTP transaction started in line 10.
29246 The error was detected in line 12.
29247 The SMTP command at fault was:
29249 rcpt to:<malformed@in.com.plete
29251 1 previous message was successfully processed.
29252 The rest of the batch was abandoned.
29254 The return code from Exim is zero only if there were no errors. It is 1 if some
29255 messages were accepted before an error was detected, and 2 if no messages were
29257 .ecindex IIDsmtpproc1
29258 .ecindex IIDsmtpproc2
29262 . ////////////////////////////////////////////////////////////////////////////
29263 . ////////////////////////////////////////////////////////////////////////////
29265 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
29266 "Customizing messages"
29267 When a message fails to be delivered, or remains on the queue for more than a
29268 configured amount of time, Exim sends a message to the original sender, or
29269 to an alternative configured address. The text of these messages is built into
29270 the code of Exim, but it is possible to change it, either by adding a single
29271 string, or by replacing each of the paragraphs by text supplied in a file.
29273 The &'From:'& and &'To:'& header lines are automatically generated; you can
29274 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
29275 option. Exim also adds the line
29277 Auto-Submitted: auto-generated
29279 to all warning and bounce messages,
29282 .section "Customizing bounce messages"
29283 .cindex "customizing" "bounce message"
29284 .cindex "bounce message" "customizing"
29285 If &%bounce_message_text%& is set, its contents are included in the default
29286 message immediately after &"This message was created automatically by mail
29287 delivery software."& The string is not expanded. It is not used if
29288 &%bounce_message_file%& is set.
29290 When &%bounce_message_file%& is set, it must point to a template file for
29291 constructing error messages. The file consists of a series of text items,
29292 separated by lines consisting of exactly four asterisks. If the file cannot be
29293 opened, default text is used and a message is written to the main and panic
29294 logs. If any text item in the file is empty, default text is used for that
29297 .cindex "&$bounce_recipient$&"
29298 .cindex "&$bounce_return_size_limit$&"
29299 Each item of text that is read from the file is expanded, and there are two
29300 expansion variables which can be of use here: &$bounce_recipient$& is set to
29301 the recipient of an error message while it is being created, and
29302 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
29303 option, rounded to a whole number.
29305 The items must appear in the file in the following order:
29308 The first item is included in the headers, and should include at least a
29309 &'Subject:'& header. Exim does not check the syntax of these headers.
29311 The second item forms the start of the error message. After it, Exim lists the
29312 failing addresses with their error messages.
29314 The third item is used to introduce any text from pipe transports that is to be
29315 returned to the sender. It is omitted if there is no such text.
29317 The fourth item is used to introduce the copy of the message that is returned
29318 as part of the error report.
29320 The fifth item is added after the fourth one if the returned message is
29321 truncated because it is bigger than &%return_size_limit%&.
29323 The sixth item is added after the copy of the original message.
29326 The default state (&%bounce_message_file%& unset) is equivalent to the
29327 following file, in which the sixth item is empty. The &'Subject:'& and some
29328 other lines have been split in order to fit them on the page:
29330 Subject: Mail delivery failed
29331 ${if eq{$sender_address}{$bounce_recipient}
29332 {: returning message to sender}}
29334 This message was created automatically by mail delivery software.
29336 A message ${if eq{$sender_address}{$bounce_recipient}
29337 {that you sent }{sent by
29341 }}could not be delivered to all of its recipients.
29342 The following address(es) failed:
29344 The following text was generated during the delivery attempt(s):
29346 ------ This is a copy of the message, including all the headers.
29349 ------ The body of the message is $message_size characters long;
29351 ------ $bounce_return_size_limit or so are included here.
29354 .section "Customizing warning messages" "SECTcustwarn"
29355 .cindex "customizing" "warning message"
29356 .cindex "warning of delay" "customizing the message"
29357 The option &%warn_message_file%& can be pointed at a template file for use when
29358 warnings about message delays are created. In this case there are only three
29362 The first item is included in the headers, and should include at least a
29363 &'Subject:'& header. Exim does not check the syntax of these headers.
29365 The second item forms the start of the warning message. After it, Exim lists
29366 the delayed addresses.
29368 The third item then ends the message.
29371 The default state is equivalent to the following file, except that some lines
29372 have been split here, in order to fit them on the page:
29374 Subject: Warning: message $message_exim_id delayed
29375 $warn_message_delay
29377 This message was created automatically by mail delivery software.
29379 A message ${if eq{$sender_address}{$warn_message_recipients}
29380 {that you sent }{sent by
29384 }}has not been delivered to all of its recipients after
29385 more than $warn_message_delay on the queue on $primary_hostname.
29387 The message identifier is: $message_exim_id
29388 The subject of the message is: $h_subject
29389 The date of the message is: $h_date
29391 The following address(es) have not yet been delivered:
29393 No action is required on your part. Delivery attempts will
29394 continue for some time, and this warning may be repeated at
29395 intervals if the message remains undelivered. Eventually the
29396 mail delivery software will give up, and when that happens,
29397 the message will be returned to you.
29399 .cindex "&$warn_message_delay$&"
29400 .cindex "&$warn_message_recipients$&"
29401 However, in the default state the subject and date lines are omitted if no
29402 appropriate headers exist. During the expansion of this file,
29403 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
29404 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
29405 of recipients for the warning message. There may be more than one if there are
29406 multiple addresses with different &%errors_to%& settings on the routers that
29412 . ////////////////////////////////////////////////////////////////////////////
29413 . ////////////////////////////////////////////////////////////////////////////
29415 .chapter "Some common configuration settings" "CHAPcomconreq"
29416 This chapter discusses some configuration settings that seem to be fairly
29417 common. More examples and discussion can be found in the Exim book.
29421 .section "Sending mail to a smart host"
29422 .cindex "smart host" "example router"
29423 If you want to send all mail for non-local domains to a &"smart host"&, you
29424 should replace the default &(dnslookup)& router with a router which does the
29425 routing explicitly:
29427 send_to_smart_host:
29428 driver = manualroute
29429 route_list = !+local_domains smart.host.name
29430 transport = remote_smtp
29432 You can use the smart host's IP address instead of the name if you wish.
29433 If you are using Exim only to submit messages to a smart host, and not for
29434 receiving incoming messages, you can arrange for it to do the submission
29435 synchronously by setting the &%mua_wrapper%& option (see chapter
29436 &<<CHAPnonqueueing>>&).
29441 .section "Using Exim to handle mailing lists" "SECTmailinglists"
29442 .cindex "mailing lists"
29443 Exim can be used to run simple mailing lists, but for large and/or complicated
29444 requirements, the use of additional specialized mailing list software such as
29445 Majordomo or Mailman is recommended.
29447 The &(redirect)& router can be used to handle mailing lists where each list
29448 is maintained in a separate file, which can therefore be managed by an
29449 independent manager. The &%domains%& router option can be used to run these
29450 lists in a separate domain from normal mail. For example:
29454 domains = lists.example
29455 file = /usr/lists/$local_part
29458 errors_to = $local_part-request@lists.example
29461 This router is skipped for domains other than &'lists.example'&. For addresses
29462 in that domain, it looks for a file that matches the local part. If there is no
29463 such file, the router declines, but because &%no_more%& is set, no subsequent
29464 routers are tried, and so the whole delivery fails.
29466 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
29467 expanded into a file name or a pipe delivery, which is usually inappropriate in
29470 .cindex "&%errors_to%&"
29471 The &%errors_to%& option specifies that any delivery errors caused by addresses
29472 taken from a mailing list are to be sent to the given address rather than the
29473 original sender of the message. However, before acting on this, Exim verifies
29474 the error address, and ignores it if verification fails.
29476 For example, using the configuration above, mail sent to
29477 &'dicts@lists.example'& is passed on to those addresses contained in
29478 &_/usr/lists/dicts_&, with error reports directed to
29479 &'dicts-request@lists.example'&, provided that this address can be verified.
29480 There could be a file called &_/usr/lists/dicts-request_& containing
29481 the address(es) of this particular list's manager(s), but other approaches,
29482 such as setting up an earlier router (possibly using the &%local_part_prefix%&
29483 or &%local_part_suffix%& options) to handle addresses of the form
29484 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
29488 .section "Syntax errors in mailing lists"
29489 .cindex "mailing lists" "syntax errors in"
29490 If an entry in redirection data contains a syntax error, Exim normally defers
29491 delivery of the original address. That means that a syntax error in a mailing
29492 list holds up all deliveries to the list. This may not be appropriate when a
29493 list is being maintained automatically from data supplied by users, and the
29494 addresses are not rigorously checked.
29496 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
29497 entries that fail to parse, noting the incident in the log. If in addition
29498 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
29499 whenever a broken address is skipped. It is usually appropriate to set
29500 &%syntax_errors_to%& to the same address as &%errors_to%&.
29504 .section "Re-expansion of mailing lists"
29505 .cindex "mailing lists" "re-expansion of"
29506 Exim remembers every individual address to which a message has been delivered,
29507 in order to avoid duplication, but it normally stores only the original
29508 recipient addresses with a message. If all the deliveries to a mailing list
29509 cannot be done at the first attempt, the mailing list is re-expanded when the
29510 delivery is next tried. This means that alterations to the list are taken into
29511 account at each delivery attempt, so addresses that have been added to
29512 the list since the message arrived will therefore receive a copy of the
29513 message, even though it pre-dates their subscription.
29515 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
29516 on the &(redirect)& router. If this is done, any addresses generated by the
29517 router that fail to deliver at the first attempt are added to the message as
29518 &"top level"& addresses, and the parent address that generated them is marked
29519 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
29520 subsequent delivery attempts. The disadvantage of this is that if any of the
29521 failing addresses are incorrect, correcting them in the file has no effect on
29522 pre-existing messages.
29524 The original top-level address is remembered with each of the generated
29525 addresses, and is output in any log messages. However, any intermediate parent
29526 addresses are not recorded. This makes a difference to the log only if the
29527 &%all_parents%& selector is set, but for mailing lists there is normally only
29528 one level of expansion anyway.
29532 .section "Closed mailing lists"
29533 .cindex "mailing lists" "closed"
29534 The examples so far have assumed open mailing lists, to which anybody may
29535 send mail. It is also possible to set up closed lists, where mail is accepted
29536 from specified senders only. This is done by making use of the generic
29537 &%senders%& option to restrict the router that handles the list.
29539 The following example uses the same file as a list of recipients and as a list
29540 of permitted senders. It requires three routers:
29544 domains = lists.example
29545 local_part_suffix = -request
29546 file = /usr/lists/$local_part$local_part_suffix
29551 domains = lists.example
29552 senders = ${if exists {/usr/lists/$local_part}\
29553 {lsearch;/usr/lists/$local_part}{*}}
29554 file = /usr/lists/$local_part
29557 errors_to = $local_part-request@lists.example
29562 domains = lists.example
29564 data = :fail: $local_part@lists.example is a closed mailing list
29566 All three routers have the same &%domains%& setting, so for any other domains,
29567 they are all skipped. The first router runs only if the local part ends in
29568 &%-request%&. It handles messages to the list manager(s) by means of an open
29571 The second router runs only if the &%senders%& precondition is satisfied. It
29572 checks for the existence of a list that corresponds to the local part, and then
29573 checks that the sender is on the list by means of a linear search. It is
29574 necessary to check for the existence of the file before trying to search it,
29575 because otherwise Exim thinks there is a configuration error. If the file does
29576 not exist, the expansion of &%senders%& is *, which matches all senders. This
29577 means that the router runs, but because there is no list, declines, and
29578 &%no_more%& ensures that no further routers are run. The address fails with an
29579 &"unrouteable address"& error.
29581 The third router runs only if the second router is skipped, which happens when
29582 a mailing list exists, but the sender is not on it. This router forcibly fails
29583 the address, giving a suitable error message.
29589 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
29591 .cindex "Variable Envelope Return Paths"
29592 .cindex "envelope sender"
29593 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
29594 are a way of helping mailing list administrators discover which subscription
29595 address is the cause of a particular delivery failure. The idea is to encode
29596 the original recipient address in the outgoing envelope sender address, so that
29597 if the message is forwarded by another host and then subsequently bounces, the
29598 original recipient can be extracted from the recipient address of the bounce.
29600 .oindex &%errors_to%&
29601 .oindex &%return_path%&
29602 Envelope sender addresses can be modified by Exim using two different
29603 facilities: the &%errors_to%& option on a router (as shown in previous mailing
29604 list examples), or the &%return_path%& option on a transport. The second of
29605 these is effective only if the message is successfully delivered to another
29606 host; it is not used for errors detected on the local host (see the description
29607 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
29608 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
29614 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
29615 {$1-request=$local_part%$domain@your.dom.example}fail}
29617 This has the effect of rewriting the return path (envelope sender) on outgoing
29618 SMTP messages, if the local part of the original return path ends in
29619 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
29620 local part and domain of the recipient into the return path. Suppose, for
29621 example, that a message whose return path has been set to
29622 &'somelist-request@your.dom.example'& is sent to
29623 &'subscriber@other.dom.example'&. In the transport, the return path is
29626 somelist-request=subscriber%other.dom.example@your.dom.example
29628 .cindex "&$local_part$&"
29629 For this to work, you must also arrange for outgoing messages that have
29630 &"-request"& in their return paths to have just a single recipient. That is
29631 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
29632 might be sent to several different recipients in the same domain, in which case
29633 &$local_part$& is not available in the transport, because it is not unique.
29635 Unless your host is doing nothing but mailing list deliveries, you should
29636 probably use a separate transport for the VERP deliveries, so as not to use
29637 extra resources for the others. This can easily be done by expanding the
29638 &%transport%& option in the router:
29642 domains = ! +local_domains
29644 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
29645 {verp_smtp}{remote_smtp}}
29648 If you want to change the return path using &%errors_to%& in a router instead
29649 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
29650 routers that handle mailing list addresses. This will ensure that all delivery
29651 errors, including those detected on the local host, are sent to the VERP
29654 On a host that does no local deliveries and has no manual routing, only the
29655 &(dnslookup)& router needs to be changed. A special transport is not needed for
29656 SMTP deliveries. Every mailing list recipient has its own return path value,
29657 and so Exim must hand them to the transport one at a time. Here is an example
29658 of a &(dnslookup)& router that implements VERP:
29662 domains = ! +local_domains
29663 transport = remote_smtp
29665 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
29666 {$1-request=$local_part%$domain@your.dom.example}fail}
29669 Before you start sending out messages with VERPed return paths, you must also
29670 configure Exim to accept the bounce messages that come back to those paths.
29671 Typically this is done by setting a &%local_part_suffix%& option for a
29672 router, and using this to route the messages to wherever you want to handle
29675 The overhead incurred in using VERP depends very much on the size of the
29676 message, the number of recipient addresses that resolve to the same remote
29677 host, and the speed of the connection over which the message is being sent. If
29678 a lot of addresses resolve to the same host and the connection is slow, sending
29679 a separate copy of the message for each address may take substantially longer
29680 than sending a single copy with many recipients (for which VERP cannot be
29689 .section "Virtual domains" "SECTvirtualdomains"
29690 .cindex "virtual domains"
29691 .cindex "domain" "virtual"
29692 The phrase &'virtual domain'& is unfortunately used with two rather different
29696 A domain for which there are no real mailboxes; all valid local parts are
29697 aliases for other email addresses. Common examples are organizational
29698 top-level domains and &"vanity"& domains.
29700 One of a number of independent domains that are all handled by the same host,
29701 with mailboxes on that host, but where the mailbox owners do not necessarily
29702 have login accounts on that host.
29705 The first usage is probably more common, and does seem more &"virtual"& than
29706 the second. This kind of domain can be handled in Exim with a straightforward
29707 aliasing router. One approach is to create a separate alias file for each
29708 virtual domain. Exim can test for the existence of the alias file to determine
29709 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
29710 to a router of this form:
29714 domains = dsearch;/etc/mail/virtual
29715 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
29718 The &%domains%& option specifies that the router is to be skipped, unless there
29719 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
29720 domain that is being processed. When the router runs, it looks up the local
29721 part in the file to find a new address (or list of addresses). The &%no_more%&
29722 setting ensures that if the lookup fails (leading to &%data%& being an empty
29723 string), Exim gives up on the address without trying any subsequent routers.
29725 This one router can handle all the virtual domains because the alias file names
29726 follow a fixed pattern. Permissions can be arranged so that appropriate people
29727 can edit the different alias files. A successful aliasing operation results in
29728 a new envelope recipient address, which is then routed from scratch.
29730 The other kind of &"virtual"& domain can also be handled in a straightforward
29731 way. One approach is to create a file for each domain containing a list of
29732 valid local parts, and use it in a router like this:
29736 domains = dsearch;/etc/mail/domains
29737 local_parts = lsearch;/etc/mail/domains/$domain
29738 transport = my_mailboxes
29740 The address is accepted if there is a file for the domain, and the local part
29741 can be found in the file. The &%domains%& option is used to check for the
29742 file's existence because &%domains%& is tested before the &%local_parts%&
29743 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
29744 because that option is tested after &%local_parts%&. The transport is as
29748 driver = appendfile
29749 file = /var/mail/$domain/$local_part
29752 This uses a directory of mailboxes for each domain. The &%user%& setting is
29753 required, to specify which uid is to be used for writing to the mailboxes.
29755 The configuration shown here is just one example of how you might support this
29756 requirement. There are many other ways this kind of configuration can be set
29757 up, for example, by using a database instead of separate files to hold all the
29758 information about the domains.
29762 .section "Multiple user mailboxes" "SECTmulbox"
29763 .cindex "multiple mailboxes"
29764 .cindex "mailbox" "multiple"
29765 .cindex "local part" "prefix"
29766 .cindex "local part" "suffix"
29767 Heavy email users often want to operate with multiple mailboxes, into which
29768 incoming mail is automatically sorted. A popular way of handling this is to
29769 allow users to use multiple sender addresses, so that replies can easily be
29770 identified. Users are permitted to add prefixes or suffixes to their local
29771 parts for this purpose. The wildcard facility of the generic router options
29772 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
29773 example, consider this router:
29778 file = $home/.forward
29779 local_part_suffix = -*
29780 local_part_suffix_optional
29783 .cindex "&$local_part_suffix$&"
29784 It runs a user's &_.forward_& file for all local parts of the form
29785 &'username-*'&. Within the filter file the user can distinguish different
29786 cases by testing the variable &$local_part_suffix$&. For example:
29788 if $local_part_suffix contains -special then
29789 save /home/$local_part/Mail/special
29792 If the filter file does not exist, or does not deal with such addresses, they
29793 fall through to subsequent routers, and, assuming no subsequent use of the
29794 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
29795 control over which suffixes are valid.
29797 Alternatively, a suffix can be used to trigger the use of a different
29798 &_.forward_& file &-- which is the way a similar facility is implemented in
29804 file = $home/.forward$local_part_suffix
29805 local_part_suffix = -*
29806 local_part_suffix_optional
29809 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
29810 example, &_.forward-special_& is used. Once again, if the appropriate file
29811 does not exist, or does not deal with the address, it is passed on to
29812 subsequent routers, which could, if required, look for an unqualified
29813 &_.forward_& file to use as a default.
29817 .section "Simplified vacation processing"
29818 .cindex "vacation processing"
29819 The traditional way of running the &'vacation'& program is for a user to set up
29820 a pipe command in a &_.forward_& file
29821 (see section &<<SECTspecitredli>>& for syntax details).
29822 This is prone to error by inexperienced users. There are two features of Exim
29823 that can be used to make this process simpler for users:
29826 A local part prefix such as &"vacation-"& can be specified on a router which
29827 can cause the message to be delivered directly to the &'vacation'& program, or
29828 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
29829 &_.forward_& file are then much simpler. For example:
29831 spqr, vacation-spqr
29834 The &%require_files%& generic router option can be used to trigger a
29835 vacation delivery by checking for the existence of a certain file in the
29836 user's home directory. The &%unseen%& generic option should also be used, to
29837 ensure that the original delivery also proceeds. In this case, all the user has
29838 to do is to create a file called, say, &_.vacation_&, containing a vacation
29842 Another advantage of both these methods is that they both work even when the
29843 use of arbitrary pipes by users is locked out.
29847 .section "Taking copies of mail"
29848 .cindex "message" "copying every"
29849 Some installations have policies that require archive copies of all messages to
29850 be made. A single copy of each message can easily be taken by an appropriate
29851 command in a system filter, which could, for example, use a different file for
29852 each day's messages.
29854 There is also a shadow transport mechanism that can be used to take copies of
29855 messages that are successfully delivered by local transports, one copy per
29856 delivery. This could be used, &'inter alia'&, to implement automatic
29857 notification of delivery by sites that insist on doing such things.
29861 .section "Intermittently connected hosts"
29862 .cindex "intermittently connected hosts"
29863 It has become quite common (because it is cheaper) for hosts to connect to the
29864 Internet periodically rather than remain connected all the time. The normal
29865 arrangement is that mail for such hosts accumulates on a system that is
29866 permanently connected.
29868 Exim was designed for use on permanently connected hosts, and so it is not
29869 particularly well-suited to use in an intermittently connected environment.
29870 Nevertheless there are some features that can be used.
29873 .section "Exim on the upstream server host"
29874 It is tempting to arrange for incoming mail for the intermittently connected
29875 host to remain on Exim's queue until the client connects. However, this
29876 approach does not scale very well. Two different kinds of waiting message are
29877 being mixed up in the same queue &-- those that cannot be delivered because of
29878 some temporary problem, and those that are waiting for their destination host
29879 to connect. This makes it hard to manage the queue, as well as wasting
29880 resources, because each queue runner scans the entire queue.
29882 A better approach is to separate off those messages that are waiting for an
29883 intermittently connected host. This can be done by delivering these messages
29884 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
29885 format, from where they are transmitted by other software when their
29886 destination connects. This makes it easy to collect all the mail for one host
29887 in a single directory, and to apply local timeout rules on a per-message basis
29890 On a very small scale, leaving the mail on Exim's queue can be made to work. If
29891 you are doing this, you should configure Exim with a long retry period for the
29892 intermittent host. For example:
29894 cheshire.wonderland.fict.example * F,5d,24h
29896 This stops a lot of failed delivery attempts from occurring, but Exim remembers
29897 which messages it has queued up for that host. Once the intermittent host comes
29898 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
29899 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
29900 causes all the queued up messages to be delivered, often down a single SMTP
29901 connection. While the host remains connected, any new messages get delivered
29904 If the connecting hosts do not have fixed IP addresses, that is, if a host is
29905 issued with a different IP address each time it connects, Exim's retry
29906 mechanisms on the holding host get confused, because the IP address is normally
29907 used as part of the key string for holding retry information. This can be
29908 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
29909 Since this has disadvantages for permanently connected hosts, it is best to
29910 arrange a separate transport for the intermittently connected ones.
29914 .section "Exim on the intermittently connected client host"
29915 The value of &%smtp_accept_queue_per_connection%& should probably be
29916 increased, or even set to zero (that is, disabled) on the intermittently
29917 connected host, so that all incoming messages down a single connection get
29918 delivered immediately.
29920 .cindex "SMTP" "passed connection"
29921 .cindex "SMTP" "multiple deliveries"
29922 .cindex "multiple SMTP deliveries"
29923 Mail waiting to be sent from an intermittently connected host will probably
29924 not have been routed, because without a connection DNS lookups are not
29925 possible. This means that if a normal queue run is done at connection time,
29926 each message is likely to be sent in a separate SMTP session. This can be
29927 avoided by starting the queue run with a command line option beginning with
29928 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
29929 first pass, routing is done but no deliveries take place. The second pass is a
29930 normal queue run; since all the messages have been previously routed, those
29931 destined for the same host are likely to get sent as multiple deliveries in a
29932 single SMTP connection.
29936 . ////////////////////////////////////////////////////////////////////////////
29937 . ////////////////////////////////////////////////////////////////////////////
29939 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
29940 "Exim as a non-queueing client"
29941 .cindex "client" "non-queueing"
29942 .cindex "smart host" "queueing; suppressing"
29943 On a personal computer, it is a common requirement for all
29944 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
29945 configured to operate that way, for all the popular operating systems.
29946 However, there are some MUAs for Unix-like systems that cannot be so
29947 configured: they submit messages using the command line interface of
29948 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
29951 If the personal computer runs continuously, there is no problem, because it can
29952 run a conventional MTA that handles delivery to the smart host, and deal with
29953 any delays via its queueing mechanism. However, if the computer does not run
29954 continuously or runs different operating systems at different times, queueing
29955 email is not desirable.
29957 There is therefore a requirement for something that can provide the
29958 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
29959 any queueing or retrying facilities. Furthermore, the delivery to the smart
29960 host should be synchronous, so that if it fails, the sending MUA is immediately
29961 informed. In other words, we want something that extends an MUA that submits
29962 to a local MTA via the command line so that it behaves like one that submits
29963 to a remote smart host using TCP/SMTP.
29965 There are a number of applications (for example, there is one called &'ssmtp'&)
29966 that do this job. However, people have found them to be lacking in various
29967 ways. For instance, you might want to allow aliasing and forwarding to be done
29968 before sending a message to the smart host.
29970 Exim already had the necessary infrastructure for doing this job. Just a few
29971 tweaks were needed to make it behave as required, though it is somewhat of an
29972 overkill to use a fully-featured MTA for this purpose.
29974 .cindex "&%mua_wrapper%&"
29975 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
29976 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
29977 assumes that it is being used to &"wrap"& a command-line MUA in the manner
29978 just described. As well as setting &%mua_wrapper%&, you also need to provide a
29979 compatible router and transport configuration. Typically there will be just one
29980 router and one transport, sending everything to a smart host.
29982 When run in MUA wrapping mode, the behaviour of Exim changes in the
29986 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
29987 In other words, the only way to submit messages is via the command line.
29989 Each message is synchonously delivered as soon as it is received (&%-odi%& is
29990 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
29991 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
29992 does not finish until the delivery attempt is complete. If the delivery is
29993 successful, a zero return code is given.
29995 Address redirection is permitted, but the final routing for all addresses must
29996 be to the same remote transport, and to the same list of hosts. Furthermore,
29997 the return address (envelope sender) must be the same for all recipients, as
29998 must any added or deleted header lines. In other words, it must be possible to
29999 deliver the message in a single SMTP transaction, however many recipients there
30002 If these conditions are not met, or if routing any address results in a
30003 failure or defer status, or if Exim is unable to deliver all the recipients
30004 successfully to one of the smart hosts, delivery of the entire message fails.
30006 Because no queueing is allowed, all failures are treated as permanent; there
30007 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
30008 smart host. Furthermore, because only a single yes/no response can be given to
30009 the caller, it is not possible to deliver to some recipients and not others. If
30010 there is an error (temporary or permanent) for any recipient, all are failed.
30012 If more than one smart host is listed, Exim will try another host after a
30013 connection failure or a timeout, in the normal way. However, if this kind of
30014 failure happens for all the hosts, the delivery fails.
30016 When delivery fails, an error message is written to the standard error stream
30017 (as well as to Exim's log), and Exim exits to the caller with a return code
30018 value 1. The message is expunged from Exim's spool files. No bounce messages
30019 are ever generated.
30021 No retry data is maintained, and any retry rules are ignored.
30023 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
30024 true, &%max_rcpt%& in the smtp transport is forced to &"unlimited"&,
30025 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
30028 The overall effect is that Exim makes a single synchronous attempt to deliver
30029 the message, failing if there is any kind of problem. Because no local
30030 deliveries are done and no daemon can be run, Exim does not need root
30031 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
30032 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
30033 the advantages and disadvantages of running without root privilege.
30038 . ////////////////////////////////////////////////////////////////////////////
30039 . ////////////////////////////////////////////////////////////////////////////
30041 .chapter "Log files" "CHAPlog"
30042 .scindex IIDloggen "log" "general description"
30043 .cindex "log" "types of"
30044 Exim writes three different logs, referred to as the main log, the reject log,
30049 The main log records the arrival of each message and each delivery in a single
30050 line in each case. The format is as compact as possible, in an attempt to keep
30051 down the size of log files. Two-character flag sequences make it easy to pick
30052 out these lines. A number of other events are recorded in the main log. Some of
30053 them are optional, in which case the &%log_selector%& option controls whether
30054 they are included or not. A Perl script called &'eximstats'&, which does simple
30055 analysis of main log files, is provided in the Exim distribution (see section
30056 &<<SECTmailstat>>&).
30058 .cindex "reject log"
30059 The reject log records information from messages that are rejected as a result
30060 of a configuration option (that is, for policy reasons).
30061 The first line of each rejection is a copy of the line that is also written to
30062 the main log. Then, if the message's header has been read at the time the log
30063 is written, its contents are written to this log. Only the original header
30064 lines are available; header lines added by ACLs are not logged. You can use the
30065 reject log to check that your policy controls are working correctly; on a busy
30066 host this may be easier than scanning the main log for rejection messages. You
30067 can suppress the writing of the reject log by setting &%write_rejectlog%&
30070 .cindex "panic log"
30071 .cindex "system log"
30072 When certain serious errors occur, Exim writes entries to its panic log. If the
30073 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
30074 are usually written to the main log as well, but can get lost amid the mass of
30075 other entries. The panic log should be empty under normal circumstances. It is
30076 therefore a good idea to check it (or to have a &'cron'& script check it)
30077 regularly, in order to become aware of any problems. When Exim cannot open its
30078 panic log, it tries as a last resort to write to the system log (syslog). This
30079 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
30080 message itself is written at priority LOG_CRIT.
30083 Every log line starts with a timestamp, in the format shown in the following
30084 example. Note that many of the examples shown in this chapter are line-wrapped.
30085 In the log file, this would be all on one line:
30087 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
30090 By default, the timestamps are in the local timezone. There are two
30091 ways of changing this:
30094 You can set the &%timezone%& option to a different time zone; in particular, if
30099 the timestamps will be in UTC (aka GMT).
30101 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
30104 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
30111 .section "Where the logs are written" "SECTwhelogwri"
30112 .cindex "log" "destination"
30113 .cindex "log" "to file"
30114 .cindex "log" "to syslog"
30116 The logs may be written to local files, or to syslog, or both. However, it
30117 should be noted that many syslog implementations use UDP as a transport, and
30118 are therefore unreliable in the sense that messages are not guaranteed to
30119 arrive at the loghost, nor is the ordering of messages necessarily maintained.
30120 It has also been reported that on large log files (tens of megabytes) you may
30121 need to tweak syslog to prevent it syncing the file with each write &-- on
30122 Linux this has been seen to make syslog take 90% plus of CPU time.
30124 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
30125 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
30126 configuration. This latter string is expanded, so it can contain, for example,
30127 references to the host name:
30129 log_file_path = /var/log/$primary_hostname/exim_%slog
30131 It is generally advisable, however, to set the string in &_Local/Makefile_&
30132 rather than at run time, because then the setting is available right from the
30133 start of Exim's execution. Otherwise, if there's something it wants to log
30134 before it has read the configuration file (for example, an error in the
30135 configuration file) it will not use the path you want, and may not be able to
30138 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
30139 list, currently limited to at most two items. This is one option where the
30140 facility for changing a list separator may not be used. The list must always be
30141 colon-separated. If an item in the list is &"syslog"& then syslog is used;
30142 otherwise the item must either be an absolute path, containing &`%s`& at the
30143 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
30144 implying the use of a default path.
30146 When Exim encounters an empty item in the list, it searches the list defined by
30147 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
30148 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
30149 mean &"use the path specified at build time"&. It no such item exists, log
30150 files are written in the &_log_& subdirectory of the spool directory. This is
30151 equivalent to the setting:
30153 log_file_path = $spool_directory/log/%slog
30155 If you do not specify anything at build time or run time, that is where the
30158 A log file path may also contain &`%D`& if datestamped log file names are in
30159 use &-- see section &<<SECTdatlogfil>>& below.
30161 Here are some examples of possible settings:
30163 &`LOG_FILE_PATH=syslog `& syslog only
30164 &`LOG_FILE_PATH=:syslog `& syslog and default path
30165 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
30166 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
30168 If there are more than two paths in the list, the first is used and a panic
30173 .section "Logging to local files that are periodically &""cycled""&"
30174 .cindex "log" "cycling local files"
30175 .cindex "cycling logs"
30176 .cindex "&'exicyclog'&"
30177 .cindex "log" "local files; writing to"
30178 Some operating systems provide centralized and standardised methods for cycling
30179 log files. For those that do not, a utility script called &'exicyclog'& is
30180 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
30181 main and reject logs each time it is called. The maximum number of old logs to
30182 keep can be set. It is suggested this script is run as a daily &'cron'& job.
30184 An Exim delivery process opens the main log when it first needs to write to it,
30185 and it keeps the file open in case subsequent entries are required &-- for
30186 example, if a number of different deliveries are being done for the same
30187 message. However, remote SMTP deliveries can take a long time, and this means
30188 that the file may be kept open long after it is renamed if &'exicyclog'& or
30189 something similar is being used to rename log files on a regular basis. To
30190 ensure that a switch of log files is noticed as soon as possible, Exim calls
30191 &[stat()]& on the main log's name before reusing an open file, and if the file
30192 does not exist, or its inode has changed, the old file is closed and Exim
30193 tries to open the main log from scratch. Thus, an old log file may remain open
30194 for quite some time, but no Exim processes should write to it once it has been
30199 .section "Datestamped log files" "SECTdatlogfil"
30200 .cindex "log" "datestamped files"
30201 Instead of cycling the main and reject log files by renaming them
30202 periodically, some sites like to use files whose names contain a datestamp,
30203 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_&.
30204 Exim has support for this way of working. It is enabled by setting the
30205 &%log_file_path%& option to a path that includes &`%D`& at the point where the
30206 datestamp is required. For example:
30208 log_file_path = /var/spool/exim/log/%slog-%D
30209 log_file_path = /var/log/exim-%s-%D.log
30210 log_file_path = /var/spool/exim/log/%D-%slog
30212 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
30213 examples of names generated by the above examples:
30215 /var/spool/exim/log/mainlog-20021225
30216 /var/log/exim-reject-20021225.log
30217 /var/spool/exim/log/20021225-mainlog
30219 When this form of log file is specified, Exim automatically switches to new
30220 files at midnight. It does not make any attempt to compress old logs; you
30221 will need to write your own script if you require this. You should not
30222 run &'exicyclog'& with this form of logging.
30224 The location of the panic log is also determined by &%log_file_path%&, but it
30225 is not datestamped, because rotation of the panic log does not make sense.
30226 When generating the name of the panic log, &`%D`& is removed from the string.
30227 In addition, if it immediately follows a slash, a following non-alphanumeric
30228 character is removed; otherwise a preceding non-alphanumeric character is
30229 removed. Thus, the three examples above would give these panic log names:
30231 /var/spool/exim/log/paniclog
30232 /var/log/exim-panic.log
30233 /var/spool/exim/log/paniclog
30237 .section "Logging to syslog"
30238 .cindex "log" "syslog; writing to"
30239 The use of syslog does not change what Exim logs or the format of its messages,
30240 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
30241 Exim's log lines are omitted when these lines are sent to syslog. Apart from
30242 that, the same strings are written to syslog as to log files. The syslog
30243 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
30244 by default, but you can change these by setting the &%syslog_facility%& and
30245 &%syslog_processname%& options, respectively. If Exim was compiled with
30246 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
30247 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
30248 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
30249 the time and host name to each line.
30250 The three log streams are mapped onto syslog priorities as follows:
30253 &'mainlog'& is mapped to LOG_INFO
30255 &'rejectlog'& is mapped to LOG_NOTICE
30257 &'paniclog'& is mapped to LOG_ALERT
30260 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
30261 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
30262 these are routed by syslog to the same place. You can suppress this duplication
30263 by setting &%syslog_duplication%& false.
30265 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
30266 entries contain multiple lines when headers are included. To cope with both
30267 these cases, entries written to syslog are split into separate &[syslog()]&
30268 calls at each internal newline, and also after a maximum of
30269 870 data characters. (This allows for a total syslog line length of 1024, when
30270 additions such as timestamps are added.) If you are running a syslog
30271 replacement that can handle lines longer than the 1024 characters allowed by
30272 RFC 3164, you should set
30274 SYSLOG_LONG_LINES=yes
30276 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
30277 lines, but it still splits at internal newlines in &'reject'& log entries.
30279 To make it easy to re-assemble split lines later, each component of a split
30280 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
30281 where <&'n'&> is the component number and <&'m'&> is the total number of
30282 components in the entry. The / delimiter is used when the line was split
30283 because it was too long; if it was split because of an internal newline, the \
30284 delimiter is used. For example, supposing the length limit to be 50 instead of
30285 870, the following would be the result of a typical rejection message to
30286 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
30287 name, and pid as added by syslog:
30289 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
30290 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
30291 [3/5] when scanning for sender: missing or malformed lo
30292 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
30295 The same error might cause the following lines to be written to &"rejectlog"&
30298 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
30299 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
30300 [3/18] er when scanning for sender: missing or malformed
30301 [4/18] local part in "<>" (envelope sender is <ph10@cam
30303 [6\18] Recipients: ph10@some.domain.cam.example
30304 [7\18] P Received: from [127.0.0.1] (ident=ph10)
30305 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
30306 [9\18] id 16RdAL-0006pc-00
30307 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
30308 [11\18] 09:43 +0100
30310 [13\18] Subject: this is a test header
30311 [18\18] X-something: this is another header
30312 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
30315 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
30317 Log lines that are neither too long nor contain newlines are written to syslog
30318 without modification.
30320 If only syslog is being used, the Exim monitor is unable to provide a log tail
30321 display, unless syslog is routing &'mainlog'& to a file on the local host and
30322 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
30327 .section "Log line flags"
30328 One line is written to the main log for each message received, and for each
30329 successful, unsuccessful, and delayed delivery. These lines can readily be
30330 picked out by the distinctive two-character flags that immediately follow the
30331 timestamp. The flags are:
30333 &`<=`& message arrival
30334 &`=>`& normal message delivery
30335 &`->`& additional address in same delivery
30336 &`*>`& delivery suppressed by &%-N%&
30337 &`**`& delivery failed; address bounced
30338 &`==`& delivery deferred; temporary problem
30342 .section "Logging message reception"
30343 .cindex "log" "reception line"
30344 The format of the single-line entry in the main log that is written for every
30345 message received is shown in the basic example below, which is split over
30346 several lines in order to fit it on the page:
30348 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
30349 H=mailer.fict.example [192.168.123.123] U=exim
30350 P=smtp S=5678 id=<incoming message id>
30352 The address immediately following &"<="& is the envelope sender address. A
30353 bounce message is shown with the sender address &"<>"&, and if it is locally
30354 generated, this is followed by an item of the form
30358 which is a reference to the message that caused the bounce to be sent.
30362 For messages from other hosts, the H and U fields identify the remote host and
30363 record the RFC 1413 identity of the user that sent the message, if one was
30364 received. The number given in square brackets is the IP address of the sending
30365 host. If there is a single, unparenthesized host name in the H field, as
30366 above, it has been verified to correspond to the IP address (see the
30367 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
30368 by the remote host in the SMTP HELO or EHLO command, and has not been
30369 verified. If verification yields a different name to that given for HELO or
30370 EHLO, the verified name appears first, followed by the HELO or EHLO
30371 name in parentheses.
30373 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
30374 without brackets, in the HELO or EHLO command, leading to entries in
30375 the log containing text like these examples:
30377 H=(10.21.32.43) [192.168.8.34]
30378 H=([10.21.32.43]) [192.168.8.34]
30380 This can be confusing. Only the final address in square brackets can be relied
30383 For locally generated messages (that is, messages not received over TCP/IP),
30384 the H field is omitted, and the U field contains the login name of the caller
30387 .cindex "authentication" "logging"
30388 .cindex "AUTH" "logging"
30389 For all messages, the P field specifies the protocol used to receive the
30390 message. This is the value that is stored in &$received_protocol$&. In the case
30391 of incoming SMTP messages, the value indicates whether or not any SMTP
30392 extensions (ESMTP), encryption, or authentication were used. If the SMTP
30393 session was encrypted, there is an additional X field that records the cipher
30394 suite that was used.
30396 The protocol is set to &"esmptsa"& or &"esmtpa"& for messages received from
30397 hosts that have authenticated themselves using the SMTP AUTH command. The first
30398 value is used when the SMTP connection was encrypted (&"secure"&). In this case
30399 there is an additional item A= followed by the name of the authenticator that
30400 was used. If an authenticated identification was set up by the authenticator's
30401 &%server_set_id%& option, this is logged too, separated by a colon from the
30402 authenticator name.
30404 .cindex "size" "of message"
30405 The id field records the existing message id, if present. The size of the
30406 received message is given by the S field. When the message is delivered,
30407 headers may be removed or added, so that the size of delivered copies of the
30408 message may not correspond with this value (and indeed may be different to each
30411 The &%log_selector%& option can be used to request the logging of additional
30412 data when a message is received. See section &<<SECTlogselector>>& below.
30416 .section "Logging deliveries"
30417 .cindex "log" "delivery line"
30418 The format of the single-line entry in the main log that is written for every
30419 delivery is shown in one of the examples below, for local and remote
30420 deliveries, respectively. Each example has been split into two lines in order
30421 to fit it on the page:
30423 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
30424 <marv@hitch.fict.example> R=localuser T=local_delivery
30425 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
30426 monk@holistic.fict.example R=dnslookup T=remote_smtp
30427 H=holistic.fict.example [192.168.234.234]
30429 For ordinary local deliveries, the original address is given in angle brackets
30430 after the final delivery address, which might be a pipe or a file. If
30431 intermediate address(es) exist between the original and the final address, the
30432 last of these is given in parentheses after the final address. The R and T
30433 fields record the router and transport that were used to process the address.
30435 If a shadow transport was run after a successful local delivery, the log line
30436 for the successful delivery has an item added on the end, of the form
30438 &`ST=<`&&'shadow transport name'&&`>`&
30440 If the shadow transport did not succeed, the error message is put in
30441 parentheses afterwards.
30443 .cindex "asterisk" "after IP address"
30444 When more than one address is included in a single delivery (for example, two
30445 SMTP RCPT commands in one transaction) the second and subsequent addresses are
30446 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
30447 down a single SMTP connection, an asterisk follows the IP address in the log
30448 lines for the second and subsequent messages.
30450 The generation of a reply message by a filter file gets logged as a
30451 &"delivery"& to the addressee, preceded by &">"&.
30453 The &%log_selector%& option can be used to request the logging of additional
30454 data when a message is delivered. See section &<<SECTlogselector>>& below.
30457 .section "Discarded deliveries"
30458 .cindex "discarded messages"
30459 .cindex "message" "discarded"
30460 .cindex "delivery" "discarded; logging"
30461 When a message is discarded as a result of the command &"seen finish"& being
30462 obeyed in a filter file which generates no deliveries, a log entry of the form
30464 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
30465 <low.club@bridge.example> R=userforward
30467 is written, to record why no deliveries are logged. When a message is discarded
30468 because it is aliased to &":blackhole:"& the log line is like this:
30470 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
30471 <hole@nowhere.example> R=blackhole_router
30475 .section "Deferred deliveries"
30476 When a delivery is deferred, a line of the following form is logged:
30478 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
30479 R=dnslookup T=smtp defer (146): Connection refused
30481 In the case of remote deliveries, the error is the one that was given for the
30482 last IP address that was tried. Details of individual SMTP failures are also
30483 written to the log, so the above line would be preceded by something like
30485 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
30486 mail1.endrest.example [192.168.239.239]: Connection refused
30488 When a deferred address is skipped because its retry time has not been reached,
30489 a message is written to the log, but this can be suppressed by setting an
30490 appropriate value in &%log_selector%&.
30494 .section "Delivery failures"
30495 .cindex "delivery" "failure; logging"
30496 If a delivery fails because an address cannot be routed, a line of the
30497 following form is logged:
30499 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
30500 <jim@trek99.example>: unknown mail domain
30502 If a delivery fails at transport time, the router and transport are shown, and
30503 the response from the remote host is included, as in this example:
30505 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
30506 R=dnslookup T=remote_smtp: SMTP error from remote mailer
30507 after pipelined RCPT TO:<ace400@pb.example>: host
30508 pbmail3.py.example [192.168.63.111]: 553 5.3.0
30509 <ace400@pb.example>...Addressee unknown
30511 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
30512 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
30513 disabling PIPELINING. The log lines for all forms of delivery failure are
30514 flagged with &`**`&.
30518 .section "Fake deliveries"
30519 .cindex "delivery" "fake; logging"
30520 If a delivery does not actually take place because the &%-N%& option has been
30521 used to suppress it, a normal delivery line is written to the log, except that
30522 &"=>"& is replaced by &"*>"&.
30526 .section "Completion"
30529 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
30531 is written to the main log when a message is about to be removed from the spool
30532 at the end of its processing.
30537 .section "Summary of Fields in Log Lines"
30538 .cindex "log" "summary of fields"
30539 A summary of the field identifiers that are used in log lines is shown in
30540 the following table:
30542 &`A `& authenticator name (and optional id)
30543 &`C `& SMTP confirmation on delivery
30544 &`CV `& certificate verification status
30545 &`DN `& distinguished name from peer certificate
30546 &`DT `& on &`=>`& lines: time taken for a delivery
30547 &`F `& sender address (on delivery lines)
30548 &`H `& host name and IP address
30549 &`I `& local interface used
30550 &`id `& message id for incoming message
30551 &`P `& on &`<=`& lines: protocol used
30552 &` `& on &`=>`& and &`**`& lines: return path
30553 &`QT `& on &`=>`& lines: time spent on queue so far
30554 &` `& on &"Completed"& lines: time spent on queue
30555 &`R `& on &`<=`& lines: reference for local bounce
30556 &` `& on &`=>`& &`**`& and &`==`& lines: router name
30557 &`S `& size of message
30558 &`ST `& shadow transport name
30559 &`T `& on &`<=`& lines: message subject (topic)
30560 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
30561 &`U `& local user or RFC 1413 identity
30562 &`X `& TLS cipher suite
30566 .section "Other log entries"
30567 Various other types of log entry are written from time to time. Most should be
30568 self-explanatory. Among the more common are:
30571 .cindex "retry" "time not reached"
30572 &'retry time not reached'&&~&~An address previously suffered a temporary error
30573 during routing or local delivery, and the time to retry has not yet arrived.
30574 This message is not written to an individual message log file unless it happens
30575 during the first delivery attempt.
30577 &'retry time not reached for any host'&&~&~An address previously suffered
30578 temporary errors during remote delivery, and the retry time has not yet arrived
30579 for any of the hosts to which it is routed.
30581 .cindex "spool directory" "file locked"
30582 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
30583 some other Exim process is already working on the message. This can be quite
30584 common if queue running processes are started at frequent intervals. The
30585 &'exiwhat'& utility script can be used to find out what Exim processes are
30588 .cindex "error" "ignored"
30589 &'error ignored'&&~&~There are several circumstances that give rise to this
30592 Exim failed to deliver a bounce message whose age was greater than
30593 &%ignore_bounce_errors_after%&. The bounce was discarded.
30595 A filter file set up a delivery using the &"noerror"& option, and the delivery
30596 failed. The delivery was discarded.
30598 A delivery set up by a router configured with
30599 . ==== As this is a nested list, any displays it contains must be indented
30600 . ==== as otherwise they are too far to the left.
30604 failed. The delivery was discarded.
30612 .section "Reducing or increasing what is logged" "SECTlogselector"
30613 .cindex "log" "selectors"
30614 By setting the &%log_selector%& global option, you can disable some of Exim's
30615 default logging, or you can request additional logging. The value of
30616 &%log_selector%& is made up of names preceded by plus or minus characters. For
30619 log_selector = +arguments -retry_defer
30621 The list of optional log items is in the following table, with the default
30622 selection marked by asterisks:
30624 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
30625 &` address_rewrite `& address rewriting
30626 &` all_parents `& all parents in => lines
30627 &` arguments `& command line arguments
30628 &`*connection_reject `& connection rejections
30629 &`*delay_delivery `& immediate delivery delayed
30630 &` deliver_time `& time taken to perform delivery
30631 &` delivery_size `& add &`S=`&&'nnn'& to => lines
30632 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
30633 &`*etrn `& ETRN commands
30634 &`*host_lookup_failed `& as it says
30635 &` ident_timeout `& timeout for ident connection
30636 &` incoming_interface `& incoming interface on <= lines
30637 &` incoming_port `& incoming port on <= lines
30638 &`*lost_incoming_connection `& as it says (includes timeouts)
30639 &` outgoing_port `& add remote port to => lines
30640 &`*queue_run `& start and end queue runs
30641 &` queue_time `& time on queue for one recipient
30642 &` queue_time_overall `& time on queue for whole message
30643 &` received_recipients `& recipients on <= lines
30644 &` received_sender `& sender on <= lines
30645 &`*rejected_header `& header contents on reject log
30646 &`*retry_defer `& &"retry time not reached"&
30647 &` return_path_on_delivery `& put return path on => and *\ lines
30648 &` sender_on_delivery `& add sender to => lines
30649 &`*sender_verify_fail `& sender verification failures
30650 &`*size_reject `& rejection because too big
30651 &`*skip_delivery `& delivery skipped in a queue run
30652 &` smtp_confirmation `& SMTP confirmation on => lines
30653 &` smtp_connection `& SMTP connections
30654 &` smtp_incomplete_transaction`& incomplete SMTP transactions
30655 &` smtp_protocol_error `& SMTP protocol errors
30656 &` smtp_syntax_error `& SMTP syntax errors
30657 &` subject `& contents of &'Subject:'& on <= lines
30658 &` tls_certificate_verified `& certificate verification status
30659 &`*tls_cipher `& TLS cipher suite on <= and => lines
30660 &` tls_peerdn `& TLS peer DN on <= and => lines
30661 &` unknown_in_list `& DNS lookup failed in list match
30663 &` all `& all of the above
30665 More details on each of these items follows:
30668 .cindex "&%warn%& statement" "log when skipping"
30669 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
30670 its conditions cannot be evaluated, a log line to this effect is written if
30671 this log selector is set.
30673 .cindex "log" "rewriting"
30674 .cindex "rewriting" "logging"
30675 &%address_rewrite%&: This applies both to global rewrites and per-transport
30676 rewrites, but not to rewrites in filters run as an unprivileged user (because
30677 such users cannot access the log).
30679 .cindex "log" "full parentage"
30680 &%all_parents%&: Normally only the original and final addresses are logged on
30681 delivery lines; with this selector, intermediate parents are given in
30682 parentheses between them.
30684 .cindex "log" "Exim arguments"
30685 .cindex "Exim arguments" "logging"
30686 &%arguments%&: This causes Exim to write the arguments with which it was called
30687 to the main log, preceded by the current working directory. This is a debugging
30688 feature, added to make it easier to find out how certain MUAs call
30689 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
30690 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
30691 that are empty or that contain white space are quoted. Non-printing characters
30692 are shown as escape sequences. This facility cannot log unrecognized arguments,
30693 because the arguments are checked before the configuration file is read. The
30694 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
30695 between the caller and Exim.
30697 .cindex "log" "connection rejections"
30698 &%connection_reject%&: A log entry is written whenever an incoming SMTP
30699 connection is rejected, for whatever reason.
30701 .cindex "log" "delayed delivery"
30702 .cindex "delayed delivery" "logging"
30703 &%delay_delivery%&: A log entry is written whenever a delivery process is not
30704 started for an incoming message because the load is too high or too many
30705 messages were received on one connection. Logging does not occur if no delivery
30706 process is started because &%queue_only%& is set or &%-odq%& was used.
30708 .cindex "log" "delivery duration"
30709 &%deliver_time%&: For each delivery, the amount of real time it has taken to
30710 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
30712 .cindex "log" "message size on delivery"
30713 .cindex "size" "of message"
30714 &%delivery_size%&: For each delivery, the size of message delivered is added to
30715 the &"=>"& line, tagged with S=.
30717 .cindex "log" "dnslist defer"
30718 .cindex "DNS list" "logging defer"
30719 .cindex "black list (DNS)"
30720 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
30721 DNS black list suffers a temporary error.
30723 .cindex "log" "ETRN commands"
30724 .cindex "ETRN" "logging"
30725 &%etrn%&: Every legal ETRN command that is received is logged, before the ACL
30726 is run to determine whether or not it is actually accepted. An invalid ETRN
30727 command, or one received within a message transaction is not logged by this
30728 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
30730 .cindex "log" "host lookup failure"
30731 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
30732 any addresses, or when a lookup of an IP address fails to find a host name, a
30733 log line is written. This logging does not apply to direct DNS lookups when
30734 routing email addresses, but it does apply to &"byname"& lookups.
30736 .cindex "log" "ident timeout"
30737 .cindex "RFC 1413" "logging timeout"
30738 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
30739 client's ident port times out.
30741 .cindex "log" "incoming interface"
30742 .cindex "interface" "logging"
30743 &%incoming_interface%&: The interface on which a message was received is added
30744 to the &"<="& line as an IP address in square brackets, tagged by I= and
30745 followed by a colon and the port number. The local interface and port are also
30746 added to other SMTP log lines, for example &"SMTP connection from"&, and to
30749 .cindex "log" "incoming remote port"
30750 .cindex "port" "logging remote"
30751 .cindex "TCP/IP" "logging incoming remote port"
30752 .cindex "&$sender_fullhost$&"
30753 .cindex "&$sender_rcvhost$&"
30754 &%incoming_port%&: The remote port number from which a message was received is
30755 added to log entries and &'Received:'& header lines, following the IP address
30756 in square brackets, and separated from it by a colon. This is implemented by
30757 changing the value that is put in the &$sender_fullhost$& and
30758 &$sender_rcvhost$& variables. Recording the remote port number has become more
30759 important with the widening use of NAT (see RFC 2505).
30761 .cindex "log" "dropped connection"
30762 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
30763 connection is unexpectedly dropped.
30765 .cindex "log" "outgoing remote port"
30766 .cindex "port" "logging outgoint remote"
30767 .cindex "TCP/IP" "logging ougtoing remote port"
30768 &%outgoing_port%&: The remote port number is added to delivery log lines (those
30769 containing => tags) following the IP address. This option is not included in
30770 the default setting, because for most ordinary configurations, the remote port
30771 number is always 25 (the SMTP port).
30773 .cindex "log" "queue run"
30774 .cindex "queue runner" "logging"
30775 &%queue_run%&: The start and end of every queue run are logged.
30777 .cindex "log" "queue time"
30778 &%queue_time%&: The amount of time the message has been in the queue on the
30779 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
30780 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
30781 includes reception time as well as the delivery time for the current address.
30782 This means that it may be longer than the difference between the arrival and
30783 delivery log line times, because the arrival log line is not written until the
30784 message has been successfully received.
30786 &%queue_time_overall%&: The amount of time the message has been in the queue on
30787 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
30788 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
30789 message, so it includes reception time as well as the total delivery time.
30791 .cindex "log" "recipients"
30792 &%received_recipients%&: The recipients of a message are listed in the main log
30793 as soon as the message is received. The list appears at the end of the log line
30794 that is written when a message is received, preceded by the word &"for"&. The
30795 addresses are listed after they have been qualified, but before any rewriting
30797 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
30800 .cindex "log" "sender reception"
30801 &%received_sender%&: The unrewritten original sender of a message is added to
30802 the end of the log line that records the message's arrival, after the word
30803 &"from"& (before the recipients if &%received_recipients%& is also set).
30805 .cindex "log" "header lines for rejection"
30806 &%rejected_header%&: If a message's header has been received at the time a
30807 rejection is written to the reject log, the complete header is added to the
30808 log. Header logging can be turned off individually for messages that are
30809 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
30811 .cindex "log" "retry defer"
30812 &%retry_defer%&: A log line is written if a delivery is deferred because a
30813 retry time has not yet been reached. However, this &"retry time not reached"&
30814 message is always omitted from individual message logs after the first delivery
30817 .cindex "log" "return path"
30818 &%return_path_on_delivery%&: The return path that is being transmitted with
30819 the message is included in delivery and bounce lines, using the tag P=.
30820 This is omitted if no delivery actually happens, for example, if routing fails,
30821 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
30823 .cindex "log" "sender on delivery"
30824 &%sender_on_delivery%&: The message's sender address is added to every delivery
30825 and bounce line, tagged by F= (for &"from"&).
30826 This is the original sender that was received with the message; it is not
30827 necessarily the same as the outgoing return path.
30830 .cindex "log" "sender verify failure"
30831 &%sender_verify_failure%&: If this selector is unset, the separate log line
30832 that gives details of a sender verification failure is not written. Log lines
30833 for the rejection of SMTP commands contain just &"sender verify failed"&, so
30834 some detail is lost.
30837 .cindex "log" "size rejection"
30838 &%size_reject%&: A log line is written whenever a message is rejected because
30841 .cindex "log" "frozen messages; skipped"
30842 .cindex "frozen messages" "logging skipping"
30843 &%skip_delivery%&: A log line is written whenever a message is skipped during a
30844 queue run because it is frozen or because another process is already delivering
30846 .cindex "&""spool file is locked""&"
30847 The message that is written is &"spool file is locked"&.
30849 .cindex "log" "smtp confirmation"
30850 .cindex "SMTP" "logging confirmation"
30851 &%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for
30852 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
30853 A number of MTAs (including Exim) return an identifying string in this
30856 .cindex "log" "SMTP connections"
30857 .cindex "SMTP" "logging connections"
30858 &%smtp_connection%&: A log line is written whenever an SMTP connection is
30859 established or closed, unless the connection is from a host that matches
30860 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
30861 only when the closure is unexpected.) This applies to connections from local
30862 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
30863 dropped in the middle of a message, a log line is always written, whether or
30864 not this selector is set, but otherwise nothing is written at the start and end
30865 of connections unless this selector is enabled.
30867 For TCP/IP connections to an Exim daemon, the current number of connections is
30868 included in the log message for each new connection, but note that the count is
30869 reset if the daemon is restarted.
30870 Also, because connections are closed (and the closure is logged) in
30871 subprocesses, the count may not include connections that have been closed but
30872 whose termination the daemon has not yet noticed. Thus, while it is possible to
30873 match up the opening and closing of connections in the log, the value of the
30874 logged counts may not be entirely accurate.
30876 .cindex "log" "SMTP transaction; incomplete"
30877 .cindex "SMTP" "logging incomplete transactions"
30878 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
30879 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
30880 and the message sender plus any accepted recipients are included in the log
30881 line. This can provide evidence of dictionary attacks.
30883 .cindex "log" "SMTP protocol error"
30884 .cindex "SMTP" "logging protocol error"
30885 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
30886 encountered. Exim does not have perfect detection of all protocol errors
30887 because of transmission delays and the use of pipelining. If PIPELINING has
30888 been advertised to a client, an Exim server assumes that the client will use
30889 it, and therefore it does not count &"expected"& errors (for example, RCPT
30890 received after rejecting MAIL) as protocol errors.
30892 .cindex "SMTP" "logging syntax errors"
30893 .cindex "SMTP" "syntax errors; logging"
30894 .cindex "SMTP" "unknown command; logging"
30895 .cindex "log" "unknown SMTP command"
30896 .cindex "log" "SMTP syntax error"
30897 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
30898 encountered. An unrecognized command is treated as a syntax error. For an
30899 external connection, the host identity is given; for an internal connection
30900 using &%-bs%& the sender identification (normally the calling user) is given.
30902 .cindex "log" "subject"
30903 .cindex "subject" "logging"
30904 &%subject%&: The subject of the message is added to the arrival log line,
30905 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
30906 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
30907 specifies whether characters with values greater than 127 should be logged
30908 unchanged, or whether they should be rendered as escape sequences.
30910 .cindex "log" "certificate verification"
30911 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
30912 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
30913 verified, and &`CV=no`& if not.
30915 .cindex "log" "TLS cipher"
30916 .cindex "TLS" "logging cipher"
30917 &%tls_cipher%&: When a message is sent or received over an encrypted
30918 connection, the cipher suite used is added to the log line, preceded by X=.
30920 .cindex "log" "TLS peer DN"
30921 .cindex "TLS" "logging peer DN"
30922 &%tls_peerdn%&: When a message is sent or received over an encrypted
30923 connection, and a certificate is supplied by the remote host, the peer DN is
30924 added to the log line, preceded by DN=.
30926 .cindex "log" "DNS failure in list"
30927 &%unknown_in_list%&: This setting causes a log entry to be written when the
30928 result of a list match is failure because a DNS lookup failed.
30932 .section "Message log"
30933 .cindex "message" "log file for"
30934 .cindex "log" "message log; description of"
30935 .cindex "&_msglog_& directory"
30936 .cindex "&%preserve_message_logs%&"
30937 In addition to the general log files, Exim writes a log file for each message
30938 that it handles. The names of these per-message logs are the message ids, and
30939 they are kept in the &_msglog_& sub-directory of the spool directory. Each
30940 message log contains copies of the log lines that apply to the message. This
30941 makes it easier to inspect the status of an individual message without having
30942 to search the main log. A message log is deleted when processing of the message
30943 is complete, unless &%preserve_message_logs%& is set, but this should be used
30944 only with great care because they can fill up your disk very quickly.
30946 On a heavily loaded system, it may be desirable to disable the use of
30947 per-message logs, in order to reduce disk I/O. This can be done by setting the
30948 &%message_logs%& option false.
30952 . ////////////////////////////////////////////////////////////////////////////
30953 . ////////////////////////////////////////////////////////////////////////////
30955 .chapter "Exim utilities" "CHAPutils"
30956 .scindex IIDutils "utilities"
30957 A number of utility scripts and programs are supplied with Exim and are
30958 described in this chapter. There is also the Exim Monitor, which is covered in
30959 the next chapter. The utilities described here are:
30961 .itable none 0 0 4 2* left 8* left 30* left 40* left
30962 .row "" &<<SECTfinoutwha>>& &'exiwhat'& &&&
30963 "list what Exim processes are doing"
30964 .row "" &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
30965 .row "" &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
30966 .row "" &<<SECTextspeinf>>& &'exigrep'& "search the main log"
30967 .row "" &<<SECTexipick>>& &'exipick'& "select messages on &&&
30969 .row "" &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
30970 .row "" &<<SECTmailstat>>& &'eximstats'& &&&
30971 "extract statistics from the log"
30972 .row "" &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
30973 "check address acceptance from given IP"
30974 .row "" &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
30975 .row "" &<<SECTfinindret>>& &'exinext'& "extract retry information"
30976 .row "" &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
30977 .row "" &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
30978 .row "" &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
30979 .row "" &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
30982 Another utility that might be of use to sites with many MTAs is Tom Kistner's
30983 &'exilog'&. It provides log visualizations across multiple Exim servers. See
30984 &url(http://duncanthrax.net/exilog/) for details.
30989 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
30990 .cindex "&'exiwhat'&"
30991 .cindex "process" "querying"
30993 On operating systems that can restart a system call after receiving a signal
30994 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
30995 a line describing what it is doing to the file &_exim-process.info_& in the
30996 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
30997 processes it can find, having first emptied the file. It then waits for one
30998 second to allow the Exim processes to react before displaying the results. In
30999 order to run &'exiwhat'& successfully you have to have sufficient privilege to
31000 send the signal to the Exim processes, so it is normally run as root.
31002 &*Warning*&: This is not an efficient process. It is intended for occasional
31003 use by system administrators. It is not sensible, for example, to set up a
31004 script that sends SIGUSR1 signals to Exim processes at short intervals.
31007 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
31008 varies in different operating systems. Not only are different options used,
31009 but the format of the output is different. For this reason, there are some
31010 system configuration options that configure exactly how &'exiwhat'& works. If
31011 it doesn't seem to be working for you, check the following compile-time
31014 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
31015 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
31016 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
31017 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
31019 An example of typical output from &'exiwhat'& is
31021 164 daemon: -q1h, listening on port 25
31022 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
31023 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
31024 [10.19.42.42] (editor@ref.example)
31025 10592 handling incoming call from [192.168.243.242]
31026 10628 accepting a local non-SMTP message
31028 The first number in the output line is the process number. The third line has
31029 been split here, in order to fit it on the page.
31033 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
31034 .cindex "&'exiqgrep'&"
31035 .cindex "queue" "grepping"
31036 This utility is a Perl script contributed by Matt Hubbard. It runs
31040 to obtain a queue listing with undelivered recipients only, and then greps the
31041 output to select messages that match given criteria. The following selection
31042 options are available:
31045 .vitem &*-f*&&~<&'regex'&>
31046 Match the sender address. The field that is tested is enclosed in angle
31047 brackets, so you can test for bounce messages with
31051 .vitem &*-r*&&~<&'regex'&>
31052 Match a recipient address. The field that is tested is not enclosed in angle
31055 .vitem &*-s*&&~<&'regex'&>
31056 Match against the size field.
31058 .vitem &*-y*&&~<&'seconds'&>
31059 Match messages that are younger than the given time.
31061 .vitem &*-o*&&~<&'seconds'&>
31062 Match messages that are older than the given time.
31065 Match only frozen messages.
31068 Match only non-frozen messages.
31071 The following options control the format of the output:
31075 Display only the count of matching messages.
31078 Long format &-- display the full message information as output by Exim. This is
31082 Display message ids only.
31085 Brief format &-- one line per message.
31088 Display messages in reverse order.
31091 There is one more option, &%-h%&, which outputs a list of options.
31095 .section "Summarising the queue (exiqsumm)" "SECTsumtheque"
31096 .cindex "&'exiqsumm'&"
31097 .cindex "queue" "summary"
31098 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
31099 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
31100 running a command such as
31102 exim -bp | exiqsumm
31104 The output consists of one line for each domain that has messages waiting for
31105 it, as in the following example:
31107 3 2322 74m 66m msn.com.example
31109 Each line lists the number of
31110 pending deliveries for a domain, their total volume, and the length of time
31111 that the oldest and the newest messages have been waiting. Note that the number
31112 of pending deliveries is greater than the number of messages when messages
31113 have more than one recipient.
31115 A summary line is output at the end. By default the output is sorted on the
31116 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
31117 the output to be sorted by oldest message and by count of messages,
31120 The output of &'exim -bp'& contains the original addresses in the message, so
31121 this also applies to the output from &'exiqsumm'&. No domains from addresses
31122 generated by aliasing or forwarding are included (unless the &%one_time%&
31123 option of the &(redirect)& router has been used to convert them into &"top
31124 level"& addresses).
31129 .section "Extracting specific information from the log (exigrep)" &&&
31131 .cindex "&'exigrep'&"
31132 .cindex "log" "extracts; grepping for"
31133 The &'exigrep'& utility is a Perl script that searches one or more main log
31134 files for entries that match a given pattern. When it finds a match, it
31135 extracts all the log entries for the relevant message, not just those that
31136 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
31137 given message, or all mail for a given user, or for a given host, for example.
31138 The input files can be in Exim log format or syslog format.
31140 If a matching log line is not associated with a specific message, it is always
31141 included in &'exigrep'&'s output. The usage is:
31143 &`exigrep [-l] [-t<`&&'n'&&`>] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
31145 The &%-t%& argument specifies a number of seconds. It adds an additional
31146 condition for message selection. Messages that are complete are shown only if
31147 they spent more than <&'n'&> seconds on the queue.
31149 The &%-l%& flag means &"literal"&, that is, treat all characters in the
31150 pattern as standing for themselves. Otherwise the pattern must be a Perl
31151 regular expression. The pattern match is case-insensitive. If no file names are
31152 given on the command line, the standard input is read.
31154 If the location of a &'zcat'& command is known from the definition of
31155 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
31156 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
31159 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
31160 .cindex "&'exipick'&"
31161 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
31162 lists messages from the queue according to a variety of criteria. For details,
31169 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
31171 .cindex "log" "cycling local files"
31172 .cindex "cycling logs"
31173 .cindex "&'exicyclog'&"
31174 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
31175 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
31176 you are using log files with datestamps in their names (see section
31177 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
31178 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
31179 There are two command line options for &'exicyclog'&:
31181 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
31182 default that is set when Exim is built. The default default is 10.
31184 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
31185 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
31186 overriding the script's default, which is to find the setting from Exim's
31190 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
31191 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
31192 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
31193 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
31194 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
31195 logs are handled similarly.
31198 If the limit is greater than 99, the script uses 3-digit numbers such as
31199 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
31200 to one that is greater, or &'vice versa'&, you will have to fix the names of
31201 any existing log files.
31203 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
31204 the end are deleted. All files with numbers greater than 01 are compressed,
31205 using a compression command which is configured by the COMPRESS_COMMAND
31206 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
31207 root &%crontab%& entry of the form
31209 1 0 * * * su exim -c /usr/exim/bin/exicyclog
31211 assuming you have used the name &"exim"& for the Exim user. You can run
31212 &'exicyclog'& as root if you wish, but there is no need.
31216 .section "Mail statistics (eximstats)" "SECTmailstat"
31217 .cindex "statistics"
31218 .cindex "&'eximstats'&"
31219 A Perl script called &'eximstats'& is provided for extracting statistical
31220 information from log files. The output is either plain text, or HTML.
31221 Exim log files are also suported by the &'Lire'& system produced by the
31222 LogReport Foundation &url(http://www.logreport.org).
31224 The &'eximstats'& script has been hacked about quite a bit over time. The
31225 latest version is the result of some extensive revision by Steve Campbell. A
31226 lot of information is given by default, but there are options for suppressing
31227 various parts of it. Following any options, the arguments to the script are a
31228 list of files, which should be main log files. For example:
31230 eximstats -nr /var/spool/exim/log/mainlog.01
31232 By default, &'eximstats'& extracts information about the number and volume of
31233 messages received from or delivered to various hosts. The information is sorted
31234 both by message count and by volume, and the top fifty hosts in each category
31235 are listed on the standard output. Similar information, based on email
31236 addresses or domains instead of hosts can be requested by means of various
31237 options. For messages delivered and received locally, similar statistics are
31238 also produced per user.
31240 The output also includes total counts and statistics about delivery errors, and
31241 histograms showing the number of messages received and deliveries made in each
31242 hour of the day. A delivery with more than one address in its envelope (for
31243 example, an SMTP transaction with more than one RCPT command) is counted
31244 as a single delivery by &'eximstats'&.
31246 Though normally more deliveries than receipts are reported (as messages may
31247 have multiple recipients), it is possible for &'eximstats'& to report more
31248 messages received than delivered, even though the queue is empty at the start
31249 and end of the period in question. If an incoming message contains no valid
31250 recipients, no deliveries are recorded for it. A bounce message is handled as
31251 an entirely separate message.
31253 &'eximstats'& always outputs a grand total summary giving the volume and number
31254 of messages received and deliveries made, and the number of hosts involved in
31255 each case. It also outputs the number of messages that were delayed (that is,
31256 not completely delivered at the first attempt), and the number that had at
31257 least one address that failed.
31259 The remainder of the output is in sections that can be independently disabled
31260 or modified by various options. It consists of a summary of deliveries by
31261 transport, histograms of messages received and delivered per time interval
31262 (default per hour), information about the time messages spent on the queue,
31263 a list of relayed messages, lists of the top fifty sending hosts, local
31264 senders, destination hosts, and destination local users by count and by volume,
31265 and a list of delivery errors that occurred.
31267 The relay information lists messages that were actually relayed, that is, they
31268 came from a remote host and were directly delivered to some other remote host,
31269 without being processed (for example, for aliasing or forwarding) locally.
31271 There are quite a few options for &'eximstats'& to control exactly what it
31272 outputs. These are documented in the Perl script itself, and can be extracted
31273 by running the command &(perldoc)& on the script. For example:
31275 perldoc /usr/exim/bin/eximstats
31278 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
31279 .cindex "&'exim_checkaccess'&"
31280 .cindex "policy control" "checking access"
31281 .cindex "checking access"
31282 The &%-bh%& command line argument allows you to run a fake SMTP session with
31283 debugging output, in order to check what Exim is doing when it is applying
31284 policy controls to incoming SMTP mail. However, not everybody is sufficiently
31285 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
31286 sometimes you just want to answer the question &"Does this address have
31287 access?"& without bothering with any further details.
31289 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
31290 two arguments, an IP address and an email address:
31292 exim_checkaccess 10.9.8.7 A.User@a.domain.example
31294 The utility runs a call to Exim with the &%-bh%& option, to test whether the
31295 given email address would be accepted in a RCPT command in a TCP/IP
31296 connection from the host with the given IP address. The output of the utility
31297 is either the word &"accepted"&, or the SMTP error response, for example:
31300 550 Relay not permitted
31302 When running this test, the utility uses &`<>`& as the envelope sender address
31303 for the MAIL command, but you can change this by providing additional
31304 options. These are passed directly to the Exim command. For example, to specify
31305 that the test is to be run with the sender address &'himself@there.example'&
31308 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
31309 -f himself@there.example
31311 Note that these additional Exim command line items must be given after the two
31312 mandatory arguments.
31314 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
31315 while running its checks. You can run checks that include callouts by using
31316 &%-bhc%&, but this is not yet available in a &"packaged"& form.
31320 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
31321 .cindex "DBM" "building dbm files"
31322 .cindex "building DBM files"
31323 .cindex "&'exim_dbmbuild'&"
31324 .cindex "lower casing"
31325 .cindex "binary zero" "in lookup key"
31326 The &'exim_dbmbuild'& program reads an input file containing keys and data in
31327 the format used by the &(lsearch)& lookup (see section
31328 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
31329 names as keys and the remainder of the information as data. The lower-casing
31330 can be prevented by calling the program with the &%-nolc%& option.
31332 A terminating zero is included as part of the key string. This is expected by
31333 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
31334 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
31335 strings or the data strings. The &(dbmnz)& lookup type can be used with such
31338 The program requires two arguments: the name of the input file (which can be a
31339 single hyphen to indicate the standard input), and the name of the output file.
31340 It creates the output under a temporary name, and then renames it if all went
31344 If the native DB interface is in use (USE_DB is set in a compile-time
31345 configuration file &-- this is common in free versions of Unix) the two file
31346 names must be different, because in this mode the Berkeley DB functions create
31347 a single output file using exactly the name given. For example,
31349 exim_dbmbuild /etc/aliases /etc/aliases.db
31351 reads the system alias file and creates a DBM version of it in
31352 &_/etc/aliases.db_&.
31354 In systems that use the &'ndbm'& routines (mostly proprietary versions of
31355 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
31356 environment, the suffixes are added to the second argument of
31357 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
31358 when the Berkeley functions are used in compatibility mode (though this is not
31359 recommended), because in that case it adds a &_.db_& suffix to the file name.
31361 If a duplicate key is encountered, the program outputs a warning, and when it
31362 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
31363 option is used. By default, only the first of a set of duplicates is used &--
31364 this makes it compatible with &(lsearch)& lookups. There is an option
31365 &%-lastdup%& which causes it to use the data for the last duplicate instead.
31366 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
31367 &%stderr%&. For other errors, where it doesn't actually make a new file, the
31373 .section "Finding individual retry times (exinext)" "SECTfinindret"
31374 .cindex "retry" "times"
31375 .cindex "&'exinext'&"
31376 A utility called &'exinext'& (mostly a Perl script) provides the ability to
31377 fish specific information out of the retry database. Given a mail domain (or a
31378 complete address), it looks up the hosts for that domain, and outputs any retry
31379 information for the hosts or for the domain. At present, the retry information
31380 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
31381 output. For example:
31383 $ exinext piglet@milne.fict.example
31384 kanga.milne.example:192.168.8.1 error 146: Connection refused
31385 first failed: 21-Feb-1996 14:57:34
31386 last tried: 21-Feb-1996 14:57:34
31387 next try at: 21-Feb-1996 15:02:34
31388 roo.milne.example:192.168.8.3 error 146: Connection refused
31389 first failed: 20-Jan-1996 13:12:08
31390 last tried: 21-Feb-1996 11:42:03
31391 next try at: 21-Feb-1996 19:42:03
31392 past final cutoff time
31394 You can also give &'exinext'& a local part, without a domain, and it
31395 will give any retry information for that local part in your default domain.
31396 A message id can be used to obtain retry information pertaining to a specific
31397 message. This exists only when an attempt to deliver a message to a remote host
31398 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
31399 &'exinext'& is not particularly efficient, but then it is not expected to be
31402 The &'exinext'& utility calls Exim to find out information such as the location
31403 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
31404 passed on to the &'exim'& commands. The first specifies an alternate Exim
31405 configuration file, and the second sets macros for use within the configuration
31406 file. These features are mainly to help in testing, but might also be useful in
31407 environments where more than one configuration file is in use.
31411 .section "Hints database maintenance" "SECThindatmai"
31412 .cindex "hints database" "maintenance"
31413 .cindex "maintaining Exim's hints database"
31414 Three utility programs are provided for maintaining the DBM files that Exim
31415 uses to contain its delivery hint information. Each program requires two
31416 arguments. The first specifies the name of Exim's spool directory, and the
31417 second is the name of the database it is to operate on. These are as follows:
31420 &'retry'&: the database of retry information
31422 &'wait-'&<&'transport name'&>: databases of information about messages waiting
31425 &'callout'&: the callout cache
31427 &'ratelimit'&: the data for implementing the ratelimit ACL condition
31429 &'misc'&: other hints data
31432 The &'misc'& database is used for
31435 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
31437 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
31438 &(smtp)& transport)
31443 .section "exim_dumpdb"
31444 .cindex "&'exim_dumpdb'&"
31445 The entire contents of a database are written to the standard output by the
31446 &'exim_dumpdb'& program, which has no options or arguments other than the
31447 spool and database names. For example, to dump the retry database:
31449 exim_dumpdb /var/spool/exim retry
31451 Two lines of output are produced for each entry:
31453 T:mail.ref.example:192.168.242.242 146 77 Connection refused
31454 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
31456 The first item on the first line is the key of the record. It starts with one
31457 of the letters R, or T, depending on whether it refers to a routing or
31458 transport retry. For a local delivery, the next part is the local address; for
31459 a remote delivery it is the name of the remote host, followed by its failing IP
31460 address (unless &%no_retry_include_ip_address%& is set on the &(smtp)&
31461 transport). If the remote port is not the standard one (port 25), it is added
31462 to the IP address. Then there follows an error code, an additional error code,
31463 and a textual description of the error.
31465 The three times on the second line are the time of first failure, the time of
31466 the last delivery attempt, and the computed time for the next attempt. The line
31467 ends with an asterisk if the cutoff time for the last retry rule has been
31470 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
31471 consists of a host name followed by a list of ids for messages that are or were
31472 waiting to be delivered to that host. If there are a very large number for any
31473 one host, continuation records, with a sequence number added to the host name,
31474 may be seen. The data in these records is often out of date, because a message
31475 may be routed to several alternative hosts, and Exim makes no effort to keep
31480 .section "exim_tidydb"
31481 .cindex "&'exim_tidydb'&"
31482 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
31483 database. If run with no options, it removes all records that are more than 30
31484 days old. The age is calculated from the date and time that the record was last
31485 updated. Note that, in the case of the retry database, it is &'not'& the time
31486 since the first delivery failure. Information about a host that has been down
31487 for more than 30 days will remain in the database, provided that the record is
31488 updated sufficiently often.
31490 The cutoff date can be altered by means of the &%-t%& option, which must be
31491 followed by a time. For example, to remove all records older than a week from
31492 the retry database:
31494 exim_tidydb -t 7d /var/spool/exim retry
31496 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
31497 message ids. In the former these appear as data in records keyed by host &--
31498 they were messages that were waiting for that host &-- and in the latter they
31499 are the keys for retry information for messages that have suffered certain
31500 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
31501 message ids in database records are those of messages that are still on the
31502 queue. Message ids for messages that no longer exist are removed from
31503 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
31504 For the &'retry'& database, records whose keys are non-existent message ids are
31505 removed. The &'exim_tidydb'& utility outputs comments on the standard output
31506 whenever it removes information from the database.
31508 Certain records are automatically removed by Exim when they are no longer
31509 needed, but others are not. For example, if all the MX hosts for a domain are
31510 down, a retry record is created for each one. If the primary MX host comes back
31511 first, its record is removed when Exim successfully delivers to it, but the
31512 records for the others remain because Exim has not tried to use those hosts.
31514 It is important, therefore, to run &'exim_tidydb'& periodically on all the
31515 hints databases. You should do this at a quiet time of day, because it requires
31516 a database to be locked (and therefore inaccessible to Exim) while it does its
31517 work. Removing records from a DBM file does not normally make the file smaller,
31518 but all the common DBM libraries are able to re-use the space that is released.
31519 After an initial phase of increasing in size, the databases normally reach a
31520 point at which they no longer get any bigger, as long as they are regularly
31523 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
31524 databases is likely to keep on increasing.
31529 .section "exim_fixdb"
31530 .cindex "&'exim_fixdb'&"
31531 The &'exim_fixdb'& program is a utility for interactively modifying databases.
31532 Its main use is for testing Exim, but it might also be occasionally useful for
31533 getting round problems in a live system. It has no options, and its interface
31534 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
31535 key of a database record can then be entered, and the data for that record is
31538 If &"d"& is typed at the next prompt, the entire record is deleted. For all
31539 except the &'retry'& database, that is the only operation that can be carried
31540 out. For the &'retry'& database, each field is output preceded by a number, and
31541 data for individual fields can be changed by typing the field number followed
31542 by new data, for example:
31546 resets the time of the next delivery attempt. Time values are given as a
31547 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
31548 used as optional separators.
31553 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
31554 .cindex "mailbox" "maintenance"
31555 .cindex "&'exim_lock'&"
31556 .cindex "locking mailboxes"
31557 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
31558 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
31559 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
31560 a user agent while investigating a problem. The utility requires the name of
31561 the file as its first argument. If the locking is successful, the second
31562 argument is run as a command (using C's &[system()]& function); if there is no
31563 second argument, the value of the SHELL environment variable is used; if this
31564 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
31565 is unlocked and the utility ends. The following options are available:
31569 Use &[fcntl()]& locking on the open mailbox.
31572 Use &[flock()]& locking on the open mailbox, provided the operating system
31575 .vitem &%-interval%&
31576 This must be followed by a number, which is a number of seconds; it sets the
31577 interval to sleep between retries (default 3).
31579 .vitem &%-lockfile%&
31580 Create a lock file before opening the mailbox.
31583 Lock the mailbox using MBX rules.
31586 Suppress verification output.
31588 .vitem &%-retries%&
31589 This must be followed by a number; it sets the number of times to try to get
31590 the lock (default 10).
31592 .vitem &%-restore_time%&
31593 This option causes &%exim_lock%& to restore the modified and read times to the
31594 locked file before exiting. This allows you to access a locked mailbox (for
31595 example, to take a backup copy) without disturbing the times that the user
31598 .vitem &%-timeout%&
31599 This must be followed by a number, which is a number of seconds; it sets a
31600 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
31601 default), a non-blocking call is used.
31604 Generate verbose output.
31607 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
31608 default is to create a lock file and also to use &[fcntl()]& locking on the
31609 mailbox, which is the same as Exim's default. The use of &%-flock%& or
31610 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
31611 requires that the directory containing the file be writeable. Locking by lock
31612 file does not last for ever; Exim assumes that a lock file is expired if it is
31613 more than 30 minutes old.
31615 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
31616 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
31617 to be taken out on the open mailbox, and an exclusive lock on the file
31618 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
31619 number of the mailbox file. When the locking is released, if an exclusive lock
31620 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
31622 The default output contains verification of the locking that takes place. The
31623 &%-v%& option causes some additional information to be given. The &%-q%& option
31624 suppresses all output except error messages.
31628 exim_lock /var/spool/mail/spqr
31630 runs an interactive shell while the file is locked, whereas
31632 &`exim_lock -q /var/spool/mail/spqr <<End`&
31633 <&'some commands'&>
31636 runs a specific non-interactive sequence of commands while the file is locked,
31637 suppressing all verification output. A single command can be run by a command
31640 exim_lock -q /var/spool/mail/spqr \
31641 "cp /var/spool/mail/spqr /some/where"
31643 Note that if a command is supplied, it must be entirely contained within the
31644 second argument &-- hence the quotes.
31648 . ////////////////////////////////////////////////////////////////////////////
31649 . ////////////////////////////////////////////////////////////////////////////
31651 .chapter "The Exim monitor" "CHAPeximon"
31652 .scindex IIDeximon "Exim monitor" "description"
31653 .cindex "X-windows"
31654 .cindex "&'eximon'&"
31655 .cindex "Local/eximon.conf"
31656 .cindex "_exim_monitor/EDITME_"
31657 The Exim monitor is an application which displays in an X window information
31658 about the state of Exim's queue and what Exim is doing. An admin user can
31659 perform certain operations on messages from this GUI interface; however all
31660 such facilities are also available from the command line, and indeed, the
31661 monitor itself makes use of the command line to perform any actions requested.
31665 .section "Running the monitor"
31666 The monitor is started by running the script called &'eximon'&. This is a shell
31667 script that sets up a number of environment variables, and then runs the
31668 binary called &_eximon.bin_&. The default appearance of the monitor window can
31669 be changed by editing the &_Local/eximon.conf_& file created by editing
31670 &_exim_monitor/EDITME_&. Comments in that file describe what the various
31671 parameters are for.
31673 The parameters that get built into the &'eximon'& script can be overridden for
31674 a particular invocation by setting up environment variables of the same names,
31675 preceded by &`EXIMON_`&. For example, a shell command such as
31677 EXIMON_LOG_DEPTH=400 eximon
31679 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
31680 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
31681 overrides the Exim log file configuration. This makes it possible to have
31682 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
31683 syslog messages are routed to a file on the local host.
31685 X resources can be used to change the appearance of the window in the normal
31686 way. For example, a resource setting of the form
31688 Eximon*background: gray94
31690 changes the colour of the background to light grey rather than white. The
31691 stripcharts are drawn with both the data lines and the reference lines in
31692 black. This means that the reference lines are not visible when on top of the
31693 data. However, their colour can be changed by setting a resource called
31694 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
31695 For example, if your X server is running Unix, you could set up lighter
31696 reference lines in the stripcharts by obeying
31699 Eximon*highlight: gray
31702 .cindex "admin user"
31703 In order to see the contents of messages on the queue, and to operate on them,
31704 &'eximon'& must either be run as root or by an admin user.
31706 The monitor's window is divided into three parts. The first contains one or
31707 more stripcharts and two action buttons, the second contains a &"tail"& of the
31708 main log file, and the third is a display of the queue of messages awaiting
31709 delivery, with two more action buttons. The following sections describe these
31710 different parts of the display.
31715 .section "The stripcharts"
31716 .cindex "stripchart"
31717 The first stripchart is always a count of messages on the queue. Its name can
31718 be configured by setting QUEUE_STRIPCHART_NAME in the
31719 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
31720 configuration script by regular expression matches on log file entries, making
31721 it possible to display, for example, counts of messages delivered to certain
31722 hosts or using certain transports. The supplied defaults display counts of
31723 received and delivered messages, and of local and SMTP deliveries. The default
31724 period between stripchart updates is one minute; this can be adjusted by a
31725 parameter in the &_Local/eximon.conf_& file.
31727 The stripchart displays rescale themselves automatically as the value they are
31728 displaying changes. There are always 10 horizontal lines in each chart; the
31729 title string indicates the value of each division when it is greater than one.
31730 For example, &"x2"& means that each division represents a value of 2.
31732 It is also possible to have a stripchart which shows the percentage fullness of
31733 a particular disk partition, which is useful when local deliveries are confined
31734 to a single partition.
31736 .cindex "&%statvfs%& function"
31737 This relies on the availability of the &[statvfs()]& function or equivalent in
31738 the operating system. Most, but not all versions of Unix that support Exim have
31739 this. For this particular stripchart, the top of the chart always represents
31740 100%, and the scale is given as &"x10%"&. This chart is configured by setting
31741 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
31742 &_Local/eximon.conf_& file.
31747 .section "Main action buttons"
31748 .cindex "size" "of monitor window"
31749 .cindex "Exim monitor" "window size"
31750 .cindex "window size"
31751 Below the stripcharts there is an action button for quitting the monitor. Next
31752 to this is another button marked &"Size"&. They are placed here so that
31753 shrinking the window to its default minimum size leaves just the queue count
31754 stripchart and these two buttons visible. Pressing the &"Size"& button causes
31755 the window to expand to its maximum size, unless it is already at the maximum,
31756 in which case it is reduced to its minimum.
31758 When expanding to the maximum, if the window cannot be fully seen where it
31759 currently is, it is moved back to where it was the last time it was at full
31760 size. When it is expanding from its minimum size, the old position is
31761 remembered, and next time it is reduced to the minimum it is moved back there.
31763 The idea is that you can keep a reduced window just showing one or two
31764 stripcharts at a convenient place on your screen, easily expand it to show
31765 the full window when required, and just as easily put it back to what it was.
31766 The idea is copied from what the &'twm'& window manager does for its
31767 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
31768 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
31770 Normally, the monitor starts up with the window at its full size, but it can be
31771 built so that it starts up with the window at its smallest size, by setting
31772 START_SMALL=yes in &_Local/eximon.conf_&.
31776 .section "The log display"
31777 .cindex "log" "tail of; in monitor"
31778 The second section of the window is an area in which a display of the tail of
31779 the main log is maintained.
31780 To save space on the screen, the timestamp on each log line is shortened by
31781 removing the date and, if &%log_timezone%& is set, the timezone.
31782 The log tail is not available when the only destination for logging data is
31783 syslog, unless the syslog lines are routed to a local file whose name is passed
31784 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
31786 The log sub-window has a scroll bar at its lefthand side which can be used to
31787 move back to look at earlier text, and the up and down arrow keys also have a
31788 scrolling effect. The amount of log that is kept depends on the setting of
31789 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
31790 to use. When this is full, the earlier 50% of data is discarded &-- this is
31791 much more efficient than throwing it away line by line. The sub-window also has
31792 a horizontal scroll bar for accessing the ends of long log lines. This is the
31793 only means of horizontal scrolling; the right and left arrow keys are not
31794 available. Text can be cut from this part of the window using the mouse in the
31795 normal way. The size of this subwindow is controlled by parameters in the
31796 configuration file &_Local/eximon.conf_&.
31798 Searches of the text in the log window can be carried out by means of the ^R
31799 and ^S keystrokes, which default to a reverse and a forward search,
31800 respectively. The search covers only the text that is displayed in the window.
31801 It cannot go further back up the log.
31803 The point from which the search starts is indicated by a caret marker. This is
31804 normally at the end of the text in the window, but can be positioned explicitly
31805 by pointing and clicking with the left mouse button, and is moved automatically
31806 by a successful search. If new text arrives in the window when it is scrolled
31807 back, the caret remains where it is, but if the window is not scrolled back,
31808 the caret is moved to the end of the new text.
31810 Pressing ^R or ^S pops up a window into which the search text can be typed.
31811 There are buttons for selecting forward or reverse searching, for carrying out
31812 the search, and for cancelling. If the &"Search"& button is pressed, the search
31813 happens and the window remains so that further searches can be done. If the
31814 &"Return"& key is pressed, a single search is done and the window is closed. If
31815 ^C is typed the search is cancelled.
31817 The searching facility is implemented using the facilities of the Athena text
31818 widget. By default this pops up a window containing both &"search"& and
31819 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
31820 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
31821 However, the linkers in BSDI and HP-UX seem unable to handle an externally
31822 provided version of &%TextPop%& when the remaining parts of the text widget
31823 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
31824 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
31825 on these systems, at the expense of having unwanted items in the search popup
31830 .section "The queue display"
31831 .cindex "queue" "display in monitor"
31832 The bottom section of the monitor window contains a list of all messages that
31833 are on the queue, which includes those currently being received or delivered,
31834 as well as those awaiting delivery. The size of this subwindow is controlled by
31835 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
31836 at which it is updated is controlled by another parameter in the same file &--
31837 the default is 5 minutes, since queue scans can be quite expensive. However,
31838 there is an &"Update"& action button just above the display which can be used
31839 to force an update of the queue display at any time.
31841 When a host is down for some time, a lot of pending mail can build up for it,
31842 and this can make it hard to deal with other messages on the queue. To help
31843 with this situation there is a button next to &"Update"& called &"Hide"&. If
31844 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
31845 type anything in here and press &"Return"&, the text is added to a chain of
31846 such texts, and if every undelivered address in a message matches at least one
31847 of the texts, the message is not displayed.
31849 If there is an address that does not match any of the texts, all the addresses
31850 are displayed as normal. The matching happens on the ends of addresses so, for
31851 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
31852 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
31853 has been set up, a button called &"Unhide"& is displayed. If pressed, it
31854 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
31855 a hide request is automatically cancelled after one hour.
31857 While the dialogue box is displayed, you can't press any buttons or do anything
31858 else to the monitor window. For this reason, if you want to cut text from the
31859 queue display to use in the dialogue box, you have to do the cutting before
31860 pressing the &"Hide"& button.
31862 The queue display contains, for each unhidden queued message, the length of
31863 time it has been on the queue, the size of the message, the message id, the
31864 message sender, and the first undelivered recipient, all on one line. If it is
31865 a bounce message, the sender is shown as &"<>"&. If there is more than one
31866 recipient to which the message has not yet been delivered, subsequent ones are
31867 listed on additional lines, up to a maximum configured number, following which
31868 an ellipsis is displayed. Recipients that have already received the message are
31871 .cindex "frozen messages" "display"
31872 If a message is frozen, an asterisk is displayed at the left-hand side.
31874 The queue display has a vertical scroll bar, and can also be scrolled by means
31875 of the arrow keys. Text can be cut from it using the mouse in the normal way.
31876 The text searching facilities, as described above for the log window, are also
31877 available, but the caret is always moved to the end of the text when the queue
31878 display is updated.
31882 .section "The queue menu"
31883 .cindex "queue" "menu in monitor"
31884 If the &%shift%& key is held down and the left button is clicked when the mouse
31885 pointer is over the text for any message, an action menu pops up, and the first
31886 line of the queue display for the message is highlighted. This does not affect
31889 If you want to use some other event for popping up the menu, you can set the
31890 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
31891 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
31892 value set in this parameter is a standard X event description. For example, to
31893 run eximon using &%ctrl%& rather than &%shift%& you could use
31895 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
31897 The title of the menu is the message id, and it contains entries which act as
31901 &'message log'&: The contents of the message log for the message are displayed
31902 in a new text window.
31904 &'headers'&: Information from the spool file that contains the envelope
31905 information and headers is displayed in a new text window. See chapter
31906 &<<CHAPspool>>& for a description of the format of spool files.
31908 &'body'&: The contents of the spool file containing the body of the message are
31909 displayed in a new text window. There is a default limit of 20,000 bytes to the
31910 amount of data displayed. This can be changed by setting the BODY_MAX
31911 option at compile time, or the EXIMON_BODY_MAX option at run time.
31913 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
31914 delivery of the message. This causes an automatic thaw if the message is
31915 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
31916 a new text window. The delivery is run in a separate process, to avoid holding
31917 up the monitor while the delivery proceeds.
31919 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
31920 that the message be frozen.
31922 .cindex "thawing messages"
31923 .cindex "unfreezing messages"
31924 .cindex "frozen messages" "thawing"
31925 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
31926 that the message be thawed.
31928 .cindex "delivery" "forcing failure"
31929 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
31930 that Exim gives up trying to deliver the message. A bounce message is generated
31931 for any remaining undelivered addresses.
31933 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
31934 that the message be deleted from the system without generating a bounce
31937 &'add recipient'&: A dialog box is displayed into which a recipient address can
31938 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
31939 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
31940 Otherwise it must be entered as a fully qualified address. Pressing RETURN
31941 causes a call to Exim to be made using the &%-Mar%& option to request that an
31942 additional recipient be added to the message, unless the entry box is empty, in
31943 which case no action is taken.
31945 &'mark delivered'&: A dialog box is displayed into which a recipient address
31946 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
31947 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
31948 Otherwise it must be entered as a fully qualified address. Pressing RETURN
31949 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
31950 recipient address as already delivered, unless the entry box is empty, in which
31951 case no action is taken.
31953 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
31954 mark all recipient addresses as already delivered.
31956 &'edit sender'&: A dialog box is displayed initialized with the current
31957 sender's address. Pressing RETURN causes a call to Exim to be made using the
31958 &%-Mes%& option to replace the sender address, unless the entry box is empty,
31959 in which case no action is taken. If you want to set an empty sender (as in
31960 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
31961 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
31962 the address is qualified with that domain.
31965 When a delivery is forced, a window showing the &%-v%& output is displayed. In
31966 other cases when a call to Exim is made, if there is any output from Exim (in
31967 particular, if the command fails) a window containing the command and the
31968 output is displayed. Otherwise, the results of the action are normally apparent
31969 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
31970 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
31971 if no output is generated.
31973 The queue display is automatically updated for actions such as freezing and
31974 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
31975 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
31976 force an update of the display after one of these actions.
31978 In any text window that is displayed as result of a menu action, the normal
31979 cut-and-paste facility is available, and searching can be carried out using ^R
31980 and ^S, as described above for the log tail window.
31987 . ////////////////////////////////////////////////////////////////////////////
31988 . ////////////////////////////////////////////////////////////////////////////
31990 .chapter "Security considerations" "CHAPsecurity"
31991 .scindex IIDsecurcon "security" "discussion of"
31992 This chapter discusses a number of issues concerned with security, some of
31993 which are also covered in other parts of this manual.
31995 For reasons that this author does not understand, some people have promoted
31996 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
31997 existence of this chapter in the documentation. However, the intent of the
31998 chapter is simply to describe the way Exim works in relation to certain
31999 security concerns, not to make any specific claims about the effectiveness of
32000 its security as compared with other MTAs.
32002 What follows is a description of the way Exim is supposed to be. Best efforts
32003 have been made to try to ensure that the code agrees with the theory, but an
32004 absence of bugs can never be guaranteed. Any that are reported will get fixed
32005 as soon as possible.
32008 .section "Building a more &""hardened""& Exim"
32009 .cindex "security" "build-time features"
32010 There are a number of build-time options that can be set in &_Local/Makefile_&
32011 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
32012 Exim administrator who does not have the root password, or by someone who has
32013 penetrated the Exim (but not the root) account. These options are as follows:
32016 ALT_CONFIG_PREFIX can be set to a string that is required to match the
32017 start of any file names used with the &%-C%& option. When it is set, these file
32018 names are also not allowed to contain the sequence &"/../"&. (However, if the
32019 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
32020 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
32021 default setting for &%ALT_CONFIG_PREFIX%&.
32023 If the permitted configuration files are confined to a directory to
32024 which only root has access, this guards against someone who has broken
32025 into the Exim account from running a privileged Exim with an arbitrary
32026 configuration file, and using it to break into other accounts.
32028 If ALT_CONFIG_ROOT_ONLY is defined, root privilege is retained for &%-C%&
32029 and &%-D%& only if the caller of Exim is root. Without it, the Exim user may
32030 also use &%-C%& and &%-D%& and retain privilege. Setting this option locks out
32031 the possibility of testing a configuration using &%-C%& right through message
32032 reception and delivery, even if the caller is root. The reception works, but by
32033 that time, Exim is running as the Exim user, so when it re-execs to regain
32034 privilege for the delivery, the use of &%-C%& causes privilege to be lost.
32035 However, root can test reception and delivery using two separate commands.
32036 ALT_CONFIG_ROOT_ONLY is not set by default.
32038 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
32041 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
32042 never to be used for any deliveries. This is like the &%never_users%& runtime
32043 option, but it cannot be overridden; the runtime option adds additional users
32044 to the list. The default setting is &"root"&; this prevents a non-root user who
32045 is permitted to modify the runtime file from using Exim as a way to get root.
32051 .section "Root privilege"
32053 .cindex "root privilege"
32054 The Exim binary is normally setuid to root, which means that it gains root
32055 privilege (runs as root) when it starts execution. In some special cases (for
32056 example, when the daemon is not in use and there are no local deliveries), it
32057 may be possible to run Exim setuid to some user other than root. This is
32058 discussed in the next section. However, in most installations, root privilege
32059 is required for two things:
32062 To set up a socket connected to the standard SMTP port (25) when initialising
32063 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
32066 To be able to change uid and gid in order to read users' &_.forward_& files and
32067 perform local deliveries as the receiving user or as specified in the
32071 It is not necessary to be root to do any of the other things Exim does, such as
32072 receiving messages and delivering them externally over SMTP, and it is
32073 obviously more secure if Exim does not run as root except when necessary.
32074 For this reason, a user and group for Exim to use must be defined in
32075 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
32076 group"&. Their values can be changed by the run time configuration, though this
32077 is not recommended. Often a user called &'exim'& is used, but some sites use
32078 &'mail'& or another user name altogether.
32080 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
32081 abdication; the process cannot regain root afterwards. Prior to release 4.00,
32082 &[seteuid()]& was used in some circumstances, but this is no longer the case.
32084 After a new Exim process has interpreted its command line options, it changes
32085 uid and gid in the following cases:
32088 .cindex "&%-C%& option"
32089 .cindex "&%-D%& option"
32090 If the &%-C%& option is used to specify an alternate configuration file, or if
32091 the &%-D%& option is used to define macro values for the configuration, and the
32092 calling process is not running as root or the Exim user, the uid and gid are
32093 changed to those of the calling process.
32094 However, if ALT_CONFIG_ROOT_ONLY is defined in &_Local/Makefile_&, only
32095 root callers may use &%-C%& and &%-D%& without losing privilege, and if
32096 DISABLE_D_OPTION is set, the &%-D%& option may not be used at all.
32098 .cindex "&%-be%& option"
32099 .cindex "&%-bf%& option"
32100 .cindex "&%-bF%& option"
32101 If the expansion test option (&%-be%&) or one of the filter testing options
32102 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
32105 If the process is not a daemon process or a queue runner process or a delivery
32106 process or a process for testing address routing (started with &%-bt%&), the
32107 uid and gid are changed to the Exim user and group. This means that Exim always
32108 runs under its own uid and gid when receiving messages. This also applies when
32109 testing address verification
32110 .cindex "&%-bv%& option"
32111 .cindex "&%-bh%& option"
32112 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
32115 For a daemon, queue runner, delivery, or address testing process, the uid
32116 remains as root at this stage, but the gid is changed to the Exim group.
32119 The processes that initially retain root privilege behave as follows:
32122 A daemon process changes the gid to the Exim group and the uid to the Exim
32123 user after setting up one or more listening sockets. The &[initgroups()]&
32124 function is called, so that if the Exim user is in any additional groups, they
32125 will be used during message reception.
32127 A queue runner process retains root privilege throughout its execution. Its
32128 job is to fork a controlled sequence of delivery processes.
32130 A delivery process retains root privilege throughout most of its execution,
32131 but any actual deliveries (that is, the transports themselves) are run in
32132 subprocesses which always change to a non-root uid and gid. For local
32133 deliveries this is typically the uid and gid of the owner of the mailbox; for
32134 remote deliveries, the Exim uid and gid are used. Once all the delivery
32135 subprocesses have been run, a delivery process changes to the Exim uid and gid
32136 while doing post-delivery tidying up such as updating the retry database and
32137 generating bounce and warning messages.
32139 While the recipient addresses in a message are being routed, the delivery
32140 process runs as root. However, if a user's filter file has to be processed,
32141 this is done in a subprocess that runs under the individual user's uid and
32142 gid. A system filter is run as root unless &%system_filter_user%& is set.
32144 A process that is testing addresses (the &%-bt%& option) runs as root so that
32145 the routing is done in the same environment as a message delivery.
32151 .section "Running Exim without privilege" "SECTrunexiwitpri"
32152 .cindex "privilege" "running without"
32153 .cindex "unprivileged running"
32154 .cindex "root privilege" "running without"
32155 Some installations like to run Exim in an unprivileged state for more of its
32156 operation, for added security. Support for this mode of operation is provided
32157 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
32158 gid are changed to the Exim user and group at the start of a delivery process
32159 (and also queue runner and address testing processes). This means that address
32160 routing is no longer run as root, and the deliveries themselves cannot change
32163 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
32164 that the daemon can still be started in the usual way, and it can respond
32165 correctly to SIGHUP because the re-invocation regains root privilege.
32167 An alternative approach is to make Exim setuid to the Exim user and also setgid
32169 If you do this, the daemon must be started from a root process. (Calling
32170 Exim from a root process makes it behave in the way it does when it is setuid
32171 root.) However, the daemon cannot restart itself after a SIGHUP signal because
32172 it cannot regain privilege.
32174 It is still useful to set &%deliver_drop_privilege%& in this case, because it
32175 stops Exim from trying to re-invoke itself to do a delivery after a message has
32176 been received. Such a re-invocation is a waste of resources because it has no
32179 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
32180 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
32181 to the Exim user seems a clean approach, but there is one complication:
32183 In this style of operation, Exim is running with the real uid and gid set to
32184 those of the calling process, and the effective uid/gid set to Exim's values.
32185 Ideally, any association with the calling process' uid/gid should be dropped,
32186 that is, the real uid/gid should be reset to the effective values so as to
32187 discard any privileges that the caller may have. While some operating systems
32188 have a function that permits this action for a non-root effective uid, quite a
32189 number of them do not. Because of this lack of standardization, Exim does not
32190 address this problem at this time.
32192 For this reason, the recommended approach for &"mostly unprivileged"& running
32193 is to keep the Exim binary setuid to root, and to set
32194 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
32195 be used in the most straightforward way.
32197 If you configure Exim not to run delivery processes as root, there are a
32198 number of restrictions on what you can do:
32201 You can deliver only as the Exim user/group. You should explicitly use the
32202 &%user%& and &%group%& options to override routers or local transports that
32203 normally deliver as the recipient. This makes sure that configurations that
32204 work in this mode function the same way in normal mode. Any implicit or
32205 explicit specification of another user causes an error.
32207 Use of &_.forward_& files is severely restricted, such that it is usually
32208 not worthwhile to include them in the configuration.
32210 Users who wish to use &_.forward_& would have to make their home directory and
32211 the file itself accessible to the Exim user. Pipe and append-to-file entries,
32212 and their equivalents in Exim filters, cannot be used. While they could be
32213 enabled in the Exim user's name, that would be insecure and not very useful.
32215 Unless the local user mailboxes are all owned by the Exim user (possible in
32216 some POP3 or IMAP-only environments):
32219 They must be owned by the Exim group and be writable by that group. This
32220 implies you must set &%mode%& in the appendfile configuration, as well as the
32221 mode of the mailbox files themselves.
32223 You must set &%no_check_owner%&, since most or all of the files will not be
32224 owned by the Exim user.
32226 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
32227 on a newly created mailbox when unprivileged. This also implies that new
32228 mailboxes need to be created manually.
32233 These restrictions severely restrict what can be done in local deliveries.
32234 However, there are no restrictions on remote deliveries. If you are running a
32235 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
32236 gives more security at essentially no cost.
32238 If you are using the &%mua_wrapper%& facility (see chapter
32239 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
32244 .section "Delivering to local files"
32245 Full details of the checks applied by &(appendfile)& before it writes to a file
32246 are given in chapter &<<CHAPappendfile>>&.
32250 .section "IPv4 source routing"
32251 .cindex "source routing" "in IP packets"
32252 .cindex "IP source routing"
32253 Many operating systems suppress IP source-routed packets in the kernel, but
32254 some cannot be made to do this, so Exim does its own check. It logs incoming
32255 IPv4 source-routed TCP calls, and then drops them. Things are all different in
32256 IPv6. No special checking is currently done.
32260 .section "The VRFY, EXPN, and ETRN commands in SMTP"
32261 Support for these SMTP commands is disabled by default. If required, they can
32262 be enabled by defining suitable ACLs.
32267 .section "Privileged users"
32268 .cindex "trusted user"
32269 .cindex "admin user"
32270 .cindex "privileged user"
32271 .cindex "user" "trusted"
32272 .cindex "user" "admin"
32273 Exim recognises two sets of users with special privileges. Trusted users are
32274 able to submit new messages to Exim locally, but supply their own sender
32275 addresses and information about a sending host. For other users submitting
32276 local messages, Exim sets up the sender address from the uid, and doesn't
32277 permit a remote host to be specified.
32279 .cindex "&%-f%& option"
32280 However, an untrusted user is permitted to use the &%-f%& command line option
32281 in the special form &%-f <>%& to indicate that a delivery failure for the
32282 message should not cause an error report. This affects the message's envelope,
32283 but it does not affect the &'Sender:'& header. Untrusted users may also be
32284 permitted to use specific forms of address with the &%-f%& option by setting
32285 the &%untrusted_set_sender%& option.
32287 Trusted users are used to run processes that receive mail messages from some
32288 other mail domain and pass them on to Exim for delivery either locally, or over
32289 the Internet. Exim trusts a caller that is running as root, as the Exim user,
32290 as any user listed in the &%trusted_users%& configuration option, or under any
32291 group listed in the &%trusted_groups%& option.
32293 Admin users are permitted to do things to the messages on Exim's queue. They
32294 can freeze or thaw messages, cause them to be returned to their senders, remove
32295 them entirely, or modify them in various ways. In addition, admin users can run
32296 the Exim monitor and see all the information it is capable of providing, which
32297 includes the contents of files on the spool.
32299 .cindex "&%-M%& option"
32300 .cindex "&%-q%& option"
32301 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
32302 delivery of messages on its queue is restricted to admin users. This
32303 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
32304 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
32305 queue is also restricted to admin users. This restriction can be relaxed by
32306 setting &%no_queue_list_requires_admin%&.
32308 Exim recognises an admin user if the calling process is running as root or as
32309 the Exim user or if any of the groups associated with the calling process is
32310 the Exim group. It is not necessary actually to be running under the Exim
32311 group. However, if admin users who are not root or the Exim user are to access
32312 the contents of files on the spool via the Exim monitor (which runs
32313 unprivileged), Exim must be built to allow group read access to its spool
32318 .section "Spool files"
32319 .cindex "spool directory" "files"
32320 Exim's spool directory and everything it contains is owned by the Exim user and
32321 set to the Exim group. The mode for spool files is defined in the
32322 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
32323 any user who is a member of the Exim group can access these files.
32327 .section "Use of argv[0]"
32328 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
32329 of specific strings, Exim assumes certain options. For example, calling Exim
32330 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
32331 to calling it with the option &%-bS%&. There are no security implications in
32336 .section "Use of %f formatting"
32337 The only use made of &"%f"& by Exim is in formatting load average values. These
32338 are actually stored in integer variables as 1000 times the load average.
32339 Consequently, their range is limited and so therefore is the length of the
32344 .section "Embedded Exim path"
32345 Exim uses its own path name, which is embedded in the code, only when it needs
32346 to re-exec in order to regain root privilege. Therefore, it is not root when it
32347 does so. If some bug allowed the path to get overwritten, it would lead to an
32348 arbitrary program's being run as exim, not as root.
32352 .section "Use of sprintf()"
32353 .cindex "&[sprintf()]&"
32354 A large number of occurrences of &"sprintf"& in the code are actually calls to
32355 &'string_sprintf()'&, a function that returns the result in malloc'd store.
32356 The intermediate formatting is done into a large fixed buffer by a function
32357 that runs through the format string itself, and checks the length of each
32358 conversion before performing it, thus preventing buffer overruns.
32360 The remaining uses of &[sprintf()]& happen in controlled circumstances where
32361 the output buffer is known to be sufficiently long to contain the converted
32366 .section "Use of debug_printf() and log_write()"
32367 Arbitrary strings are passed to both these functions, but they do their
32368 formatting by calling the function &'string_vformat()'&, which runs through
32369 the format string itself, and checks the length of each conversion.
32373 .section "Use of strcat() and strcpy()"
32374 These are used only in cases where the output buffer is known to be large
32375 enough to hold the result.
32376 .ecindex IIDsecurcon
32381 . ////////////////////////////////////////////////////////////////////////////
32382 . ////////////////////////////////////////////////////////////////////////////
32384 .chapter "Format of spool files" "CHAPspool"
32385 .scindex IIDforspo1 "format" "spool files"
32386 .scindex IIDforspo2 "spool directory" "format of files"
32387 .scindex IIDforspo3 "spool files" "format of"
32388 .cindex "spool files" "editing"
32389 A message on Exim's queue consists of two files, whose names are the message id
32390 followed by -D and -H, respectively. The data portion of the message is kept in
32391 the -D file on its own. The message's envelope, status, and headers are all
32392 kept in the -H file, whose format is described in this chapter. Each of these
32393 two files contains the final component of its own name as its first line. This
32394 is insurance against disk crashes where the directory is lost but the files
32395 themselves are recoverable.
32397 Some people are tempted into editing -D files in order to modify messages. You
32398 need to be extremely careful if you do this; it is not recommended and you are
32399 on your own if you do it. Here are some of the pitfalls:
32402 You must ensure that Exim does not try to deliver the message while you are
32403 fiddling with it. The safest way is to take out a write lock on the -D file,
32404 which is what Exim itself does, using &[fcntl()]&. If you update the file in
32405 place, the lock will be retained. If you write a new file and rename it, the
32406 lock will be lost at the instant of rename.
32408 .cindex "&$body_linecount$&"
32409 If you change the number of lines in the file, the value of
32410 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
32411 present, this value is not used by Exim, but there is no guarantee that this
32412 will always be the case.
32414 If the message is in MIME format, you must take care not to break it.
32416 If the message is cryptographically signed, any change will invalidate the
32421 Files whose names end with -J may also be seen in the &_input_& directory (or
32422 its subdirectories when &%split_spool_directory%& is set). These are journal
32423 files, used to record addresses to which the message has been delivered during
32424 the course of a delivery run. At the end of the run, the -H file is updated,
32425 and the -J file is deleted.
32428 .section "Format of the -H file"
32429 .cindex "uid (user id)" "in spool file"
32430 .cindex "gid (group id)" "in spool file"
32431 The second line of the -H file contains the login name for the uid of the
32432 process that called Exim to read the message, followed by the numerical uid and
32433 gid. For a locally generated message, this is normally the user who sent the
32434 message. For a message received over TCP/IP, it is normally the Exim user.
32436 The third line of the file contains the address of the message's sender as
32437 transmitted in the envelope, contained in angle brackets. The sender address is
32438 empty for bounce messages. For incoming SMTP mail, the sender address is given
32439 in the MAIL command. For locally generated mail, the sender address is
32440 created by Exim from the login name of the current user and the configured
32441 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
32442 leading &"From&~"& line if the caller is trusted, or if the supplied address is
32443 &"<>"& or an address that matches &%untrusted_set_senders%&.
32445 The fourth line contains two numbers. The first is the time that the message
32446 was received, in the conventional Unix form &-- the number of seconds since the
32447 start of the epoch. The second number is a count of the number of messages
32448 warning of delayed delivery that have been sent to the sender.
32450 There follow a number of lines starting with a hyphen. These can appear in any
32451 order, and are omitted when not relevant:
32454 .vitem "&%-acl%& <&'number'&> <&'length'&>"
32456 This item is obsolete, and is not generated from Exim release 4.61 onwards;
32457 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
32458 recognized, to provide backward compatibility. In the old format, a line of
32459 this form is present for every ACL variable that is not empty. The number
32460 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
32461 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
32462 the data string for the variable. The string itself starts at the beginning of
32463 the next line, and is followed by a newline character. It may contain internal
32466 .vitem "&%-aclc%& <&'number'&> <&'length'&>"
32467 A line of this form is present for every ACL connection variable that is not
32468 empty. The number identifies the variable. The length is the length of the data
32469 string for the variable. The string itself starts at the beginning of the next
32470 line, and is followed by a newline character. It may contain internal newlines.
32472 .vitem "&%-aclm%& <&'number'&> <&'length'&>"
32473 A line of this form is present for every ACL message variable that is not
32474 empty. The number identifies the variable. The length is the length of the data
32475 string for the variable. The string itself starts at the beginning of the next
32476 line, and is followed by a newline character. It may contain internal newlines.
32479 .vitem "&%-active_hostname%& <&'hostname'&>"
32480 This is present if, when the message was received over SMTP, the value of
32481 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
32483 .vitem &%-allow_unqualified_recipient%&
32484 This is present if unqualified recipient addresses are permitted in header
32485 lines (to stop such addresses from being qualified if rewriting occurs at
32486 transport time). Local messages that were input using &%-bnq%& and remote
32487 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
32489 .vitem &%-allow_unqualified_sender%&
32490 This is present if unqualified sender addresses are permitted in header lines
32491 (to stop such addresses from being qualified if rewriting occurs at transport
32492 time). Local messages that were input using &%-bnq%& and remote messages from
32493 hosts that match &%sender_unqualified_hosts%& set this flag.
32495 .vitem "&%-auth_id%& <&'text'&>"
32496 The id information for a message received on an authenticated SMTP connection
32497 &-- the value of the &$authenticated_id$& variable.
32499 .vitem "&%-auth_sender%& <&'address'&>"
32500 The address of an authenticated sender &-- the value of the
32501 &$authenticated_sender$& variable.
32503 .vitem "&%-body_linecount%& <&'number'&>"
32504 This records the number of lines in the body of the message, and is always
32507 .vitem "&%-body_zerocount%& <&'number'&>"
32508 This records the number of binary zero bytes in the body of the message, and is
32509 present if the number is greater than zero.
32511 .vitem &%-deliver_firsttime%&
32512 This is written when a new message is first added to the spool. When the spool
32513 file is updated after a deferral, it is omitted.
32515 .vitem "&%-frozen%& <&'time'&>"
32516 .cindex "frozen messages" "spool data"
32517 The message is frozen, and the freezing happened at <&'time'&>.
32519 .vitem "&%-helo_name%& <&'text'&>"
32520 This records the host name as specified by a remote host in a HELO or EHLO
32523 .vitem "&%-host_address%& <&'address'&>.<&'port'&>"
32524 This records the IP address of the host from which the message was received and
32525 the remote port number that was used. It is omitted for locally generated
32528 .vitem "&%-host_auth%& <&'text'&>"
32529 If the message was received on an authenticated SMTP connection, this records
32530 the name of the authenticator &-- the value of the
32531 &$sender_host_authenticated$& variable.
32533 .vitem &%-host_lookup_failed%&
32534 This is present if an attempt to look up the sending host's name from its IP
32535 address failed. It corresponds to the &$host_lookup_failed$& variable.
32537 .vitem "&%-host_name%& <&'text'&>"
32538 .cindex "reverse DNS lookup"
32539 .cindex "DNS" "reverse lookup"
32540 This records the name of the remote host from which the message was received,
32541 if the host name was looked up from the IP address when the message was being
32542 received. It is not present if no reverse lookup was done.
32544 .vitem "&%-ident%& <&'text'&>"
32545 For locally submitted messages, this records the login of the originating user,
32546 unless it was a trusted user and the &%-oMt%& option was used to specify an
32547 ident value. For messages received over TCP/IP, this records the ident string
32548 supplied by the remote host, if any.
32550 .vitem "&%-interface_address%& <&'address'&>.<&'port'&>"
32551 This records the IP address of the local interface and the port number through
32552 which a message was received from a remote host. It is omitted for locally
32553 generated messages.
32556 The message is from a local sender.
32558 .vitem &%-localerror%&
32559 The message is a locally-generated bounce message.
32561 .vitem "&%-local_scan%& <&'string'&>"
32562 This records the data string that was returned by the &[local_scan()]& function
32563 when the message was received &-- the value of the &$local_scan_data$&
32564 variable. It is omitted if no data was returned.
32566 .vitem &%-manual_thaw%&
32567 The message was frozen but has been thawed manually, that is, by an explicit
32568 Exim command rather than via the auto-thaw process.
32571 A testing delivery process was started using the &%-N%& option to suppress any
32572 actual deliveries, but delivery was deferred. At any further delivery attempts,
32575 .vitem &%-received_protocol%&
32576 This records the value of the &$received_protocol$& variable, which contains
32577 the name of the protocol by which the message was received.
32579 .vitem &%-sender_set_untrusted%&
32580 The envelope sender of this message was set by an untrusted local caller (used
32581 to ensure that the caller is displayed in queue listings).
32583 .vitem "&%-spam_score_int%& <&'number'&>"
32584 If a message was scanned by SpamAssassin, this is present. It records the value
32585 of &$spam_score_int$&.
32587 .vitem &%-tls_certificate_verified%&
32588 A TLS certificate was received from the client that sent this message, and the
32589 certificate was verified by the server.
32591 .vitem "&%-tls_cipher%& <&'cipher name'&>"
32592 When the message was received over an encrypted connection, this records the
32593 name of the cipher suite that was used.
32595 .vitem "&%-tls_peerdn%& <&'peer DN'&>"
32596 When the message was received over an encrypted connection, and a certificate
32597 was received from the client, this records the Distinguished Name from that
32601 Following the options there is a list of those addresses to which the message
32602 is not to be delivered. This set of addresses is initialized from the command
32603 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
32604 is set; otherwise it starts out empty. Whenever a successful delivery is made,
32605 the address is added to this set. The addresses are kept internally as a
32606 balanced binary tree, and it is a representation of that tree which is written
32607 to the spool file. If an address is expanded via an alias or forward file, the
32608 original address is added to the tree when deliveries to all its child
32609 addresses are complete.
32611 If the tree is empty, there is a single line in the spool file containing just
32612 the text &"XX"&. Otherwise, each line consists of two letters, which are either
32613 Y or N, followed by an address. The address is the value for the node of the
32614 tree, and the letters indicate whether the node has a left branch and/or a
32615 right branch attached to it, respectively. If branches exist, they immediately
32616 follow. Here is an example of a three-node tree:
32618 YY darcy@austen.fict.example
32619 NN alice@wonderland.fict.example
32620 NN editor@thesaurus.ref.example
32622 After the non-recipients tree, there is a list of the message's recipients.
32623 This is a simple list, preceded by a count. It includes all the original
32624 recipients of the message, including those to whom the message has already been
32625 delivered. In the simplest case, the list contains one address per line. For
32629 editor@thesaurus.ref.example
32630 darcy@austen.fict.example
32632 alice@wonderland.fict.example
32634 However, when a child address has been added to the top-level addresses as a
32635 result of the use of the &%one_time%& option on a &(redirect)& router, each
32636 line is of the following form:
32638 <&'top-level address'&> <&'errors_to address'&> &&&
32639 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
32641 The 01 flag bit indicates the presence of the three other fields that follow
32642 the top-level address. Other bits may be used in future to support additional
32643 fields. The <&'parent number'&> is the offset in the recipients list of the
32644 original parent of the &"one time"& address. The first two fields are the
32645 envelope sender that is associated with this address and its length. If the
32646 length is zero, there is no special envelope sender (there are then two space
32647 characters in the line). A non-empty field can arise from a &(redirect)& router
32648 that has an &%errors_to%& setting.
32651 A blank line separates the envelope and status information from the headers
32652 which follow. A header may occupy several lines of the file, and to save effort
32653 when reading it in, each header is preceded by a number and an identifying
32654 character. The number is the number of characters in the header, including any
32655 embedded newlines and the terminating newline. The character is one of the
32659 .row <&'blank'&> "header in which Exim has no special interest"
32660 .row &`B`& "&'Bcc:'& header"
32661 .row &`C`& "&'Cc:'& header"
32662 .row &`F`& "&'From:'& header"
32663 .row &`I`& "&'Message-id:'& header"
32664 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
32665 .row &`R`& "&'Reply-To:'& header"
32666 .row &`S`& "&'Sender:'& header"
32667 .row &`T`& "&'To:'& header"
32668 .row &`*`& "replaced or deleted header"
32671 Deleted or replaced (rewritten) headers remain in the spool file for debugging
32672 purposes. They are not transmitted when the message is delivered. Here is a
32673 typical set of headers:
32675 111P Received: by hobbit.fict.example with local (Exim 4.00)
32676 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
32677 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
32678 038* X-rewrote-sender: bb@hobbit.fict.example
32679 042* From: Bilbo Baggins <bb@hobbit.fict.example>
32680 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
32681 099* To: alice@wonderland.fict.example, rdo@foundation,
32682 darcy@austen.fict.example, editor@thesaurus.ref.example
32683 104T To: alice@wonderland.fict.example, rdo@foundation.example,
32684 darcy@austen.fict.example, editor@thesaurus.ref.example
32685 038 Date: Fri, 11 May 2001 10:28:59 +0100
32687 The asterisked headers indicate that the envelope sender, &'From:'& header, and
32688 &'To:'& header have been rewritten, the last one because routing expanded the
32689 unqualified domain &'foundation'&.
32690 .ecindex IIDforspo1
32691 .ecindex IIDforspo2
32692 .ecindex IIDforspo3
32697 . ////////////////////////////////////////////////////////////////////////////
32698 . ////////////////////////////////////////////////////////////////////////////
32700 .chapter "Adding new drivers or lookup types" "" &&&
32701 "Adding drivers or lookups"
32702 .cindex "adding drivers"
32703 .cindex "new drivers" "adding"
32704 .cindex "drivers" "adding new"
32705 The following actions have to be taken in order to add a new router, transport,
32706 authenticator, or lookup type to Exim:
32709 Choose a name for the driver or lookup type that does not conflict with any
32710 existing name; I will use &"newdriver"& in what follows.
32712 Add to &_src/EDITME_& the line:
32714 <&'type'&>&`_NEWDRIVER=yes`&
32716 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
32717 code is not to be included in the binary by default, comment this line out. You
32718 should also add any relevant comments about the driver or lookup type.
32720 Add to &_src/config.h.defaults_& the line:
32722 #define <type>_NEWDRIVER
32725 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
32726 and create a table entry as is done for all the other drivers and lookup types.
32728 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
32729 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
32730 driver or lookup type and add it to the definition of OBJ.
32732 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
32735 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
32736 as for other drivers and lookups.
32739 Then all you need to do is write the code! A good way to start is to make a
32740 proforma by copying an existing module of the same type, globally changing all
32741 occurrences of the name, and cutting out most of the code. Note that any
32742 options you create must be listed in alphabetical order, because the tables are
32743 searched using a binary chop procedure.
32745 There is a &_README_& file in each of the sub-directories of &_src_& describing
32746 the interface that is expected.
32751 . ////////////////////////////////////////////////////////////////////////////
32752 . ////////////////////////////////////////////////////////////////////////////
32754 .makeindex "Option index" "option"
32756 .makeindex "Concept index" "concept"
32759 . /////////////////////////////////////////////////////////////////////////////
32760 . /////////////////////////////////////////////////////////////////////////////