X-Git-Url: https://git.exim.org/exim-website.git/blobdiff_plain/ad00b118488078f18be87b2f4402481e7bea78d2..c40fd8ce7d6795f2411ff5302550f83160c5e82e:/docbook/4.53/filter.xml diff --git a/docbook/4.53/filter.xml b/docbook/4.53/filter.xml deleted file mode 100644 index 1ec8016..0000000 --- a/docbook/4.53/filter.xml +++ /dev/null @@ -1,2009 +0,0 @@ - - - - - - - -Exim's interfaces to mail filtering -Exim filtering -23 November 2009 -PhilipHazel -PH - - 4.72 - 29 May 2010 - PH - -2009University of Cambridge - - -Forwarding and filtering in Exim - -This document describes the user interfaces to Exim’s in-built mail filtering -facilities, and is copyright © University of Cambridge 2007. It -corresponds to Exim version 4.71. - -
-Introduction - -Most Unix mail transfer agents (programs that deliver mail) permit individual -users to specify automatic forwarding of their mail, usually by placing a list -of forwarding addresses in a file called .forward in their home -directories. Exim extends this facility by allowing the forwarding instructions -to be a set of rules rather than just a list of addresses, in effect providing -.forward with conditions. Operating the set of rules is called -filtering, and the file that contains them is called a filter file. - - -Exim supports two different kinds of filter file. An Exim filter contains -instructions in a format that is unique to Exim. A Sieve filter contains -instructions in the Sieve format that is defined by RFC 3028. As this is a -standard format, Sieve filter files may already be familiar to some users. -Sieve files should also be portable between different environments. However, -the Exim filtering facility contains more features (such as variable -expansion), and better integration with the host environment (such as the use -of external processes and pipes). - - -The choice of which kind of filter to use can be left to the end-user, provided -that the system administrator has configured Exim appropriately for both kinds -of filter. However, if interoperability is important, Sieve is the only -choice. - - -The ability to use filtering or traditional forwarding has to be enabled by the -system administrator, and some of the individual facilities can be separately -enabled or disabled. A local document should be provided to describe exactly -what has been enabled. In the absence of this, consult your system -administrator. - - -This document describes how to use a filter file and the format of its -contents. It is intended for use by end-users. Both Sieve filters and Exim -filters are covered. However, for Sieve filters, only issues that relate to the -Exim implementation are discussed, since Sieve itself is described elsewhere. - - -The contents of traditional .forward files are not described here. They -normally contain just a list of addresses, file names, or pipe commands, -separated by commas or newlines, but other types of item are also available. -The full details can be found in the chapter on the redirect router in the -Exim specification, which also describes how the system administrator can set -up and control the use of filtering. - -
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-Filter operation - -It is important to realize that, in Exim, no deliveries are actually made while -a filter or traditional .forward file is being processed. Running a filter -or processing a traditional .forward file sets up future delivery -operations, but does not carry them out. - - -The result of filter or .forward file processing is a list of destinations -to which a message should be delivered. The deliveries themselves take place -later, along with all other deliveries for the message. This means that it is -not possible to test for successful deliveries while filtering. It also means -that any duplicate addresses that are generated are dropped, because Exim never -delivers the same message to the same address more than once. - -
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-Testing a new filter file - -Filter files, especially the more complicated ones, should always be tested, as -it is easy to make mistakes. Exim provides a facility for preliminary testing -of a filter file before installing it. This tests the syntax of the file and -its basic operation, and can also be used with traditional .forward files. - - -Because a filter can do tests on the content of messages, a test message is -required. Suppose you have a new filter file called myfilter and a test -message in a file called test-message. Assuming that Exim is installed with -the conventional path name /usr/sbin/sendmail (some operating systems use -/usr/lib/sendmail), the following command can be used: - - -/usr/sbin/sendmail -bf myfilter <test-message - - -The option tells Exim that the following item on the command line is -the name of a filter file that is to be tested. There is also a option, -which is similar, but which is used for testing system filter files, as opposed -to user filter files, and which is therefore of use only to the system -administrator. - - -The test message is supplied on the standard input. If there are no -message-dependent tests in the filter, an empty file (/dev/null) can be -used. A supplied message must start with header lines or the From  message -separator line that is found in many multi-message folder files. Note that -blank lines at the start terminate the header lines. A warning is given if no -header lines are read. - - -The result of running this command, provided no errors are detected in the -filter file, is a list of the actions that Exim would try to take if presented -with the message for real. For example, for an Exim filter, the output - - -Deliver message to: gulliver@lilliput.fict.example -Save message to: /home/lemuel/mail/archive - - -means that one copy of the message would be sent to -gulliver@lilliput.fict.example, and another would be added to the file -/home/lemuel/mail/archive, if all went well. - - -The actions themselves are not attempted while testing a filter file in this -way; there is no check, for example, that any forwarding addresses are valid. -For an Exim filter, if you want to know why a particular action is being taken, -add the option to the command. This causes Exim to output the results of -any conditional tests and to indent its output according to the depth of -nesting of if commands. Further additional output from a filter test can be -generated by the testprint command, which is described below. - - -When Exim is outputting a list of the actions it would take, if any text -strings are included in the output, non-printing characters therein are -converted to escape sequences. In particular, if any text string contains a -newline character, this is shown as \n in the testing output. - - -When testing a filter in this way, Exim makes up an envelope for the -message. The recipient is by default the user running the command, and so is -the sender, but the command can be run with the option to supply a -different sender. For example, - - -/usr/sbin/sendmail -bf myfilter \ - -f islington@never.where <test-message - - -Alternatively, if the option is not used, but the first line of the -supplied message is a From  separator from a message folder file (not the -same thing as a From: header line), the sender is taken from there. If - is present, the contents of any From  line are ignored. - - -The return path is the same as the envelope sender, unless the message -contains a Return-path: header, in which case it is taken from there. You -need not worry about any of this unless you want to test out features of a -filter file that rely on the sender address or the return path. - - -It is possible to change the envelope recipient by specifying further options. -The option changes the domain of the recipient address, while the - option changes the local part, that is, the part before the @ -sign. An adviser could make use of these to test someone else’s filter file. - - -The and options specify the prefix or suffix for the local -part. These are relevant only when support for multiple personal mailboxes is -implemented; see the description in section below. - -
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-Installing a filter file - -A filter file is normally installed under the name .forward in your home -directory – it is distinguished from a conventional .forward file by its -first line (described below). However, the file name is configurable, and some -system administrators may choose to use some different name or location for -filter files. - -
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-Testing an installed filter file - -Testing a filter file before installation cannot find every potential problem; -for example, it does not actually run commands to which messages are piped. -Some live tests should therefore also be done once a filter is installed. - - -If at all possible, test your filter file by sending messages from some other -account. If you send a message to yourself from the filtered account, and -delivery fails, the error message will be sent back to the same account, which -may cause another delivery failure. It won’t cause an infinite sequence of such -messages, because delivery failure messages do not themselves generate further -messages. However, it does mean that the failure won’t be returned to you, and -also that the postmaster will have to investigate the stuck message. - - -If you have to test an Exim filter from the same account, a sensible precaution -is to include the line - - -if error_message then finish endif - - -as the first filter command, at least while testing. This causes filtering to -be abandoned for a delivery failure message, and since no destinations are -generated, the message goes on to be delivered to the original address. Unless -there is a good reason for not doing so, it is recommended that the above test -be left in all Exim filter files. (This does not apply to Sieve files.) - -
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-Details of filtering commands - -The filtering commands for Sieve and Exim filters are completely different in -syntax and semantics. The Sieve mechanism is defined in RFC 3028; in the next -chapter we describe how it is integrated into Exim. The subsequent chapter -covers Exim filtering commands in detail. - -
- - - -Sieve filter files - -The code for Sieve filtering in Exim was contributed by Michael Haardt, and -most of the content of this chapter is taken from the notes he provided. Since -Sieve is an extensible language, it is important to understand Sieve in -this context as the specific implementation of Sieve for Exim. - - -This chapter does not contain a description of Sieve, since that can be found -in RFC 3028, which should be read in conjunction with these notes. - - -The Exim Sieve implementation offers the core as defined by RFC 3028, -comparison tests, the subaddress parameter, the copy, envelope, -fileinto, notify, and vacation extensions, but not the reject -extension. Exim does not support message delivery notifications (MDNs), so -adding it just to the Sieve filter (as required for reject) makes little -sense. - - -In order for Sieve to work properly in Exim, the system administrator needs to -make some adjustments to the Exim configuration. These are described in the -chapter on the redirect router in the full Exim specification. - -
-Recognition of Sieve filters - -A filter file is interpreted as a Sieve filter if its first line is - - -# Sieve filter - - -This is what distinguishes it from a conventional .forward file or an Exim -filter file. - -
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-Saving to specified folders - -If the system administrator has set things up as suggested in the Exim -specification, and you use keep or fileinto to save a mail into a -folder, absolute files are stored where specified, relative files are stored -relative to $home, and inbox goes to the standard mailbox location. - -
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-Strings containing header names - -RFC 3028 does not specify what happens if a string denoting a header field does -not contain a valid header name, for example, it contains a colon. This -implementation generates an error instead of ignoring the header field in order -to ease script debugging, which fits in with the common picture of Sieve. - -
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-Exists test with empty list of headers - -The exists test succeeds only if all the specified headers exist. RFC 3028 -does not explicitly specify what happens on an empty list of headers. This -implementation evaluates that condition as true, interpreting the RFC in a -strict sense. - -
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-Header test with invalid MIME encoding in header - -Some MUAs process invalid base64 encoded data, generating junk. Others ignore -junk after seeing an equal sign in base64 encoded data. RFC 2047 does not -specify how to react in this case, other than stating that a client must not -forbid to process a message for that reason. RFC 2045 specifies that invalid -data should be ignored (apparently looking at end of line characters). It also -specifies that invalid data may lead to rejecting messages containing them (and -there it appears to talk about true encoding violations), which is a clear -contradiction to ignoring them. - - -RFC 3028 does not specify how to process incorrect MIME words. This -implementation treats them literally, as it does if the word is correct but its -character set cannot be converted to UTF-8. - -
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-Address test for multiple addresses per header - -A header may contain multiple addresses. RFC 3028 does not explicitly specify -how to deal with them, but since the address test checks if anything matches -anything else, matching one address suffices to satisfy the condition. That -makes it impossible to test if a header contains a certain set of addresses and -no more, but it is more logical than letting the test fail if the header -contains an additional address besides the one the test checks for. - -
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-Semantics of keep - -The keep command is equivalent to - - -fileinto "inbox"; - - -It saves the message and resets the implicit keep flag. It does not set the -implicit keep flag; there is no command to set it once it has been reset. - -
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-Semantics of fileinto - -RFC 3028 does not specify whether fileinto should try to create a mail -folder if it does not exist. This implementation allows the sysadmin to -configure that aspect using the appendfile transport options -, , and . See the -appendfile transport in the Exim specification for details. - -
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-Semantics of redirect - -Sieve scripts are supposed to be interoperable between servers, so this -implementation does not allow mail to be redirected to unqualified addresses, -because the domain would depend on the system being used. On systems with -virtual mail domains, the default domain is probably not what the user expects -it to be. - -
-
-String arguments - -There has been confusion if the string arguments to require are to be -matched case-sensitively or not. This implementation matches them with the -match type :is (default, see section 2.7.1 of the RFC) and the comparator -i;ascii-casemap (default, see section 2.7.3 of the RFC). The RFC defines -the command defaults clearly, so any different implementations violate RFC -3028. The same is valid for comparator names, also specified as strings. - -
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-Number units - -There is a mistake in RFC 3028: the suffix G denotes gibi-, not tebibyte. -The mistake is obvious, because RFC 3028 specifies G to denote 2^30 -(which is gibi, not tebi), and that is what this implementation uses as -the scaling factor for the suffix G. - -
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-RFC compliance - -Exim requires the first line of a Sieve filter to be - - -# Sieve filter - - -Of course the RFC does not specify that line. Do not expect examples to work -without adding it, though. - - -RFC 3028 requires the use of CRLF to terminate a line. The rationale was that -CRLF is universally used in network protocols to mark the end of the line. This -implementation does not embed Sieve in a network protocol, but uses Sieve -scripts as part of the Exim MTA. Since all parts of Exim use LF as the newline -character, this implementation does, too, by default, though the system -administrator may choose (at Exim compile time) to use CRLF instead. - - -Exim violates RFC 2822, section 3.6.8, by accepting 8-bit header names, so this -implementation repeats this violation to stay consistent with Exim. This is in -preparation for UTF-8 data. - - -Sieve scripts cannot contain NUL characters in strings, but mail headers could -contain MIME encoded NUL characters, which could never be matched by Sieve -scripts using exact comparisons. For that reason, this implementation extends -the Sieve quoted string syntax with \0 to describe a NUL character, violating -\0 being the same as 0 in RFC 3028. Even without using \0, the following tests -are all true in this implementation. Implementations that use C-style strings -will only evaluate the first test as true. - - -Subject: =?iso-8859-1?q?abc=00def - -header :contains "Subject" ["abc"] -header :contains "Subject" ["def"] -header :matches "Subject" ["abc?def"] - - -Note that by considering Sieve to be an MUA, RFC 2047 can be interpreted in a -way that NUL characters truncating strings is allowed for Sieve -implementations, although not recommended. It is further allowed to use encoded -NUL characters in headers, but that’s not recommended either. The above example -shows why. - - -RFC 3028 states that if an implementation fails to convert a character set to -UTF-8, two strings cannot be equal if one contains octets greater than 127. -Assuming that all unknown character sets are one-byte character sets with the -lower 128 octets being US-ASCII is not sound, so this implementation violates -RFC 3028 and treats such MIME words literally. That way at least something -could be matched. - - -The folder specified by fileinto must not contain the character sequence -.. to avoid security problems. RFC 3028 does not specify the syntax of -folders apart from keep being equivalent to - - -fileinto "INBOX"; - - -This implementation uses inbox instead. - - -Sieve script errors currently cause messages to be silently filed into -inbox. RFC 3028 requires that the user is notified of that condition. -This may be implemented in the future by adding a header line to mails that -are filed into inbox due to an error in the filter. - -
- - - -Exim filter files - -This chapter contains a full description of the contents of Exim filter files. - -
-Format of Exim filter files - -Apart from leading white space, the first text in an Exim filter file must be - - -# Exim filter - - -This is what distinguishes it from a conventional .forward file or a Sieve -filter file. If the file does not have this initial line (or the equivalent for -a Sieve filter), it is treated as a conventional .forward file, both when -delivering mail and when using the testing mechanism. The white space -in the line is optional, and any capitalization may be used. Further text on -the same line is treated as a comment. For example, you could have - - -# Exim filter <<== do not edit or remove this line! - - -The remainder of the file is a sequence of filtering commands, which consist of -keywords and data values. For example, in the command - - -deliver gulliver@lilliput.fict.example - - -the keyword is deliver and the data value is -gulliver@lilliput.fict.example. White space or line breaks separate the -components of a command, except in the case of conditions for the if -command, where round brackets (parentheses) also act as separators. Complete -commands are separated from each other by white space or line breaks; there are -no special terminators. Thus, several commands may appear on one line, or one -command may be spread over a number of lines. - - -If the character # follows a separator anywhere in a command, everything from -# up to the next newline is ignored. This provides a way of including comments -in a filter file. - -
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-Data values in filter commands - -There are two ways in which a data value can be input: - - - - -If the text contains no white space, it can be typed verbatim. However, if it -is part of a condition, it must also be free of round brackets (parentheses), -as these are used for grouping in conditions. - - - - -Otherwise, text must be enclosed in double quotation marks. In this case, the -character \ (backslash) is treated as an escape character within the -string, causing the following character or characters to be treated specially: - - -\n is replaced by a newline -\r is replaced by a carriage return -\t is replaced by a tab - - - - -Backslash followed by up to three octal digits is replaced by the character -specified by those digits, and \x followed by up to two hexadecimal digits -is treated similarly. Backslash followed by any other character is replaced by -the second character, so that in particular, \" becomes " and \\ -becomes \. A data item enclosed in double quotes can be continued onto the -next line by ending the first line with a backslash. Any leading white space at -the start of the continuation line is ignored. - - -In addition to the escape character processing that occurs when strings are -enclosed in quotes, most data values are also subject to string expansion -(as described in the next section), in which case the characters $ and -\ are also significant. This means that if a single backslash is actually -required in such a string, and the string is also quoted, \\\\ has to be -entered. - - -The maximum permitted length of a data string, before expansion, is 1024 -characters. - -
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-String expansion - -Most data values are expanded before use. Expansion consists of replacing -substrings beginning with $ with other text. The full expansion facilities -available in Exim are extensive. If you want to know everything that Exim can -do with strings, you should consult the chapter on string expansion in the Exim -documentation. - - -In filter files, by far the most common use of string expansion is the -substitution of the contents of a variable. For example, the substring - - -$reply_address - - -is replaced by the address to which replies to the message should be sent. If -such a variable name is followed by a letter or digit or underscore, it must be -enclosed in curly brackets (braces), for example, - - -${reply_address} - - -If a $ character is actually required in an expanded string, it must be -escaped with a backslash, and because backslash is also an escape character in -quoted input strings, it must be doubled in that case. The following two -examples illustrate two different ways of testing for a $ character in a -message: - - -if $message_body contains \$ then ... -if $message_body contains "\\$" then ... - - -You can prevent part of a string from being expanded by enclosing it between -two occurrences of \N. For example, - - -if $message_body contains \N$$$$\N then ... - - -tests for a run of four dollar characters. - -
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-Some useful general variables - -A complete list of the available variables is given in the Exim documentation. -This shortened list contains the ones that are most likely to be useful in -personal filter files: - - -$body_linecount: The number of lines in the body of the message. - - -$body_zerocount: The number of binary zero characters in the body of the -message. - - -$home: In conventional configurations, this variable normally contains the -user’s home directory. The system administrator can, however, change this. - - -$local_part: The part of the email address that precedes the @ sign – -normally the user’s login name. If support for multiple personal mailboxes is -enabled (see section below) and a prefix or suffix for the local -part was recognized, it is removed from the string in this variable. - - -$local_part_prefix: If support for multiple personal mailboxes is enabled -(see section below), and a local part prefix was recognized, -this variable contains the prefix. Otherwise it contains an empty string. - - -$local_part_suffix: If support for multiple personal mailboxes is enabled -(see section below), and a local part suffix was recognized, -this variable contains the suffix. Otherwise it contains an empty string. - - -$message_body: The initial portion of the body of the message. By default, -up to 500 characters are read into this variable, but the system administrator -can configure this to some other value. Newlines in the body are converted into -single spaces. - - -$message_body_end: The final portion of the body of the message, formatted -and limited in the same way as $message_body. - - -$message_body_size: The size of the body of the message, in bytes. - - -$message_exim_id: The message’s local identification string, which is unique -for each message handled by a single host. - - -$message_headers: The header lines of the message, concatenated into a -single string, with newline characters between them. - - -$message_size: The size of the entire message, in bytes. - - -$original_local_part: When an address that arrived with the message is -being processed, this contains the same value as the variable $local_part. -However, if an address generated by an alias, forward, or filter file is being -processed, this variable contains the local part of the original address. - - -$reply_address: The contents of the Reply-to: header, if the message -has one; otherwise the contents of the From: header. It is the address to -which normal replies to the message should be sent. - - -$return_path: The return path – that is, the sender field that will be -transmitted as part of the message’s envelope if the message is sent to another -host. This is the address to which delivery errors are sent. In many cases, -this variable has the same value as $sender_address, but if, for example, -an incoming message to a mailing list has been expanded, $return_path may -have been changed to contain the address of the list maintainer. - - -$sender_address: The sender address that was received in the envelope of -the message. This is not necessarily the same as the contents of the From: -or Sender: header lines. For delivery error messages (bounce messages) -there is no sender address, and this variable is empty. - - -$tod_full: A full version of the time and date, for example: Wed, 18 Oct -1995 09:51:40 +0100. The timezone is always given as a numerical offset from -GMT. - - -$tod_log: The time and date in the format used for writing Exim’s log files, -without the timezone, for example: 1995-10-12 15:32:29. - - -$tod_zone: The local timezone offset, for example: +0100. - -
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-Header variables - -There is a special set of expansion variables containing the header lines of -the message being processed. These variables have names beginning with -$header_ followed by the name of the header line, terminated by a colon. -For example, - - -$header_from: -$header_subject: - - -The whole item, including the terminating colon, is replaced by the contents of -the message header line. If there is more than one header line with the same -name, their contents are concatenated. For header lines whose data consists of -a list of addresses (for example, From: and To:), a comma and newline -is inserted between each set of data. For all other header lines, just a -newline is used. - - -Leading and trailing white space is removed from header line data, and if there -are any MIME words that are encoded as defined by RFC 2047 (because they -contain non-ASCII characters), they are decoded and translated, if possible, to -a local character set. Translation is attempted only on operating systems that -have the iconv() function. This makes the header line look the same as it -would when displayed by an MUA. The default character set is ISO-8859-1, but -this can be changed by means of the headers command (see below). - - -If you want to see the actual characters that make up a header line, you can -specify $rheader_ instead of $header_. This inserts the raw -header line, unmodified. - - -There is also an intermediate form, requested by $bheader_, which removes -leading and trailing space and decodes MIME words, but does not do any -character translation. If an attempt to decode what looks superficially like a -MIME word fails, the raw string is returned. If decoding produces a binary -zero character, it is replaced by a question mark. - - -The capitalization of the name following $header_ is not significant. -Because any printing character except colon may appear in the name of a -message’s header (this is a requirement of RFC 2822, the document that -describes the format of a mail message) curly brackets must not be used in -this case, as they will be taken as part of the header name. Two shortcuts are -allowed in naming header variables: - - - - -The initiating $header_, $rheader_, or $bheader_ can be -abbreviated to $h_, $rh_, or $bh_, respectively. - - - - -The terminating colon can be omitted if the next character is white space. The -white space character is retained in the expanded string. However, this is not -recommended, because it makes it easy to forget the colon when it really is -needed. - - - - -If the message does not contain a header of the given name, an empty string is -substituted. Thus it is important to spell the names of headers correctly. Do -not use $header_Reply_to when you really mean $header_Reply-to. - -
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-User variables - -There are ten user variables with names $n0 – $n9 that can be -incremented by the add command (see section ). These can be -used for scoring messages in various ways. If Exim is configured to run a -system filter on every message, the values left in these variables are -copied into the variables $sn0 – $sn9 at the end of the system filter, -thus making them available to users’ filter files. How these values are used is -entirely up to the individual installation. - -
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-Current directory - -The contents of your filter file should not make any assumptions about the -current directory. It is best to use absolute paths for file names; you can -normally make use of the $home variable to refer to your home directory. The -save command automatically inserts $home at the start of non-absolute -paths. - -
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-Significant deliveries - -When in the course of delivery a message is processed by a filter file, what -happens next, that is, after the filter file has been processed, depends on -whether or not the filter sets up any significant deliveries. If at least -one significant delivery is set up, the filter is considered to have handled -the entire delivery arrangements for the current address, and no further -processing of the address takes place. If, however, no significant deliveries -are set up, Exim continues processing the current address as if there were no -filter file, and typically sets up a delivery of a copy of the message into a -local mailbox. In particular, this happens in the special case of a filter file -containing only comments. - - -The delivery commands deliver, save, and pipe are by default -significant. However, if such a command is preceded by the word unseen, its -delivery is not considered to be significant. In contrast, other commands such -as mail and vacation do not set up significant deliveries unless -preceded by the word seen. The following example commands set up -significant deliveries: - - -deliver jack@beanstalk.example -pipe $home/bin/mymailscript -seen mail subject "message discarded" -seen finish - - -The following example commands do not set up significant deliveries: - - -unseen deliver jack@beanstalk.example -unseen pipe $home/bin/mymailscript -mail subject "message discarded" -finish - -
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-Filter commands - -The filter commands that are described in subsequent sections are listed -below, with the section in which they are described in brackets: - - - - - - - -add -  increment a user variable (section ) - - -deliver -  deliver to an email address (section ) - - -fail -  force delivery failure (sysadmin use) (section ) - - -finish -  end processing (section ) - - -freeze -  freeze message (sysadmin use) (section ) - - -headers -  set the header character set (section ) - - -if -  test condition(s) (section ) - - -logfile -  define log file (section ) - - -logwrite -  write to log file (section ) - - -mail -  send a reply message (section ) - - -pipe -  pipe to a command (section ) - - -save -  save to a file (section ) - - -testprint -  print while testing (section ) - - -vacation -  tailored form of mail (section ) - - - - - -The headers command has additional parameters that can be used only in a -system filter. The fail and freeze commands are available only when -Exim’s filtering facilities are being used as a system filter, and are -therefore usable only by the system administrator and not by ordinary users. -They are mentioned only briefly in this document; for more information, see the -main Exim specification. - -
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-The add command - - add <number> to <user variable> -e.g. add 2 to n3 - - -There are 10 user variables of this type, with names $n0 – $n9. Their -values can be obtained by the normal expansion syntax (for example $n3) in -other commands. At the start of filtering, these variables all contain zero. -Both arguments of the add command are expanded before use, making it -possible to add variables to each other. Subtraction can be obtained by adding -negative numbers. - -
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-The deliver command - - deliver <mail address> -e.g. deliver "Dr Livingstone <David@somewhere.africa.example>" - - -This command provides a forwarding operation. The delivery that it sets up is -significant unless the command is preceded by unseen (see section -). The message is sent on to the given address, exactly as -happens if the address had appeared in a traditional .forward file. If you -want to deliver the message to a number of different addresses, you can use -more than one deliver command (each one may have only one address). -However, duplicate addresses are discarded. - - -To deliver a copy of the message to your normal mailbox, your login name can be -given as the address. Once an address has been processed by the filtering -mechanism, an identical generated address will not be so processed again, so -doing this does not cause a loop. - - -However, if you have a mail alias, you should not refer to it here. For -example, if the mail address L.Gulliver is aliased to lg303 then all -references in Gulliver’s .forward file should be to lg303. A reference -to the alias will not work for messages that are addressed to that alias, -since, like .forward file processing, aliasing is performed only once on an -address, in order to avoid looping. - - -Following the new address, an optional second address, preceded by -errors_to may appear. This changes the address to which delivery errors on -the forwarded message will be sent. Instead of going to the message’s original -sender, they go to this new address. For ordinary users, the only value that is -permitted for this address is the user whose filter file is being processed. -For example, the user lg303 whose mailbox is in the domain -lilliput.example could have a filter file that contains - - -deliver jon@elsewhere.example errors_to lg303@lilliput.example - - -Clearly, using this feature makes sense only in situations where not all -messages are being forwarded. In particular, bounce messages must not be -forwarded in this way, as this is likely to create a mail loop if something -goes wrong. - -
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-The save command - - save <file name> -e.g. save $home/mail/bookfolder - - -This command specifies that a copy of the message is to be appended to the -given file (that is, the file is to be used as a mail folder). The delivery -that save sets up is significant unless the command is preceded by -unseen (see section ). - - -More than one save command may be obeyed; each one causes a copy of the -message to be written to its argument file, provided they are different -(duplicate save commands are ignored). - - -If the file name does not start with a / character, the contents of the -$home variable are prepended, unless it is empty, or the system -administrator has disabled this feature. In conventional configurations, this -variable is normally set in a user filter to the user’s home directory, but the -system administrator may set it to some other path. In some configurations, -$home may be unset, or prepending may be disabled, in which case a -non-absolute path name may be generated. Such configurations convert this to an -absolute path when the delivery takes place. In a system filter, $home is -never set. - - -The user must of course have permission to write to the file, and the writing -of the file takes place in a process that is running as the user, under the -user’s primary group. Any secondary groups to which the user may belong are not -normally taken into account, though the system administrator can configure Exim -to set them up. In addition, the ability to use this command at all is -controlled by the system administrator – it may be forbidden on some systems. - - -An optional mode value may be given after the file name. The value for the mode -is interpreted as an octal number, even if it does not begin with a zero. For -example: - - -save /some/folder 640 - - -This makes it possible for users to override the system-wide mode setting for -file deliveries, which is normally 600. If an existing file does not have the -correct mode, it is changed. - - -An alternative form of delivery may be enabled on your system, in which each -message is delivered into a new file in a given directory. If this is the case, -this functionality can be requested by giving the directory name terminated by -a slash after the save command, for example - - -save separated/messages/ - - -There are several different formats for such deliveries; check with your system -administrator or local documentation to find out which (if any) are available -on your system. If this functionality is not enabled, the use of a path name -ending in a slash causes an error. - -
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-The pipe command - - pipe <command> -e.g. pipe "$home/bin/countmail $sender_address" - - -This command specifies that the message is to be delivered to the specified -command using a pipe. The delivery that it sets up is significant unless the -command is preceded by unseen (see section ). Remember, -however, that no deliveries are done while the filter is being processed. All -deliveries happen later on. Therefore, the result of running the pipe is not -available to the filter. - - -When the deliveries are done, a separate process is run, and a copy of the -message is passed on its standard input. The process runs as the user, under -the user’s primary group. Any secondary groups to which the user may belong are -not normally taken into account, though the system administrator can configure -Exim to set them up. More than one pipe command may appear; each one causes -a copy of the message to be written to its argument pipe, provided they are -different (duplicate pipe commands are ignored). - - -When the time comes to transport the message, the command supplied to pipe -is split up by Exim into a command name and a number of arguments. These are -delimited by white space except for arguments enclosed in double quotes, in -which case backslash is interpreted as an escape, or in single quotes, in which -case no escaping is recognized. Note that as the whole command is normally -supplied in double quotes, a second level of quoting is required for internal -double quotes. For example: - - -pipe "$home/myscript \"size is $message_size\"" - - -String expansion is performed on the separate components after the line has -been split up, and the command is then run directly by Exim; it is not run -under a shell. Therefore, substitution cannot change the number of arguments, -nor can quotes, backslashes or other shell metacharacters in variables cause -confusion. - - -Documentation for some programs that are normally run via this kind of pipe -often suggest that the command should start with - - -IFS=" " - - -This is a shell command, and should not be present in Exim filter files, -since it does not normally run the command under a shell. - - -However, there is an option that the administrator can set to cause a shell to -be used. In this case, the entire command is expanded as a single string and -passed to the shell for interpretation. It is recommended that this be avoided -if at all possible, since it can lead to problems when inserted variables -contain shell metacharacters. - - -The default PATH set up for the command is determined by the system -administrator, usually containing at least /bin and /usr/bin so that -common commands are available without having to specify an absolute file name. -However, it is possible for the system administrator to restrict the pipe -facility so that the command name must not contain any / characters, and must -be found in one of the directories in the configured PATH. It is also possible -for the system administrator to lock out the use of the pipe command -altogether. - - -When the command is run, a number of environment variables are set up. The -complete list for pipe deliveries may be found in the Exim reference manual. -Those that may be useful for pipe deliveries from user filter files are: - - -DOMAIN the domain of the address -HOME your home directory -LOCAL_PART see below -LOCAL_PART_PREFIX see below -LOCAL_PART_SUFFIX see below -LOGNAME your login name -MESSAGE_ID the unique id of the message -PATH the command search path -RECIPIENT the complete recipient address -SENDER the sender of the message -SHELL /bin/sh -USER see below - - -LOCAL_PART, LOGNAME, and USER are all set to the same value, namely, your login -id. LOCAL_PART_PREFIX and LOCAL_PART_SUFFIX may be set if Exim is configured to -recognize prefixes or suffixes in the local parts of addresses. For example, a -message addressed to pat-suf2@domain.example may cause the filter for user -pat to be run. If this sets up a pipe delivery, LOCAL_PART_SUFFIX is --suf2 when the pipe command runs. The system administrator has to configure -Exim specially for this feature to be available. - - -If you run a command that is a shell script, be very careful in your use of -data from the incoming message in the commands in your script. RFC 2822 is very -generous in the characters that are permitted to appear in mail addresses, and -in particular, an address may begin with a vertical bar or a slash. For this -reason you should always use quotes round any arguments that involve data from -the message, like this: - - -/some/command '$SENDER' - - -so that inserted shell meta-characters do not cause unwanted effects. - - -Remember that, as was explained earlier, the pipe command is not run at the -time the filter file is interpreted. The filter just defines what deliveries -are required for one particular addressee of a message. The deliveries -themselves happen later, once Exim has decided everything that needs to be done -for the message. - - -A consequence of this is that you cannot inspect the return code from the pipe -command from within the filter. Nevertheless, the code returned by the command -is important, because Exim uses it to decide whether the delivery has succeeded -or failed. - - -The command should return a zero completion code if all has gone well. Most -non-zero codes are treated by Exim as indicating a failure of the pipe. This is -treated as a delivery failure, causing the message to be returned to its -sender. However, there are some completion codes that are treated as temporary -errors. The message remains on Exim’s spool disk, and the delivery is tried -again later, though it will ultimately time out if the delivery failures go on -too long. The completion codes to which this applies can be specified by the -system administrator; the default values are 73 and 75. - - -The pipe command should not normally write anything to its standard output or -standard error file descriptors. If it does, whatever is written is normally -returned to the sender of the message as a delivery error, though this action -can be varied by the system administrator. - -
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-Mail commands - -There are two commands that cause the creation of a new mail message, neither -of which count as a significant delivery unless the command is preceded by the -word seen (see section ). This is a powerful facility, but -it should be used with care, because of the danger of creating infinite -sequences of messages. The system administrator can forbid the use of these -commands altogether. - - -To help prevent runaway message sequences, these commands have no effect when -the incoming message is a bounce (delivery error) message, and messages sent by -this means are treated as if they were reporting delivery errors. Thus, they -should never themselves cause a bounce message to be returned. The basic -mail-sending command is - - -mail [to <address-list>] - [cc <address-list>] - [bcc <address-list>] - [from <address>] - [reply_to <address>] - [subject <text>] - [extra_headers <text>] - [text <text>] - [[expand] file <filename>] - [return message] - [log <log file name>] - [once <note file name>] - [once_repeat <time interval>] -e.g. mail text "Your message about $h_subject: has been received" - - -Each <address-list> can contain a number of addresses, separated by commas, -in the format of a To: or Cc: header line. In fact, the text you supply -here is copied exactly into the appropriate header line. It may contain -additional information as well as email addresses. For example: - - -mail to "Julius Caesar <jc@rome.example>, \ - <ma@rome.example> (Mark A.)" - - -Similarly, the texts supplied for and are copied into -their respective header lines. - - -As a convenience for use in one common case, there is also a command called -vacation. It behaves in the same way as mail, except that the defaults -for the , , , , and options -are - - -subject "On vacation" -expand file .vacation.msg -log .vacation.log -once .vacation -once_repeat 7d - - -respectively. These are the same file names and repeat period used by the -traditional Unix vacation command. The defaults can be overridden by -explicit settings, but if a file name is given its contents are expanded only -if explicitly requested. - - -Warning: The vacation command should always be used conditionally, -subject to at least the personal condition (see section -below) so as not to send automatic replies to non-personal messages from -mailing lists or elsewhere. Sending an automatic response to a mailing list or -a mailing list manager is an Internet Sin. - - -For both commands, the key/value argument pairs can appear in any order. At -least one of or must appear (except with vacation, where -there is a default for ); if both are present, the text string appears -first in the message. If precedes , each line of the file is -subject to string expansion before it is included in the message. - - -Several lines of text can be supplied to by including the escape -sequence \n in the string wherever a newline is required. If the command is -output during filter file testing, newlines in the text are shown as \n. - - -Note that the keyword for creating a Reply-To: header is , -because Exim keywords may contain underscores, but not hyphens. If the -keyword is present and the given address does not match the user who owns the -forward file, Exim normally adds a Sender: header to the message, though it -can be configured not to do this. - - -The keyword allows you to add custom header lines to the -message. The text supplied must be one or more syntactically valid RFC 2822 -header lines. You can use \n within quoted text to specify newlines between -headers, and also to define continued header lines. For example: - - -extra_headers "h1: first\nh2: second\n continued\nh3: third" - - -No newline should appear at the end of the final header line. - - -If no argument appears, the message is sent to the address in the -$reply_address variable (see section above). -An In-Reply-To: header is automatically included in the created message, -giving a reference to the message identification of the incoming message. - - -If is specified, the incoming message that caused the filter -file to be run is added to the end of the message, subject to a maximum size -limitation. - - -If a log file is specified, a line is added to it for each message sent. - - -If a file is specified, it is used to hold a database for remembering -who has received a message, and no more than one message is ever sent to any -particular address, unless is set. This specifies a time -interval after which another copy of the message is sent. The interval is -specified as a sequence of numbers, each followed by the initial letter of one -of seconds, minutes, hours, days, or weeks. For example, - - -once_repeat 5d4h - - -causes a new message to be sent if at least 5 days and 4 hours have elapsed -since the last one was sent. There must be no white space in a time interval. - - -Commonly, the file name specified for is used as the base name for -direct-access (DBM) file operations. There are a number of different DBM -libraries in existence. Some operating systems provide one as a default, but -even in this case a different one may have been used when building Exim. With -some DBM libraries, specifying results in two files being created, -with the suffixes .dir and .pag being added to the given name. With -some others a single file with the suffix .db is used, or the name is used -unchanged. - - -Using a DBM file for implementing the feature means that the file -grows as large as necessary. This is not usually a problem, but some system -administrators want to put a limit on it. The facility can be configured not to -use a DBM file, but instead, to use a regular file with a maximum size. The -data in such a file is searched sequentially, and if the file fills up, the -oldest entry is deleted to make way for a new one. This means that some -correspondents may receive a second copy of the message after an unpredictable -interval. Consult your local information to see if your system is configured -this way. - - -More than one mail or vacation command may be obeyed in a single filter -run; they are all honoured, even when they are to the same recipient. - -
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-Logging commands - -A log can be kept of actions taken by a filter file. This facility is normally -available in conventional configurations, but there are some situations where -it might not be. Also, the system administrator may choose to disable it. Check -your local information if in doubt. - - -Logging takes place while the filter file is being interpreted. It does not -queue up for later like the delivery commands. The reason for this is so that a -log file need be opened only once for several write operations. There are two -commands, neither of which constitutes a significant delivery. The first -defines a file to which logging output is subsequently written: - - - logfile <file name> -e.g. logfile $home/filter.log - - -The file name must be fully qualified. You can use $home, as in this -example, to refer to your home directory. The file name may optionally be -followed by a mode for the file, which is used if the file has to be created. -For example, - - -logfile $home/filter.log 0644 - - -The number is interpreted as octal, even if it does not begin with a zero. -The default for the mode is 600. It is suggested that the logfile command -normally appear as the first command in a filter file. Once a log file has -been obeyed, the logwrite command can be used to write to it: - - - logwrite "<some text string>" -e.g. logwrite "$tod_log $message_id processed" - - -It is possible to have more than one logfile command, to specify writing to -different log files in different circumstances. Writing takes place at the end -of the file, and a newline character is added to the end of each string if -there isn’t one already there. Newlines can be put in the middle of the string -by using the \n escape sequence. Lines from simultaneous deliveries may get -interleaved in the file, as there is no interlocking, so you should plan your -logging with this in mind. However, data should not get lost. - -
-
-The finish command - -The command finish, which has no arguments, causes Exim to stop -interpreting the filter file. This is not a significant action unless preceded -by seen. A filter file containing only seen finish is a black hole. - -
-
-The testprint command - -It is sometimes helpful to be able to print out the values of variables when -testing filter files. The command - - - testprint <text> -e.g. testprint "home=$home reply_address=$reply_address" - - -does nothing when mail is being delivered. However, when the filtering code is -being tested by means of the option (see section -above), the value of the string is written to the standard output. - -
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-The fail command - -When Exim’s filtering facilities are being used as a system filter, the -fail command is available, to force delivery failure. Because this command -is normally usable only by the system administrator, and not enabled for use by -ordinary users, it is described in more detail in the main Exim specification -rather than in this document. - -
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-The freeze command - -When Exim’s filtering facilities are being used as a system filter, the -freeze command is available, to freeze a message on the queue. Because this -command is normally usable only by the system administrator, and not enabled -for use by ordinary users, it is described in more detail in the main Exim -specification rather than in this document. - -
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-The headers command - -The headers command can be used to change the target character set that is -used when translating the contents of encoded header lines for insertion by the -$header_ mechanism (see section above). The -default can be set in the Exim configuration; if not specified, ISO-8859-1 is -used. The only currently supported format for the headers command in user -filters is as in this example: - - -headers charset "UTF-8" - - -That is, headers is followed by the word charset and then the name of a -character set. This particular example would be useful if you wanted to compare -the contents of a header to a UTF-8 string. - - -In system filter files, the headers command can be used to add or remove -header lines from the message. These features are described in the main Exim -specification. - -
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-Obeying commands conditionally - -Most of the power of filtering comes from the ability to test conditions and -obey different commands depending on the outcome. The if command is used to -specify conditional execution, and its general form is - - -if <condition> -then <commands> -elif <condition> -then <commands> -else <commands> -endif - - -There may be any number of elif and then sections (including none) and -the else section is also optional. Any number of commands, including nested -if commands, may appear in any of the <commands> sections. - - -Conditions can be combined by using the words and and or, and round -brackets (parentheses) can be used to specify how several conditions are to -combine. Without brackets, and is more binding than or. For example: - - -if -$h_subject: contains "Make money" or -$h_precedence: is "junk" or -($h_sender: matches ^\\d{8}@ and not personal) or -$message_body contains "this is not spam" -then -seen finish -endif - - -A condition can be preceded by not to negate it, and there are also some -negative forms of condition that are more English-like. - -
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-String testing conditions - -There are a number of conditions that operate on text strings, using the words -begins, ends, is, contains and matches. If you want to -apply the same test to more than one header line, you can easily concatenate -them into a single string for testing, as in this example: - - -if "$h_to:, $h_cc:" contains me@domain.example then ... - - -If a string-testing condition name is written in lower case, the testing -of letters is done without regard to case; if it is written in upper case -(for example, CONTAINS), the case of letters is taken into account. - - - <text1> begins <text2> - <text1> does not begin <text2> -e.g. $header_from: begins "Friend@" - - -A begins test checks for the presence of the second string at the start of -the first, both strings having been expanded. - - - <text1> ends <text2> - <text1> does not end <text2> -e.g. $header_from: ends "public.com.example" - - -An ends test checks for the presence of the second string at the end of -the first, both strings having been expanded. - - - <text1> is <text2> - <text1> is not <text2> -e.g. $local_part_suffix is "-foo" - - -An is test does an exact match between the strings, having first expanded -both strings. - - - <text1> contains <text2> - <text1> does not contain <text2> -e.g. $header_subject: contains "evolution" - - -A contains test does a partial string match, having expanded both strings. - - - <text1> matches <text2> - <text1> does not match <text2> -e.g. $sender_address matches "(bill|john)@" - - -For a matches test, after expansion of both strings, the second one is -interpreted as a regular expression. Exim uses the PCRE regular expression -library, which provides regular expressions that are compatible with Perl. - - -The match succeeds if the regular expression matches any part of the first -string. If you want a regular expression to match only at the start or end of -the subject string, you must encode that requirement explicitly, using the -^ or $ metacharacters. The above example, which is not so constrained, -matches all these addresses: - - -bill@test.example -john@some.example -spoonbill@example.com -littlejohn@example.com - - -To match only the first two, you could use this: - - -if $sender_address matches "^(bill|john)@" then ... - - -Care must be taken if you need a backslash in a regular expression, because -backslashes are interpreted as escape characters both by the string expansion -code and by Exim’s normal processing of strings in quotes. For example, if you -want to test the sender address for a domain ending in .com the regular -expression is - - -\.com$ - - -The backslash and dollar sign in that expression have to be escaped when used -in a filter command, as otherwise they would be interpreted by the expansion -code. Thus, what you actually write is - - -if $sender_address matches \\.com\$ - - -An alternative way of handling this is to make use of the \N expansion -flag for suppressing expansion: - - -if $sender_address matches \N\.com$\N - - -Everything between the two occurrences of \N is copied without change by -the string expander (and in fact you do not need the final one, because it is -at the end of the string). If the regular expression is given in quotes -(mandatory only if it contains white space) you have to write either - - -if $sender_address matches "\\\\.com\\$" - - -or - - -if $sender_address matches "\\N\\.com$\\N" - - -If the regular expression contains bracketed sub-expressions, numeric -variable substitutions such as $1 can be used in the subsequent actions -after a successful match. If the match fails, the values of the numeric -variables remain unchanged. Previous values are not restored after endif. -In other words, only one set of values is ever available. If the condition -contains several sub-conditions connected by and or or, it is the -strings extracted from the last successful match that are available in -subsequent actions. Numeric variables from any one sub-condition are also -available for use in subsequent sub-conditions, because string expansion of a -condition occurs just before it is tested. - -
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-Numeric testing conditions - -The following conditions are available for performing numerical tests: - - - <number1> is above <number2> - <number1> is not above <number2> - <number1> is below <number2> - <number1> is not below <number2> -e.g. $message_size is not above 10k - - -The <number> arguments must expand to strings of digits, optionally -followed by one of the letters K or M (upper case or lower case) which cause -multiplication by 1024 and 1024x1024 respectively. - -
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-Testing for significant deliveries - -You can use the delivered condition to test whether or not any previously -obeyed filter commands have set up a significant delivery. For example: - - -if not delivered then save mail/anomalous endif - - -Delivered is perhaps a poor choice of name for this condition, because the -message has not actually been delivered; rather, a delivery has been set up for -later processing. - -
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-Testing for error messages - -The condition error_message is true if the incoming message is a bounce -(mail delivery error) message. Putting the command - - -if error_message then finish endif - - -at the head of your filter file is a useful insurance against things going -wrong in such a way that you cannot receive delivery error reports. Note: -error_message is a condition, not an expansion variable, and therefore is -not preceded by $. - -
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-Testing a list of addresses - -There is a facility for looping through a list of addresses and applying a -condition to each of them. It takes the form - - -foranyaddress <string> (<condition>) - - -where <string> is interpreted as a list of RFC 2822 addresses, as in a -typical header line, and <condition> is any valid filter condition or -combination of conditions. The group syntax that is defined for certain -header lines that contain addresses is supported. - - -The parentheses surrounding the condition are mandatory, to delimit it from -possible further sub-conditions of the enclosing if command. Within the -condition, the expansion variable $thisaddress is set to the non-comment -portion of each of the addresses in the string in turn. For example, if the -string is - - -B.Simpson <bart@sfld.example>, lisa@sfld.example (his sister) - - -then $thisaddress would take on the values bart@sfld.example and -lisa@sfld.example in turn. - - -If there are no valid addresses in the list, the whole condition is false. If -the internal condition is true for any one address, the overall condition is -true and the loop ends. If the internal condition is false for all addresses in -the list, the overall condition is false. This example tests for the presence -of an eight-digit local part in any address in a To: header: - - -if foranyaddress $h_to: ( $thisaddress matches ^\\d{8}@ ) then ... - - -When the overall condition is true, the value of $thisaddress in the -commands that follow then is the last value it took on inside the loop. At -the end of the if command, the value of $thisaddress is reset to what it -was before. It is best to avoid the use of multiple occurrences of -foranyaddress, nested or otherwise, in a single if command, if the -value of $thisaddress is to be used afterwards, because it isn’t always -clear what the value will be. Nested if commands should be used instead. - - -Header lines can be joined together if a check is to be applied to more than -one of them. For example: - - -if foranyaddress $h_to:,$h_cc: .... - - -This scans through the addresses in both the To: and the Cc: headers. - -
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-Testing for personal mail - -A common requirement is to distinguish between incoming personal mail and mail -from a mailing list, or from a robot or other automatic process (for example, a -bounce message). In particular, this test is normally required for vacation -messages. - - -The personal condition checks that the message is not a bounce message and -that the current user’s email address appears in the To: header. It also -checks that the sender is not the current user or one of a number of common -daemons, and that there are no header lines starting List- in the message. -Finally, it checks the content of the Precedence: header line, if there is -one. - - -You should always use the personal condition when generating automatic -responses. This example shows the use of personal in a filter file that is -sending out vacation messages: - - -if personal then -mail to $reply_address -subject "I am on holiday" -file $home/vacation/message -once $home/vacation/once -once_repeat 10d -endif - - -It is tempting, when writing commands like the above, to quote the original -subject in the reply. For example: - - -subject "Re: $h_subject:" - - -There is a danger in doing this, however. It may allow a third party to -subscribe you to an opt-in mailing list, provided that the list accepts bounce -messages as subscription confirmations. (Messages sent from filters are always -sent as bounce messages.) Well-managed lists require a non-bounce message to -confirm a subscription, so the danger is relatively small. - - -If prefixes or suffixes are in use for local parts – something which depends -on the configuration of Exim (see section below) – the tests -for the current user are done with the full address (including the prefix and -suffix, if any) as well as with the prefix and suffix removed. If the system is -configured to rewrite local parts of mail addresses, for example, to rewrite -dag46 as Dirk.Gently, the rewritten form of the address is also used in -the tests. - -
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-Alias addresses for the personal condition - -It is quite common for people who have mail accounts on a number of different -systems to forward all their mail to one system, and in this case a check for -personal mail should test all their various mail addresses. To allow for this, -the personal condition keyword can be followed by - - -alias <address> - - -any number of times, for example: - - -if personal alias smith@else.where.example - alias jones@other.place.example -then ... - - -The alias addresses are treated as alternatives to the current user’s email -address when testing the contents of header lines. - -
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-Details of the personal condition - -The basic personal test is roughly equivalent to the following: - - -not error_message and -$message_headers does not contain "\nList-Id:" and -$message_headers does not contain "\nList-Help:" and -$message_headers does not contain "\nList-Subscribe:" and -$message_headers does not contain "\nList-Unsubscribe:" and -$message_headers does not contain "\nList-Post:" and -$message_headers does not contain "\nList-Owner:" and -$message_headers does not contain "\nList-Archive:" and -( -"${if def:h_auto-submitted:{present}{absent}}" is "absent" or -$header_auto-submitted: is "no" -) and -$header_precedence: does not contain "bulk" and -$header_precedence: does not contain "list" and -$header_precedence: does not contain "junk" and -foranyaddress $header_to: -( $thisaddress contains "$local_part$domain" ) and -not foranyaddress $header_from: -( -$thisaddress contains "$local_part@$domain" or -$thisaddress contains "server@" or -$thisaddress contains "daemon@" or -$thisaddress contains "root@" or -$thisaddress contains "listserv@" or -$thisaddress contains "majordomo@" or -$thisaddress contains "-request@" or -$thisaddress matches "^owner-[^@]+@" -) - - -The variable $local_part contains the local part of the mail address of -the user whose filter file is being run – it is normally your login id. The -$domain variable contains the mail domain. As explained above, if aliases -or rewriting are defined, or if prefixes or suffixes are in use, the tests for -the current user are also done with alternative addresses. - -
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-Testing delivery status - -There are two conditions that are intended mainly for use in system filter -files, but which are available in users’ filter files as well. The condition -first_delivery is true if this is the first process that is attempting to -deliver the message, and false otherwise. This indicator is not reset until the -first delivery process successfully terminates; if there is a crash or a power -failure (for example), the next delivery attempt is also a first delivery. - - -In a user filter file first_delivery will be false if there was previously -an error in the filter, or if a delivery for the user failed owing to, for -example, a quota error, or if forwarding to a remote address was deferred for -some reason. - - -The condition manually_thawed is true if the message was frozen for -some reason, and was subsequently released by the system administrator. It is -unlikely to be of use in users’ filter files. - -
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-Multiple personal mailboxes -SEC31 - -The system administrator can configure Exim so that users can set up variants -on their email addresses and handle them separately. Consult your system -administrator or local documentation to see if this facility is enabled on your -system, and if so, what the details are. - - -The facility involves the use of a prefix or a suffix on an email address. For -example, all mail addressed to lg303-<something> would be the property -of user lg303, who could determine how it was to be handled, depending on -the value of <something>. - - -There are two possible ways in which this can be set up. The first possibility -is the use of multiple .forward files. In this case, mail to lg303-foo, -for example, is handled by looking for a file called .forward-foo in -lg303’s home directory. If such a file does not exist, delivery fails -and the message is returned to its sender. - - -The alternative approach is to pass all messages through a single .forward -file, which must be a filter file so that it can distinguish between the -different cases by referencing the variables $local_part_prefix or -$local_part_suffix, as in the final example in section below. - - -It is possible to configure Exim to support both schemes at once. In this case, -a specific .forward-foo file is first sought; if it is not found, the basic -.forward file is used. - - -The personal test (see section ) includes prefixes and -suffixes in its checking. - -
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-Ignoring delivery errors - -As was explained above, filtering just sets up addresses for delivery – no -deliveries are actually done while a filter file is active. If any of the -generated addresses subsequently suffers a delivery failure, an error message -is generated in the normal way. However, if a filter command that sets up a -delivery is preceded by the word noerror, errors for that delivery, -and any deliveries consequent on it (that is, from alias, forwarding, or -filter files it invokes) are ignored. - -
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-Examples of Exim filter commands - -Simple forwarding: - - -# Exim filter -deliver baggins@rivendell.middle-earth.example - - -Vacation handling using traditional means, assuming that the .vacation.msg -and other files have been set up in your home directory: - - -# Exim filter -unseen pipe "/usr/ucb/vacation \"$local_part\"" - - -Vacation handling inside Exim, having first created a file called -.vacation.msg in your home directory: - - -# Exim filter -if personal then vacation endif - - -File some messages by subject: - - -# Exim filter -if $header_subject: contains "empire" or -$header_subject: contains "foundation" -then -save $home/mail/f+e -endif - - -Save all non-urgent messages by weekday: - - -# Exim filter -if $header_subject: does not contain "urgent" and -$tod_full matches "^(...)," -then -save $home/mail/$1 -endif - - -Throw away all mail from one site, except from postmaster: - - -# Exim filter -if $reply_address contains "@spam.site.example" and -$reply_address does not contain "postmaster@" -then -seen finish -endif - - -Handle multiple personal mailboxes: - - -# Exim filter -if $local_part_suffix is "-foo" -then -save $home/mail/foo -elif $local_part_suffix is "-bar" -then -save $home/mail/bar -endif - -
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