| 1 | . $Cambridge: exim/doc/doc-src/filter.src,v 1.1 2004/10/07 15:04:35 ph10 Exp $ |
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| 71 | . ====================================================== |
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| 80 | |
| 81 | |
| 82 | .set chapter -1 |
| 83 | .chapter Exim's interfaces to mail filtering |
| 84 | .space -2ld |
| 85 | Exim is a mail transfer agent for Unix-like systems. This document describes |
| 86 | the user interfaces to its in-built mail filtering facilities, and is copyright |
| 87 | (c) University of Cambridge 2004. It corresponds to Exim version 4.40. |
| 88 | .rule |
| 89 | |
| 90 | . --------------------------------------------------------------------------- |
| 91 | . Some clever jiggery-pokery here. The contents list is known to be less than |
| 92 | . one page long, so we arrange for it to get onto the rest of the first page. |
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| 94 | . the TOC entries. The Makefile arranges for it to be empty at the start, then |
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| 110 | . --------------------------------------------------------------------------- |
| 111 | |
| 112 | |
| 113 | .set chapter 0 |
| 114 | .chapter Forwarding and filtering in Exim |
| 115 | |
| 116 | |
| 117 | .section Introduction |
| 118 | Most Unix mail transfer agents (programs that deliver mail) permit individual |
| 119 | users to specify automatic forwarding of their mail, usually by placing a list |
| 120 | of forwarding addresses in a file called \(.forward)\ in their home directories. |
| 121 | Exim extends this facility by allowing the forwarding instructions to be a set |
| 122 | of rules rather than just a list of addresses, in effect providing `\(.forward)\ |
| 123 | with conditions'. Operating the set of rules is called $it{filtering}, and the |
| 124 | file that contains them is called a $it{filter file}. |
| 125 | |
| 126 | Exim supports two different kinds of filter file. An \*Exim filter*\ contains |
| 127 | instructions in a format that is unique to Exim. A \*Sieve filter*\ contains |
| 128 | instructions in the Sieve format that is defined by RFC 3028. As this is a |
| 129 | standard format, Sieve filter files may already be familiar to some users. |
| 130 | Sieve files should also be portable between different environments. However, |
| 131 | the Exim filtering facility contains more features (such as variable |
| 132 | expansion), and better integration with the host environment (such as the use |
| 133 | of external processes and pipes). |
| 134 | |
| 135 | The choice of which kind of filter to use can be left to the end-user, provided |
| 136 | that the system administrator has configured Exim appropriately for both kinds |
| 137 | of filter. However, if interoperability is important, Sieve is the only |
| 138 | choice. |
| 139 | |
| 140 | The ability to use filtering or traditional forwarding has to be enabled by the |
| 141 | system administrator, and some of the individual facilities can be separately |
| 142 | enabled or disabled. A local document should be provided to describe exactly |
| 143 | what has been enabled. In the absence of this, consult your system |
| 144 | administrator. |
| 145 | |
| 146 | It is important to realize that, in Exim, no deliveries are actually made while |
| 147 | a filter or traditional \(.forward)\ file is being processed. The result of |
| 148 | such processing is a list of destinations to which a message should be |
| 149 | delivered -- the deliveries themselves take place later, along with all other |
| 150 | deliveries for the message. This means that it is not possible to test for |
| 151 | successful deliveries while filtering. It also means that any duplicate |
| 152 | addresses that are generated are dropped, since Exim never delivers the same |
| 153 | message to the same address more than once. |
| 154 | |
| 155 | This document describes how to use a filter file and the format of its |
| 156 | contents. It is intended for use by end-users. Both Sieve filters and Exim |
| 157 | filters are covered. However, for Sieve filters, only issues that relate to the |
| 158 | Exim implementation are discussed, since Sieve itself is described elsewhere. |
| 159 | |
| 160 | The contents of traditional \(.forward)\ files are not described here. They |
| 161 | normally contain just a list of addresses, file names, or pipe commands, |
| 162 | separated by commas or newlines, but other types of item are also available. |
| 163 | The full details can be found in the chapter on the \%redirect%\ router in the |
| 164 | Exim specification, which also describes how the system administrator can set |
| 165 | up and control the use of filtering. |
| 166 | |
| 167 | .section Testing a new filter file |
| 168 | .rset SECTtesting "~~chapter.~~section" |
| 169 | Filter files, especially the more complicated ones, should always be tested, as |
| 170 | it is easy to make mistakes. Exim provides a facility for preliminary testing |
| 171 | of a filter file before installing it. This tests the syntax of the file and |
| 172 | its basic operation, and can also be used with traditional \(.forward)\ files. |
| 173 | |
| 174 | Because a filter can do tests on the content of messages, a test message is |
| 175 | required. Suppose you have a new filter file called \(myfilter)\ and a test |
| 176 | message called \(test-message)\. Assuming that Exim is installed with the |
| 177 | conventional path name \(/usr/sbin/sendmail)\ (some operating systems use |
| 178 | \(/usr/lib/sendmail)\), the following command can be used: |
| 179 | .display asis |
| 180 | /usr/sbin/sendmail -bf myfilter <test-message |
| 181 | .endd |
| 182 | The \-bf-\ option tells Exim that the following item on the command line is the |
| 183 | name of a filter file that is to be tested. There is also a \-bF-\ option, |
| 184 | which is similar, but which is used for testing system filter files, as opposed |
| 185 | to user filter files, and which is therefore of use only to the system |
| 186 | administrator. |
| 187 | |
| 188 | The test message is supplied on the standard input. If there are no |
| 189 | message-dependent tests in the filter, an empty file (\(/dev/null)\) can be |
| 190 | used. A supplied message must start with header lines or the `From' message |
| 191 | separator line which is found in many multi-message folder files. Note that |
| 192 | blank lines at the start terminate the header lines. A warning is given if no |
| 193 | header lines are read. |
| 194 | |
| 195 | The result of running this command, provided no errors are detected in the |
| 196 | filter file, is a list of the actions that Exim would try to take if presented |
| 197 | with the message for real. |
| 198 | For example, for an Exim filter, the output |
| 199 | .display asis |
| 200 | Deliver message to: gulliver@lilliput.fict.example |
| 201 | Save message to: /home/lemuel/mail/archive |
| 202 | .endd |
| 203 | means that one copy of the message would be sent to |
| 204 | \gulliver@@lilliput.fict.example\, and another would be added to the file |
| 205 | \(/home/lemuel/mail/archive)\, if all went well. |
| 206 | |
| 207 | The actions themselves are not attempted while testing a filter file in this |
| 208 | way; there is no check, for example, that any forwarding addresses are valid. |
| 209 | For an Exim filter, |
| 210 | if you want to know why a particular action is being taken, add the \-v-\ |
| 211 | option to the command. This causes Exim to output the results of any |
| 212 | conditional tests and to indent its output according to the depth of nesting of |
| 213 | \"if"\ commands. Further additional output from a filter test can be generated |
| 214 | by the \"testprint"\ command, which is described below. |
| 215 | |
| 216 | When Exim is outputting a list of the actions it would take, if any text |
| 217 | strings are included in the output, non-printing characters therein are |
| 218 | converted to escape sequences. In particular, if any text string contains a |
| 219 | newline character, this is shown as `@\n' in the testing output. |
| 220 | |
| 221 | When testing a filter in this way, Exim makes up an `envelope' for the message. |
| 222 | The recipient is by default the user running the command, and so is the sender, |
| 223 | but the command can be run with the \-f-\ option to supply a different sender. |
| 224 | For example, |
| 225 | .display |
| 226 | .indent 0 |
| 227 | /usr/sbin/sendmail -bf myfilter -f islington@@never.where <test-message |
| 228 | .endd |
| 229 | Alternatively, if the \-f-\ option is not used, but the first line of the |
| 230 | supplied message is a `From' separator from a message folder file (not the same |
| 231 | thing as a \"From:"\ header line), the sender is taken from there. If \-f-\ is |
| 232 | present, the contents of any `From' line are ignored. |
| 233 | |
| 234 | The `return path' is the same as the envelope sender, unless the message |
| 235 | contains a \"Return-path:"\ header, in which case it is taken from there. You |
| 236 | need not worry about any of this unless you want to test out features of a |
| 237 | filter file that rely on the sender address or the return path. |
| 238 | |
| 239 | It is possible to change the envelope recipient by specifying further options. |
| 240 | The \-bfd-\ option changes the domain of the recipient address, while the |
| 241 | \-bfl-\ option changes the `local part', that is, the part before the @@ sign. |
| 242 | An adviser could make use of these to test someone else's filter file. |
| 243 | |
| 244 | The \-bfp-\ and \-bfs-\ options specify the prefix or suffix for the local part. |
| 245 | These are relevant only when support for multiple personal mailboxes is |
| 246 | implemented; see the description in section ~~SECTmbox below. |
| 247 | |
| 248 | .section Installing a filter file |
| 249 | A filter file is normally installed under the name \(.forward)\ in your home |
| 250 | directory -- it is distinguished from a conventional \(.forward)\ file by its |
| 251 | first line (described below). However, the file name is configurable, and some |
| 252 | system administrators may choose to use some different name or location for |
| 253 | filter files. |
| 254 | |
| 255 | .section Testing an installed filter file |
| 256 | Testing a filter file before installation cannot find every potential problem; |
| 257 | for example, it does not actually run commands to which messages are piped. |
| 258 | Some `live' tests should therefore also be done once a filter is installed. |
| 259 | |
| 260 | If at all possible, test your filter file by sending messages from some other |
| 261 | account. If you send a message to yourself from the filtered account, and |
| 262 | delivery fails, the error message will be sent back to the same account, which |
| 263 | may cause another delivery failure. It won't cause an infinite sequence of such |
| 264 | messages, because delivery failure messages do not themselves generate further |
| 265 | messages. However, it does mean that the failure won't be returned to you, and |
| 266 | also that the postmaster will have to investigate the stuck message. |
| 267 | |
| 268 | If you have to test an Exim filter from the same account, a sensible precaution |
| 269 | is to include the line |
| 270 | .display asis |
| 271 | if error_message then finish endif |
| 272 | .endd |
| 273 | as the first filter command, at least while testing. This causes filtering to |
| 274 | be abandoned for a delivery failure message, and since no destinations are |
| 275 | generated, the message goes on to be delivered to the original address. Unless |
| 276 | there is a good reason for not doing so, it is recommended that the above test |
| 277 | be left in all Exim filter files. |
| 278 | (This does not apply to Sieve files.) |
| 279 | |
| 280 | |
| 281 | .section Details of filtering commands |
| 282 | The filtering commands for Sieve and Exim filters are completely different in |
| 283 | syntax and semantics. The Sieve mechanism is defined in RFC 3028; in the next |
| 284 | chapter we describe how it is integrated into Exim. The subsequent chapter |
| 285 | covers Exim filtering commands in detail. |
| 286 | |
| 287 | |
| 288 | . |
| 289 | . |
| 290 | . |
| 291 | . |
| 292 | . |
| 293 | .chapter Sieve filter files |
| 294 | .rset CHAPsievefilter "~~chapter" |
| 295 | The code for Sieve filtering in Exim was contributed by Michael Haardt, and |
| 296 | most of the content of this chapter is taken from the notes he provided. Since |
| 297 | Sieve is a extensible language, it is important to understand `Sieve' in this |
| 298 | context as `the specific implementation of Sieve for Exim'. |
| 299 | |
| 300 | This chapter does not contain a description of Sieve, since that can be found |
| 301 | in RFC 3028, which should be read in conjunction with these notes. |
| 302 | |
| 303 | The Exim Sieve implementation offers the core as defined by RFC 3028, the |
| 304 | \%envelope%\ and the \%fileinto%\ extensions, but not the \%reject%\ extension. |
| 305 | Exim does not support message delivery notifications (MDNs), so adding it just |
| 306 | to the Sieve filter (as required for \%reject%\) makes little sense. |
| 307 | |
| 308 | In order for Sieve to work properly in Exim, the system administrator needs to |
| 309 | make some adjustments to the Exim configuration. These are described in the |
| 310 | chapter on the \%redirect%\ router in the full Exim specification. |
| 311 | |
| 312 | .section Recognition of Sieve filters |
| 313 | A filter file is interpreted as a Sieve filter if its first line is |
| 314 | .display asis |
| 315 | # Sieve filter |
| 316 | .endd |
| 317 | This is what distinguishes it from a conventional \(.forward)\ file or an Exim |
| 318 | filter file. |
| 319 | |
| 320 | |
| 321 | .section Saving to specified folders |
| 322 | If the system administrator has set things up as suggested in the Exim |
| 323 | specification, and you use \%keep%\ or \%fileinto%\ to save a mail into a |
| 324 | folder, absolute files are stored where specified, relative files are stored |
| 325 | relative to \$home$\, and \%inbox%\ goes to the standard mailbox location. |
| 326 | |
| 327 | |
| 328 | .section Strings containing header names |
| 329 | RFC 3028 does not specify what happens if a string denoting a header field does |
| 330 | not contain a valid header name, for example, it contains a colon. This |
| 331 | implementation generates an error instead of ignoring the header field in order |
| 332 | to ease script debugging, which fits in the common picture of Sieve. |
| 333 | |
| 334 | |
| 335 | .section Exists test with empty list of headers |
| 336 | The \%exists%\ test succeeds only if all specified headers exist. RFC 3028 |
| 337 | does not explicitly specify what happens on an empty list of headers. This |
| 338 | implementation evaluates that condition as true, interpreting the RFC in a |
| 339 | strict sense. |
| 340 | |
| 341 | |
| 342 | .section Header test with invalid MIME encoding in header |
| 343 | Some MUAs process invalid base64 encoded data, generating junk. |
| 344 | Others ignore junk after seeing an equal sign in base64 encoded data. |
| 345 | RFC 2047 does not specify how to react in this case, other than stating |
| 346 | that a client must not forbid to process a message for that reason. |
| 347 | RFC 2045 specifies that invalid data should be ignored (apparently |
| 348 | looking at end of line characters). It also specifies that invalid data |
| 349 | may lead to rejecting messages containing them (and there it appears to |
| 350 | talk about true encoding violations), which is a clear contradiction to |
| 351 | ignoring them. |
| 352 | |
| 353 | RFC 3028 does not specify how to process incorrect MIME words. |
| 354 | This implementation treats them literally, as it does if the word is |
| 355 | correct but its character set cannot be converted to UTF-8. |
| 356 | |
| 357 | |
| 358 | .section Address test for multiple addresses per header |
| 359 | A header may contain multiple addresses. RFC 3028 does not explicitly |
| 360 | specify how to deal with them, but since the address test checks if |
| 361 | anything matches anything else, matching one address suffices to |
| 362 | satisfy the condition. That makes it impossible to test if a header |
| 363 | contains a certain set of addresses and no more, but it is more logical |
| 364 | than letting the test fail if the header contains an additional address |
| 365 | besides the one the test checks for. |
| 366 | |
| 367 | |
| 368 | .section Semantics of keep |
| 369 | The \%keep%\ command is equivalent to |
| 370 | .display |
| 371 | fileinto "inbox"; |
| 372 | .endd |
| 373 | It saves the message and resets the implicit keep flag. It does not set the |
| 374 | implicit keep flag; there is no command to set it once it has been reset. |
| 375 | |
| 376 | |
| 377 | .section Semantics of fileinto |
| 378 | RFC 3028 does not specify whether \fileinto\ should try to create a mail folder |
| 379 | if it does not exist. This implementation allows the sysadmin to configure that |
| 380 | aspect using the \%appendfile%\ transport options \create@_directory\, |
| 381 | \create@_file\, and \file@_must@_exist\. See the \%appendfile%\ transport in |
| 382 | the Exim specification for details. |
| 383 | |
| 384 | |
| 385 | .section Semantics of redirect |
| 386 | Sieve scripts are supposed to be interoperable between servers, so this |
| 387 | implementation does not allow mail to be redirected to unqualified addresses, |
| 388 | because the domain would depend on the system being used. On systems with |
| 389 | virtual mail domains, the default domain is probably not what the user expects |
| 390 | it to be. |
| 391 | |
| 392 | |
| 393 | .section String arguments |
| 394 | There has been confusion if the string arguments to \%require%\ are to be |
| 395 | matched case-sensitively or not. This implementation matches them with |
| 396 | the match type \":is"\ (default, see section 2.7.1) and the comparator |
| 397 | \"i;ascii-casemap"\ (default, see section 2.7.3). The RFC defines the |
| 398 | command defaults clearly, so any different implementations violate RFC |
| 399 | 3028. The same is valid for comparator names, also specified as strings. |
| 400 | |
| 401 | |
| 402 | .section Number units |
| 403 | There is a mistake in RFC 3028: the suffix G denotes gibi-, not tebibyte. |
| 404 | The mistake is obvious, because RFC 3028 specifies G to denote 2@^30 |
| 405 | (which is gibi, not tebi), and that is what this implementation uses as |
| 406 | scaling factor for the suffix G. |
| 407 | |
| 408 | |
| 409 | .section RFC compliance |
| 410 | Exim requires the first line of a Sieve filter to be |
| 411 | .display asis |
| 412 | # Sieve filter |
| 413 | .endd |
| 414 | Of course the RFC does not specify that line. Do not expect examples to work |
| 415 | without adding it, though. |
| 416 | |
| 417 | RFC 3028 requires the use of CRLF to terminate a line. |
| 418 | The rationale was that CRLF is universally used in network protocols |
| 419 | to mark the end of the line. This implementation does not embed Sieve |
| 420 | in a network protocol, but uses Sieve scripts as part of the Exim MTA. |
| 421 | Since all parts of Exim use LF as newline character, this implementation |
| 422 | does, too, by default, though the system administrator may choose (at Exim |
| 423 | compile time) to use CRLF instead. |
| 424 | |
| 425 | Exim violates RFC 2822, section 3.6.8, by accepting 8-bit header names, so |
| 426 | this implementation repeats this violation to stay consistent with Exim. |
| 427 | This is in preparation to UTF-8 data. |
| 428 | |
| 429 | Sieve scripts cannot contain NUL characters in strings, but mail |
| 430 | headers could contain MIME encoded NUL characters, which could never |
| 431 | be matched by Sieve scripts using exact comparisons. For that reason, |
| 432 | this implementation extends the Sieve quoted string syntax with @\0 |
| 433 | to describe a NUL character, violating @\0 being the same as 0 in |
| 434 | RFC 3028. Even without using @\0, the following tests are all true in |
| 435 | this implementation. Implementations that use C-style strings will only |
| 436 | evaluate the first test as true. |
| 437 | .display asis |
| 438 | Subject: =?iso-8859-1?q?abc=00def |
| 439 | |
| 440 | header :contains "Subject" ["abc"] |
| 441 | header :contains "Subject" ["def"] |
| 442 | header :matches "Subject" ["abc?def"] |
| 443 | .endd |
| 444 | |
| 445 | Note that by considering Sieve to be a MUA, RFC 2047 can be interpreted |
| 446 | in a way that NUL characters truncating strings is allowed for Sieve |
| 447 | implementations, although not recommended. It is further allowed to use |
| 448 | encoded NUL characters in headers, but that's not recommended either. |
| 449 | The above example shows why. |
| 450 | |
| 451 | RFC 3028 states that if an implementation fails to convert a character |
| 452 | set to UTF-8, two strings cannot be equal if one contains octets greater |
| 453 | than 127. Assuming that all unknown character sets are one-byte character |
| 454 | sets with the lower 128 octets being US-ASCII is not sound, so this |
| 455 | implementation violates RFC 3028 and treats such MIME words literally. |
| 456 | That way at least something could be matched. |
| 457 | |
| 458 | The folder specified by \%fileinto%\ must not contain the character |
| 459 | sequence \".."\ to avoid security problems. RFC 3028 does not specify the |
| 460 | syntax of folders apart from \%keep%\ being equivalent to |
| 461 | .display asis |
| 462 | fileinto "INBOX"; |
| 463 | .endd |
| 464 | This implementation uses \"inbox"\ instead. |
| 465 | |
| 466 | Sieve script errors currently cause messages to be silently filed into |
| 467 | \"inbox"\. RFC 3028 requires that the user is notified of that condition. |
| 468 | This may be implemented in future by adding a header line to mails that |
| 469 | are filed into \"inbox"\ due to an error in the filter. |
| 470 | |
| 471 | |
| 472 | . |
| 473 | . |
| 474 | . |
| 475 | . |
| 476 | . |
| 477 | .chapter Exim filter files |
| 478 | .rset CHAPeximfilter "~~chapter" |
| 479 | This chapter contains a full description of the contents of Exim filter files. |
| 480 | |
| 481 | .section Format of Exim filter files |
| 482 | Apart from leading white space, the first text in a filter file must be |
| 483 | .display asis |
| 484 | # Exim filter |
| 485 | .endd |
| 486 | This is what distinguishes it from a conventional \(.forward)\ file or a Sieve |
| 487 | filter file. If the file does not have this initial line (or the equivalent for |
| 488 | a Sieve filter), it is treated as a |
| 489 | conventional \(.forward)\ file, both when delivering mail and when using the |
| 490 | \-bf-\ testing mechanism. The white space in the line is optional, and any |
| 491 | capitalization may be used. Further text on the same line is treated as a |
| 492 | comment. For example, you could have |
| 493 | .display asis |
| 494 | # Exim filter <<== do not edit or remove this line! |
| 495 | .endd |
| 496 | The remainder of the file is a sequence of filtering commands, which consist of |
| 497 | keywords and data values. For example, in the command |
| 498 | .display asis |
| 499 | deliver gulliver@lilliput.fict.example |
| 500 | .endd |
| 501 | the keyword is \"deliver"\ and the data value is |
| 502 | \"gulliver@@lilliput.fict.example"\. |
| 503 | White space or line breaks separate the components of a command, except in the |
| 504 | case of conditions for the \"if"\ command, where round brackets (parentheses) |
| 505 | also act as separators. Complete commands are separated from each other by |
| 506 | white space or line breaks; there are no special terminators. Thus, several |
| 507 | commands may appear on one line, or one command may be spread over a number of |
| 508 | lines. |
| 509 | |
| 510 | If the character @# follows a separator anywhere in a command, everything from |
| 511 | @# up to the next newline is ignored. This provides a way of including comments |
| 512 | in a filter file. |
| 513 | |
| 514 | .section Data values in filter commands |
| 515 | There are two ways in which a data value can be input: |
| 516 | .numberpars $. |
| 517 | If the text contains no white space then it can be typed verbatim. However, if |
| 518 | it is part of a condition, it must also be free of round brackets |
| 519 | (parentheses), as these are used for grouping in conditions. |
| 520 | .nextp |
| 521 | Otherwise, it must be enclosed in double quotation marks. In this case, the |
| 522 | character @\ (backslash) is treated as an `escape character' within the string, |
| 523 | causing the following character or characters to be treated specially: |
| 524 | .display rm |
| 525 | .tabs 8 |
| 526 | @\n $t is replaced by a newline |
| 527 | @\r $t is replaced by a carriage return |
| 528 | @\t $t is replaced by a tab |
| 529 | .endd |
| 530 | Backslash followed by up to three octal digits is replaced by the character |
| 531 | specified by those digits, and @\x followed by up to two hexadecimal digits is |
| 532 | treated similarly. Backslash followed by any other character is replaced |
| 533 | by the second character, so that in particular, @\" becomes " and @\@\ becomes |
| 534 | @\$<. A data item enclosed in double quotes can be continued onto the next line |
| 535 | by ending the first line with a backslash. Any leading white space at the start |
| 536 | of the continuation line is ignored. |
| 537 | .endp |
| 538 | In addition to the escape character processing that occurs when strings are |
| 539 | enclosed in quotes, most data values are also subject to $it{string expansion} |
| 540 | (as described in the next section), in which case the characters \@$\ and \@\\ |
| 541 | are also significant. This means that if a single backslash is actually |
| 542 | required in such a string, and the string is also quoted, @\@\@\@\ has to be |
| 543 | entered. |
| 544 | |
| 545 | The maximum permitted length of a data string, before expansion, is 1024 |
| 546 | characters. |
| 547 | |
| 548 | |
| 549 | .section String expansion |
| 550 | .rset SECTfilterstringexpansion "~~chapter.~~section" |
| 551 | Most data values are expanded before use. Expansion consists of replacing |
| 552 | substrings beginning with \"@$"\ with other text. The full expansion facilities |
| 553 | available in Exim are extensive. If you want to know everything that Exim can |
| 554 | do with strings, you should consult the chapter on string expansion in the Exim |
| 555 | documentation. |
| 556 | |
| 557 | In filter files, by far the most common use of string expansion is the |
| 558 | substitution of the contents of a variable. For example, the substring |
| 559 | .display asis |
| 560 | $reply_address |
| 561 | .endd |
| 562 | is replaced by the address to which replies to the message should be sent. If |
| 563 | such a variable name is followed by a letter or digit or underscore, it must be |
| 564 | enclosed in curly brackets (braces), for example, |
| 565 | .display asis |
| 566 | ${reply_address} |
| 567 | .endd |
| 568 | If a \"@$"\ character is actually required in an expanded string, it must be |
| 569 | escaped with a backslash, and because backslash is also an escape character in |
| 570 | quoted input strings, it must be doubled in that case. The following two |
| 571 | examples illustrate two different ways of testing for a \"@$"\ character in a |
| 572 | message: |
| 573 | .display asis |
| 574 | if $message_body contains \$ then ... |
| 575 | if $message_body contains "\\$" then ... |
| 576 | .endd |
| 577 | You can prevent part of a string from being expanded by enclosing it between |
| 578 | two occurrences of \"@\N"\. For example, |
| 579 | .display asis |
| 580 | if $message_body contains \N$$$$\N then ... |
| 581 | .endd |
| 582 | tests for a run of four dollar characters. |
| 583 | |
| 584 | .section Some useful general variables |
| 585 | A complete list of the available variables is given in the Exim documentation. |
| 586 | This shortened list contains the ones that are most likely to be useful in |
| 587 | personal filter files: |
| 588 | |
| 589 | \$body@_linecount$\: The number of lines in the body of the message. |
| 590 | |
| 591 | \$home$\: In conventional configurations, this variable normally contains the |
| 592 | user's home directory. The system administrator can, however, change this. |
| 593 | |
| 594 | \$local@_part$\: The part of the email address that precedes the @@ sign -- |
| 595 | normally the user's login name. If support for multiple personal mailboxes is |
| 596 | enabled (see section ~~SECTmbox below) and a prefix or suffix for the local |
| 597 | part was recognized, it is removed from the string in this variable. |
| 598 | |
| 599 | \$local@_part@_prefix$\: If support for multiple personal mailboxes is enabled |
| 600 | (see section ~~SECTmbox below), and a local part prefix was recognized, |
| 601 | this variable contains the prefix. Otherwise it contains an empty string. |
| 602 | |
| 603 | \$local@_part@_suffix$\: If support for multiple personal mailboxes is enabled |
| 604 | (see section ~~SECTmbox below), and a local part suffix was recognized, |
| 605 | this variable contains the suffix. Otherwise it contains an empty string. |
| 606 | |
| 607 | \$message@_body$\: The initial portion of the body of the message. By default, |
| 608 | up to 500 characters are read into this variable, but the system administrator |
| 609 | can configure this to some other value. Newlines in the body are converted into |
| 610 | single spaces. |
| 611 | |
| 612 | \$message@_body@_end$\: The final portion of the body of the message, formatted |
| 613 | and limited in the same way as \$message@_body$\. |
| 614 | |
| 615 | \$message@_body@_size$\: The size of the body of the message, in bytes. |
| 616 | |
| 617 | \$message@_headers$\: The header lines of the message, concatenated into a |
| 618 | single string, with newline characters between them. |
| 619 | |
| 620 | \$message@_id$\: The message's local identification string, which is unique for |
| 621 | each message handled by a single host. |
| 622 | |
| 623 | \$message@_size$\: The size of the entire message, in bytes. |
| 624 | |
| 625 | \$original@_local@_part$\: When an address that arrived with the message is |
| 626 | being processed, this contains the same value as the variable \$local@_part$\. |
| 627 | However, if an address generated by an alias, forward, or filter file is being |
| 628 | processed, this variable contains the local part of the original address. |
| 629 | |
| 630 | \$reply@_address$\: The contents of the \"Reply-to:"\ header, if the message |
| 631 | has one; otherwise the contents of the \"From:"\ header. It is the address to |
| 632 | which normal replies to the message should be sent. |
| 633 | |
| 634 | \$return@_path$\: The return path -- that is, the sender field that will be |
| 635 | transmitted as part of the message's envelope if the message is sent to another |
| 636 | host. This is the address to which delivery errors are sent. In many cases, |
| 637 | this variable has the same value as \$sender@_address$\, but if, for example, |
| 638 | an incoming message to a mailing list has been expanded, \$return@_path$\ may |
| 639 | have been changed to contain the address of the list maintainer. |
| 640 | |
| 641 | \$sender@_address$\: The sender address that was received in the envelope of |
| 642 | the message. This is not necessarily the same as the contents of the \"From:"\ |
| 643 | or \"Sender:"\ header lines. For delivery error messages (`bounce messages') |
| 644 | there is no sender address, and this variable is empty. |
| 645 | |
| 646 | \$tod@_full$\: A full version of the time and date, for example: Wed, 18 Oct |
| 647 | 1995 09:51:40 +0100. The timezone is always given as a numerical offset from |
| 648 | GMT. |
| 649 | |
| 650 | \$tod@_log$\: The time and date in the format used for writing Exim's log files, |
| 651 | without the timezone, for example: 1995-10-12 15:32:29. |
| 652 | |
| 653 | \$tod@_zone$\: The local timezone offset, for example: +0100. |
| 654 | |
| 655 | |
| 656 | .section Header variables |
| 657 | .rset SECTheadervariables "~~chapter.~~section" |
| 658 | There is a special set of expansion variables containing the header lines of |
| 659 | the message being processed. These variables have names beginning with |
| 660 | \"@$header@_"\ followed by the name of the header line, terminated by a colon. |
| 661 | For example, |
| 662 | .display asis |
| 663 | $header_from: |
| 664 | $header_subject: |
| 665 | .endd |
| 666 | The whole item, including the terminating colon, is replaced by the contents of |
| 667 | the message header line. If there is more than one header line with the same |
| 668 | name, their contents are concatenated. For header lines whose data consists of |
| 669 | a list of addresses (for example, ::From:: and ::To::), a comma and newline is |
| 670 | inserted between each set of data. For all other header lines, just a newline |
| 671 | is used. |
| 672 | |
| 673 | Leading and trailing white space is removed from header line data, and if there |
| 674 | are any MIME `words' that are encoded as defined by RFC 2047 (because they |
| 675 | contain non-ASCII characters), they are decoded and translated, if possible, to |
| 676 | a local character set. Translation is attempted only on operating systems that |
| 677 | have the \iconv(@)\ function. This makes the header line look the same as it |
| 678 | would when displayed by an MUA. The default character set is ISO-8859-1, but |
| 679 | this can be changed by means of the \"headers"\ command (see below). |
| 680 | |
| 681 | If you want to see the actual characters that make up a header line, you can |
| 682 | specify \"@$rheader@_"\ instead of \"@$header@_"\. This inserts the `raw' |
| 683 | header line, unmodified. |
| 684 | |
| 685 | There is also an intermediate form, requested by \"@$bheader@_"\, which removes |
| 686 | leading and trailing space and decodes MIME `words', but does not do any |
| 687 | character translation. If an attempt to decode what looks superficially like a |
| 688 | MIME `word' fails, the raw string is returned. If decoding produces a binary |
| 689 | zero character, it is replaced by a question mark. |
| 690 | |
| 691 | The capitalization of the name following \"@$header@_"\ is not significant. |
| 692 | Because any printing character except colon may appear in the name of a |
| 693 | message's header (this is a requirement of RFC 2822, the document that |
| 694 | describes the format of a mail message) curly brackets must $it{not} be used in |
| 695 | this case, as they will be taken as part of the header name. Two shortcuts are |
| 696 | allowed in naming header variables: |
| 697 | .numberpars $. |
| 698 | The initiating \"@$header@_"\, \"@$rheader@_"\, or \"@$bheader@_"\ can be |
| 699 | abbreviated to \"@$h@_"\, \"@$rh@_"\, or \"@$bh@_"\, respectively. |
| 700 | .nextp |
| 701 | The terminating colon can be omitted if the next character is white space. The |
| 702 | white space character is retained in the expanded string. However, this is not |
| 703 | recommended, because it makes it easy to forget the colon when it really is |
| 704 | needed. |
| 705 | .endp |
| 706 | If the message does not contain a header of the given name, an empty string is |
| 707 | substituted. Thus it is important to spell the names of headers correctly. Do |
| 708 | not use \"@$header@_Reply@_to"\ when you really mean \"@$header@_Reply-to"\. |
| 709 | |
| 710 | .section User variables |
| 711 | There are ten user variables with names \$n0$\ -- \$n9$\ that can be |
| 712 | incremented by the \"add"\ command (see section ~~SECTadd). These can be used |
| 713 | for `scoring' messages in various ways. If Exim is configured to run a `system |
| 714 | filter' on every message, the values left in these variables are copied into |
| 715 | the variables \$sn0$\ -- \$sn9$\ at the end of the system filter, thus making |
| 716 | them available to users' filter files. How these values are used is entirely up |
| 717 | to the individual installation. |
| 718 | |
| 719 | .section Current directory |
| 720 | The contents of your filter file should not make any assumptions about the |
| 721 | current directory. It is best to use absolute paths for file names; you |
| 722 | can normally make use of the \$home$\ variable to refer to your home directory. |
| 723 | The \save\ command automatically inserts \$home$\ at the start of non-absolute |
| 724 | paths. |
| 725 | |
| 726 | |
| 727 | |
| 728 | .section Significant deliveries |
| 729 | When in the course of delivery a message is processed by a filter file, what |
| 730 | happens next, that is, after the whole filter file has been processed, depends |
| 731 | on whether the filter has set up any $it{significant deliveries} or not. If |
| 732 | there is at least one significant delivery, the filter is considered to |
| 733 | have handled the entire delivery arrangements for the current address, and no |
| 734 | further processing of the address takes place. If, however, no significant |
| 735 | deliveries have been set up, Exim continues processing the current address as |
| 736 | if there were no filter file, and typically sets up a delivery of a copy of the |
| 737 | message into a local mailbox. In particular, this happens in the special case |
| 738 | of a filter file containing only comments. |
| 739 | |
| 740 | The delivery commands \"deliver"\, \"save"\, and \"pipe"\ are by default |
| 741 | significant. However, if such a command is preceded by the word \"unseen"\, its |
| 742 | delivery is not considered to be significant. In contrast, other commands such |
| 743 | as \"mail"\ and \"vacation"\ do not count as significant deliveries unless |
| 744 | preceded by the word \"seen"\. |
| 745 | |
| 746 | |
| 747 | .section Filter commands |
| 748 | The filter commands which are described in subsequent sections are listed |
| 749 | below, with the section in which they are described in brackets: |
| 750 | .display rm |
| 751 | .tabs 15 |
| 752 | \add\ $t increment a user variable (section ~~SECTadd) |
| 753 | \deliver\ $t deliver to an email address (section ~~SECTdeliver) |
| 754 | \fail\ $t force delivery failure (sysadmin use) (section ~~SECTfail) |
| 755 | \finish\ $t end processing (section ~~SECTfinish) |
| 756 | \freeze\ $t freeze message (sysadmin use) (section ~~SECTfreeze) |
| 757 | \headers\ $t set the header character set (section ~~SECTheaders) |
| 758 | \if\ $t test condition(s) (section ~~SECTif) |
| 759 | \logfile\ $t define log file (section ~~SECTlog) |
| 760 | \logwrite\ $t write to log file (section ~~SECTlog) |
| 761 | \mail\ $t send a reply message (section ~~SECTmail) |
| 762 | \pipe\ $t pipe to a command (section ~~SECTpipe) |
| 763 | \save\ $t save to a file (section ~~SECTsave) |
| 764 | \testprint\ $t print while testing (section ~~SECTtestprint) |
| 765 | \vacation\ $t tailored form of \mail\ (section ~~SECTmail) |
| 766 | .endd |
| 767 | In addition, when Exim's filtering facilities are being used as a system |
| 768 | filter, the \"fail"\, \"freeze"\, and \"headers"\ commands are available. |
| 769 | However, since they are usable only by the system administrator and not by |
| 770 | ordinary users, they are described in the main Exim specification rather than |
| 771 | in this document. |
| 772 | |
| 773 | .section The add command |
| 774 | .rset SECTadd "~~chapter.~~section" |
| 775 | .display |
| 776 | add <<number>> to <<user variable>> |
| 777 | e.g. add 2 to n3 |
| 778 | .endd |
| 779 | There are 10 user variables of this type, and their values can be obtained by |
| 780 | the normal expansion syntax (for example \$n3$\) in other commands. At the |
| 781 | start of filtering, these variables all contain zero. Both arguments of the |
| 782 | \"add"\ command are expanded before use, making it possible to add variables to |
| 783 | each other. Subtraction can be obtained by adding negative numbers. |
| 784 | |
| 785 | |
| 786 | .section The deliver command |
| 787 | .rset SECTdeliver "~~chapter.~~section" |
| 788 | .display |
| 789 | deliver <<mail address>> |
| 790 | e.g. deliver "Dr Livingstone <David@@somewhere.africa.example>" |
| 791 | .endd |
| 792 | This provides a forwarding operation. The message is sent on to the given |
| 793 | address, exactly as happens if the address had appeared in a traditional |
| 794 | \(.forward)\ file. If you want to deliver the message to a number of different |
| 795 | addresses, you can use more than one \"deliver"\ command (each one may have |
| 796 | only one address). However, duplicate addresses are discarded. |
| 797 | |
| 798 | To deliver a copy of the message to your normal mailbox, your login name can be |
| 799 | given as the address. Once an address has been processed by the filtering |
| 800 | mechanism, an identical generated address will not be so processed again, so |
| 801 | doing this does not cause a loop. |
| 802 | |
| 803 | However, if you have a mail alias, you should $it{not} refer to it here. For |
| 804 | example, if the mail address \"L.Gulliver"\ is aliased to \"lg103"\ then all |
| 805 | references in Gulliver's \(.forward)\ file should be to \"lg103"\. A reference |
| 806 | to the alias will not work for messages that are addressed to that alias, |
| 807 | since, like \(.forward)\ file processing, aliasing is performed only once on an |
| 808 | address, in order to avoid looping. |
| 809 | |
| 810 | Following the new address, an optional second address, preceded by |
| 811 | \"errors@_to"\ may appear. This changes the address to which delivery errors on |
| 812 | the forwarded message will be sent. Instead of going to the message's original |
| 813 | sender, they go to this new address. For ordinary users, the only value that is |
| 814 | permitted for this address is the user whose filter file is being processed. |
| 815 | For example, the user \"lg103"\ whose mailbox is in the domain |
| 816 | \lilliput.example\ could have a filter file that contains |
| 817 | .display asis |
| 818 | deliver jon@elsewhere.example errors_to lg103@lilliput.example |
| 819 | .endd |
| 820 | Clearly, using this feature makes sense only in situations where not all |
| 821 | messages are being forwarded. In particular, bounce messages must not be |
| 822 | forwarded in this way, as this is likely to create a mail loop if something |
| 823 | goes wrong. |
| 824 | |
| 825 | |
| 826 | .section The save command |
| 827 | .rset SECTsave "~~chapter.~~section" |
| 828 | .display |
| 829 | save <<file name>> |
| 830 | e.g. save @$home/mail/bookfolder |
| 831 | .endd |
| 832 | This causes a copy of the message to be appended to the given file (that is, |
| 833 | the file is used as a mail folder). More than one \"save"\ command may appear; |
| 834 | each one causes a copy of the message to be written to its argument file, |
| 835 | provided they are different (duplicate \"save"\ commands are ignored). |
| 836 | |
| 837 | If the file name does not start with a / character, the contents of the |
| 838 | \$home$\ variable are prepended, unless it is empty. In conventional |
| 839 | configurations, this variable is normally set in a user filter to the user's |
| 840 | home directory, but the system administrator may set it to some other path. In |
| 841 | some configurations, \$home$\ may be unset, in which case a non-absolute path |
| 842 | name may be generated. Such configurations convert this to an absolute path |
| 843 | when the delivery takes place. In a system filter, \$home$\ is never set. |
| 844 | |
| 845 | The user must of course have permission to write to the file, and the writing |
| 846 | of the file takes place in a process that is running as the user, under the |
| 847 | user's primary group. Any secondary groups to which the user may belong are not |
| 848 | normally taken into account, though the system administrator can configure Exim |
| 849 | to set them up. In addition, the ability to use this command at all is |
| 850 | controlled by the system administrator -- it may be forbidden on some systems. |
| 851 | |
| 852 | An optional mode value may be given after the file name. The value for the mode |
| 853 | is interpreted as an octal number, even if it does not begin with a zero. For |
| 854 | example: |
| 855 | .display |
| 856 | save /some/folder 640 |
| 857 | .endd |
| 858 | This makes it possible for users to override the system-wide mode setting for |
| 859 | file deliveries, which is normally 600. If an existing file does not have the |
| 860 | correct mode, it is changed. |
| 861 | |
| 862 | An alternative form of delivery may be enabled on your system, in which each |
| 863 | message is delivered into a new file in a given directory. If this is the case, |
| 864 | this functionality can be requested by giving the directory name terminated by |
| 865 | a slash after the \"save"\ command, for example |
| 866 | .display |
| 867 | save separated/messages/ |
| 868 | .endd |
| 869 | There are several different formats for such deliveries; check with your system |
| 870 | administrator or local documentation to find out which (if any) are available |
| 871 | on your system. If this functionality is not enabled, the use of a path name |
| 872 | ending in a slash causes an error. |
| 873 | |
| 874 | |
| 875 | .section The pipe command |
| 876 | .rset SECTpipe "~~chapter.~~section" |
| 877 | .display |
| 878 | pipe <<command>> |
| 879 | e.g. pipe "@$home/bin/countmail @$sender@_address" |
| 880 | .endd |
| 881 | This command sets up delivery to a specified command using a pipe. Remember, |
| 882 | however, that no deliveries are done while the filter is being processed. All |
| 883 | deliveries happen later on. Therefore, the result of running the pipe is not |
| 884 | available to the filter. |
| 885 | |
| 886 | When the deliveries are done, a separate process is run, and a copy of the |
| 887 | message is passed on its standard input. The process runs as the user, under |
| 888 | the user's primary group. Any secondary groups to which the user may belong are |
| 889 | not normally taken into account, though the system administrator can configure |
| 890 | Exim to set them up. More than one \"pipe"\ command may appear; each one causes |
| 891 | a copy of the message to be written to its argument pipe, provided they are |
| 892 | different (duplicate \"pipe"\ commands are ignored). |
| 893 | |
| 894 | When the time comes to transport the message, |
| 895 | the command supplied to \"pipe"\ is split up by Exim into a command name and a |
| 896 | number of arguments. These are delimited by white space except for arguments |
| 897 | enclosed in double quotes, in which case backslash is interpreted as an escape, |
| 898 | or in single quotes, in which case no escaping is recognized. Note that as the |
| 899 | whole command is normally supplied in double quotes, a second level of quoting |
| 900 | is required for internal double quotes. For example: |
| 901 | .display asis |
| 902 | pipe "$home/myscript \"size is $message_size\"" |
| 903 | .endd |
| 904 | String expansion is performed on the separate components after the line has |
| 905 | been split up, and the command is then run directly by Exim; it is not run |
| 906 | under a shell. Therefore, substitution cannot change the number of arguments, |
| 907 | nor can quotes, backslashes or other shell metacharacters in variables cause |
| 908 | confusion. |
| 909 | |
| 910 | Documentation for some programs that are normally run via this kind of pipe |
| 911 | often suggest that the command should start with |
| 912 | .display asis |
| 913 | IFS=" " |
| 914 | .endd |
| 915 | This is a shell command, and should $it{not} be present in Exim filter files, |
| 916 | since it does not normally run the command under a shell. |
| 917 | |
| 918 | However, there is an option that the administrator can set to cause a shell to |
| 919 | be used. In this case, the entire command is expanded as a single string and |
| 920 | passed to the shell for interpretation. It is recommended that this be avoided |
| 921 | if at all possible, since it can lead to problems when inserted variables |
| 922 | contain shell metacharacters. |
| 923 | |
| 924 | The default \\PATH\\ set up for the command is determined by the system |
| 925 | administrator, usually containing at least \/usr/bin\ so that common commands |
| 926 | are available without having to specify an absolute file name. However, it is |
| 927 | possible for the system administrator to restrict the pipe facility so that the |
| 928 | command name must not contain any / characters, and must be found in one of the |
| 929 | directories in the configured \\PATH\\. It is also possible for the system |
| 930 | administrator to lock out the use of the \"pipe"\ command altogether. |
| 931 | |
| 932 | When the command is run, a number of environment variables are set up. The |
| 933 | complete list for pipe deliveries may be found in the Exim reference manual. |
| 934 | Those that may be useful for pipe deliveries from user filter files are: |
| 935 | .display |
| 936 | .tabs 20 |
| 937 | DOMAIN $t $rm{the domain of the address} |
| 938 | HOME $t $rm{your home directory} |
| 939 | LOCAL@_PART $t $rm{see below} |
| 940 | LOCAL@_PART@_PREFIX $t $rm{see below} |
| 941 | LOCAL@_PART@_SUFFIX $t $rm{see below} |
| 942 | LOGNAME $t $rm{your login name} |
| 943 | MESSAGE@_ID $t $rm{the message's unique id} |
| 944 | PATH $t $rm{the command search path} |
| 945 | RECIPIENT $t $rm{the complete recipient address} |
| 946 | SENDER $t $rm{the sender of the message} |
| 947 | SHELL $t $bf{/bin/sh} |
| 948 | USER $t $rm{see below} |
| 949 | .endd |
| 950 | \\LOCAL@_PART\\, \\LOGNAME\\, and \\USER\\ are all set to the same value, |
| 951 | namely, your login id. \\LOCAL@_PART@_PREFIX\\ and \\LOCAL@_PART@_SUFFIX\\ may |
| 952 | be set if Exim is configured to recognize prefixes or suffixes in the local |
| 953 | parts of addresses. For example, a message addressed to |
| 954 | \*pat-suf2@@domain.example*\ may cause user \*pat*\'s filter file to be run. If |
| 955 | this sets up a pipe delivery, \\LOCAL@_PART@_SUFFIX\\ is \"-suf2"\ when the |
| 956 | pipe command runs. The system administrator has to configure Exim specially for |
| 957 | this feature to be available. |
| 958 | |
| 959 | If you run a command that is a shell script, be very careful in your use of |
| 960 | data from the incoming message in the commands in your script. RFC 2822 is very |
| 961 | generous in the characters that are legally permitted to appear in mail |
| 962 | addresses, and in particular, an address may begin with a vertical bar or a |
| 963 | slash. For this reason you should always use quotes round any arguments that |
| 964 | involve data from the message, like this: |
| 965 | .display asis |
| 966 | /some/command '$SENDER' |
| 967 | .endd |
| 968 | so that inserted shell meta-characters do not cause unwanted effects. |
| 969 | |
| 970 | Remember that, as was explained earlier, the pipe command is not run at the |
| 971 | time the filter file is interpreted. The filter just defines what deliveries |
| 972 | are required for one particular addressee of a message. The deliveries |
| 973 | themselves happen later, once Exim has decided everything that needs to be done |
| 974 | for the message. |
| 975 | |
| 976 | A consequence of this is that you cannot inspect the return code from the pipe |
| 977 | command from within the filter. Nevertheless, the code returned by the command |
| 978 | is important, because Exim uses it to decide whether the delivery has succeeded |
| 979 | or failed. |
| 980 | |
| 981 | The command should return a zero completion code if all has gone well. Most |
| 982 | non-zero codes are treated by Exim as indicating a failure of the pipe. This is |
| 983 | treated as a delivery failure, causing the message to be returned to its |
| 984 | sender. However, there are some completion codes which are treated as temporary |
| 985 | errors. The message remains on Exim's spool disk, and the delivery is tried |
| 986 | again later, though it will ultimately time out if the delivery failures go on |
| 987 | too long. The completion codes to which this applies can be specified by the |
| 988 | system administrator; the default values are 73 and 75. |
| 989 | |
| 990 | The pipe command should not normally write anything to its standard output or |
| 991 | standard error file descriptors. If it does, whatever is written is normally |
| 992 | returned to the sender of the message as a delivery error, though this action |
| 993 | can be varied by the system administrator. |
| 994 | |
| 995 | |
| 996 | .section Mail commands |
| 997 | .rset SECTmail "~~chapter.~~section" |
| 998 | There are two commands which cause the creation of a new mail message, neither |
| 999 | of which count as a significant delivery unless the command is preceded by the |
| 1000 | word \"seen"\. This is a powerful facility, but it should be used with care, |
| 1001 | because of the danger of creating infinite sequences of messages. The system |
| 1002 | administrator can forbid the use of these commands altogether. |
| 1003 | |
| 1004 | To help prevent runaway message sequences, these commands have no effect when |
| 1005 | the incoming message is a delivery error message, and messages sent by this |
| 1006 | means are treated as if they were reporting delivery errors. Thus they should |
| 1007 | never themselves cause a delivery error message to be returned. The basic |
| 1008 | mail-sending command is |
| 1009 | .display |
| 1010 | mail [to <<address-list>>] |
| 1011 | [cc <<address-list>>] |
| 1012 | [bcc <<address-list>>] |
| 1013 | [from <<address>>] |
| 1014 | [reply@_to <<address>>] |
| 1015 | [subject <<text>>] |
| 1016 | [extra@_headers <<text>>] |
| 1017 | [text <<text>>] |
| 1018 | [[expand] file <<filename>>] |
| 1019 | [return message] |
| 1020 | [log <<log file name>>] |
| 1021 | [once <<note file name>>] |
| 1022 | [once@_repeat <<time interval>>] |
| 1023 | .blank |
| 1024 | e.g. mail text "Your message about @$h@_subject: has been received" |
| 1025 | .endd |
| 1026 | |
| 1027 | Each <<address-list>> can contain a number of addresses, separated by commas, |
| 1028 | in the format of a ::To:: or ::Cc:: header line. In fact, the text you supply |
| 1029 | here is copied exactly into the appropriate header line. Thus, it may contain |
| 1030 | additional information as well as email addresses. For example: |
| 1031 | .display asis |
| 1032 | mail to "Julius Caesar <jc@rome.example>, \ |
| 1033 | <ma@rome.example> (Mark A.)" |
| 1034 | .endd |
| 1035 | Similarly, the texts supplied for ::From:: and ::Reply-to:: are copied into |
| 1036 | their respective header lines. |
| 1037 | |
| 1038 | As a convenience for use in one common case, there is also a command called |
| 1039 | \vacation\. It behaves in the same way as \mail\, except that the defaults for |
| 1040 | the |
| 1041 | \"subject"\, |
| 1042 | \"file"\, \"log"\, \"once"\, and \"once@_repeat"\ options are |
| 1043 | .display |
| 1044 | subject "On vacation" |
| 1045 | expand file .vacation.msg |
| 1046 | log .vacation.log |
| 1047 | once .vacation |
| 1048 | once@_repeat 7d |
| 1049 | .endd |
| 1050 | respectively. These are the same file names and repeat period used by the |
| 1051 | traditional Unix \"vacation"\ command. The defaults can be overridden by |
| 1052 | explicit settings, but if a file name is given its contents are expanded only |
| 1053 | if explicitly requested. |
| 1054 | |
| 1055 | \**Warning**\: The \"vacation"\ command should always be used conditionally, |
| 1056 | subject to at least the \"personal"\ condition (see section ~~SECTpersonal |
| 1057 | below) so as not to send automatic replies to non-personal messages from |
| 1058 | mailing lists or elsewhere. Sending an automatic response to a mailing list or |
| 1059 | a mailing list manager is an Internet Sin. |
| 1060 | |
| 1061 | For both commands, the key/value argument pairs can appear in any order. At |
| 1062 | least one of \"text"\ or \"file"\ must appear (except with \"vacation"\); if |
| 1063 | both are present, the text string appears first in the message. If \"expand"\ |
| 1064 | precedes \"file"\, each line of the file is subject to string expansion as |
| 1065 | it is included in the message. |
| 1066 | |
| 1067 | Several lines of text can be supplied to \"text"\ by including the escape |
| 1068 | sequence `@\n' in the string where newlines are required. If the command is |
| 1069 | output during filter file testing, newlines in the text are shown as `@\n'. |
| 1070 | |
| 1071 | Note that the keyword for creating a \"Reply-To:"\ header is \reply@_to\, |
| 1072 | because Exim keywords may contain underscores, but not hyphens. If the \"from"\ |
| 1073 | keyword is present and the given address does not match the user who owns the |
| 1074 | forward file, Exim normally adds a \"Sender:"\ header to the message, |
| 1075 | though it can be configured not to do this. |
| 1076 | |
| 1077 | The \extra@_headers\ keyword allows you to add custom header lines to the |
| 1078 | message. The text supplied must be one or more syntactically valid RFC 2882 |
| 1079 | header lines. You can use `@\n' within quoted text to specify newlines between |
| 1080 | headers, and also to define continued header lines. For example: |
| 1081 | .display asis |
| 1082 | extra_headers "h1: first\nh2: second\n continued\nh3: third" |
| 1083 | .endd |
| 1084 | No newline should appear at the end of the final header line. |
| 1085 | |
| 1086 | If no \"to"\ argument appears, the message is sent to the address in the |
| 1087 | \"@$reply@_address"\ variable (see section ~~SECTfilterstringexpansion above). |
| 1088 | An \"In-Reply-To:"\ header is automatically included in the created message, |
| 1089 | giving a reference to the message identification of the incoming message. |
| 1090 | |
| 1091 | If \"return message"\ is specified, the incoming message that caused the filter |
| 1092 | file to be run is added to the end of the message, subject to a maximum size |
| 1093 | limitation. |
| 1094 | |
| 1095 | If a log file is specified, a line is added to it for each message sent. |
| 1096 | |
| 1097 | If a \"once"\ file is specified, it is used to hold a database for remembering |
| 1098 | who has received a message, and no more than one message is ever sent to any |
| 1099 | particular address, unless \"once@_repeat"\ is set. This specifies a time |
| 1100 | interval after which another copy of the message is sent. The interval is |
| 1101 | specified as a sequence of numbers, each followed by the initial letter of one |
| 1102 | of `seconds', `minutes', `hours', `days', or `weeks'. For example, |
| 1103 | .display asis |
| 1104 | once_repeat 5d4h |
| 1105 | .endd |
| 1106 | causes a new message to be sent if 5 days and 4 hours have elapsed since the |
| 1107 | last one was sent. There must be no white space in a time interval. |
| 1108 | |
| 1109 | Commonly, the file name specified for \"once"\ is used as the base name for |
| 1110 | direct-access (DBM) file operations. There are a number of different DBM |
| 1111 | libraries in existence. Some operating systems provide one as a default, but |
| 1112 | even in this case a different one may have been used when building Exim. With |
| 1113 | some DBM libraries, specifying \"once"\ results in two files being created, |
| 1114 | with the suffixes \".dir"\ and \".pag"\ being added to the given name. With |
| 1115 | some others a single file with the suffix \".db"\ is used, or the name is used |
| 1116 | unchanged. |
| 1117 | |
| 1118 | Using a DBM file for implementing the \"once"\ feature means that the file |
| 1119 | grows as large as necessary. This is not usually a problem, but some system |
| 1120 | administrators want to put a limit on it. The facility can be configured not to |
| 1121 | use a DBM file, but instead, to use a regular file with a maximum size. The |
| 1122 | data in such a file is searched sequentially, and if the file fills up, the |
| 1123 | oldest entry is deleted to make way for a new one. This means that some |
| 1124 | correspondents may receive a second copy of the message after an unpredictable |
| 1125 | interval. Consult your local information to see if your system is configured |
| 1126 | this way. |
| 1127 | |
| 1128 | More than one \"mail"\ or \"vacation"\ command may be obeyed in a single filter |
| 1129 | run; they are all honoured, even when they are to the same recipient. |
| 1130 | |
| 1131 | |
| 1132 | .section Logging commands |
| 1133 | .rset SECTlog "~~chapter.~~section" |
| 1134 | A log can be kept of actions taken by a filter file. This facility is normally |
| 1135 | available in conventional configurations, but there are some situations where |
| 1136 | it might not be. Also, the system administrator may choose to disable it. Check |
| 1137 | your local information if in doubt. |
| 1138 | |
| 1139 | Logging takes place while the filter file is being interpreted. It does not |
| 1140 | queue up for later like the delivery commands. The reason for this is so that a |
| 1141 | log file need be opened only once for several write operations. There are two |
| 1142 | commands, neither of which constitutes a significant delivery. The first |
| 1143 | defines a file to which logging output is subsequently written: |
| 1144 | .display |
| 1145 | logfile <<file name>> |
| 1146 | e.g. logfile @$home/filter.log |
| 1147 | .endd |
| 1148 | The file name must be fully qualified. You can use \$home$\, as in this |
| 1149 | example, to refer to your home directory. The file name may optionally be |
| 1150 | followed by a mode for the file, which is used if the file has to be created. |
| 1151 | For example, |
| 1152 | .display |
| 1153 | logfile @$home/filter.log 0644 |
| 1154 | .endd |
| 1155 | The number is interpreted as octal, even if it does not begin with a zero. |
| 1156 | The default for the mode is 600. It is suggested that the \"logfile"\ command |
| 1157 | normally appear as the first command in a filter file. Once \"logfile"\ has |
| 1158 | been obeyed, the \"logwrite"\ command can be used to write to the log file: |
| 1159 | .display |
| 1160 | logwrite "<<some text string>>" |
| 1161 | e.g. logwrite "@$tod@_log @$message@_id processed" |
| 1162 | .endd |
| 1163 | It is possible to have more than one \"logfile"\ command, to specify writing to |
| 1164 | different log files in different circumstances. Writing takes place at the end |
| 1165 | of the file, and a newline character is added to the end of each string if |
| 1166 | there isn't one already there. Newlines can be put in the middle of the string |
| 1167 | by using the `@\n' escape sequence. Lines from simultaneous deliveries may get |
| 1168 | interleaved in the file, as there is no interlocking, so you should plan your |
| 1169 | logging with this in mind. However, data should not get lost. |
| 1170 | |
| 1171 | |
| 1172 | .section The finish command |
| 1173 | .rset SECTfinish "~~chapter.~~section" |
| 1174 | The command \"finish"\, which has no arguments, causes Exim to stop |
| 1175 | interpreting the filter file. This is not a significant action unless preceded |
| 1176 | by \"seen"\. A filter file containing only \"seen finish"\ is a black hole. |
| 1177 | |
| 1178 | .section The testprint command |
| 1179 | .rset SECTtestprint "~~chapter.~~section" |
| 1180 | It is sometimes helpful to be able to print out the values of variables when |
| 1181 | testing filter files. The command |
| 1182 | .display |
| 1183 | testprint <<text>> |
| 1184 | e.g. testprint "home=@$home reply@_address=@$reply@_address" |
| 1185 | .endd |
| 1186 | does nothing when mail is being delivered. However, when the filtering code is |
| 1187 | being tested by means of the \-bf-\ option (see section ~~SECTtesting above), |
| 1188 | the value of the string is written to the standard output. |
| 1189 | |
| 1190 | .section The fail command |
| 1191 | .rset SECTfail "~~chapter.~~section" |
| 1192 | When Exim's filtering facilities are being used as a system filter, the |
| 1193 | \"fail"\ command is available, to force delivery failure. Because this command |
| 1194 | is normally usable only by the system administrator, and not enabled for use by |
| 1195 | ordinary users, it is described in more detail in the main Exim specification |
| 1196 | rather than in this document. |
| 1197 | |
| 1198 | .section The freeze command |
| 1199 | .rset SECTfreeze "~~chapter.~~section" |
| 1200 | When Exim's filtering facilities are being used as a system filter, the |
| 1201 | \"freeze"\ command is available, to freeze a message on the queue. Because this |
| 1202 | command is normally usable only by the system administrator, and not enabled |
| 1203 | for use by ordinary users, it is described in more detail in the main Exim |
| 1204 | specification rather than in this document. |
| 1205 | |
| 1206 | |
| 1207 | .section The headers command |
| 1208 | .rset SECTheaders "~~chapter.~~section" |
| 1209 | The \"headers"\ command can be used to change the target character set which is |
| 1210 | used when translating the contents of encoded header lines for insertion by the |
| 1211 | \"@$header@_"\ mechanism (see section ~~SECTheadervariables above). The default |
| 1212 | can be set in the Exim configuration; if not specified, ISO-8859-1 is used. The |
| 1213 | only currently supported format for the \"headers"\ command is as in this |
| 1214 | example: |
| 1215 | .display asis |
| 1216 | headers charset "UTF-8" |
| 1217 | .endd |
| 1218 | That is, \"headers"\ is followed by the word \"charset"\ and then the name of a |
| 1219 | character set. This particular example would be useful if you wanted to compare |
| 1220 | the contents of a header to a UTF-8 string. |
| 1221 | |
| 1222 | |
| 1223 | .section Obeying commands conditionally |
| 1224 | .rset SECTif "~~chapter.~~section" |
| 1225 | Most of the power of filtering comes from the ability to test conditions and |
| 1226 | obey different commands depending on the outcome. The \"if"\ command is used to |
| 1227 | specify conditional execution, and its general form is |
| 1228 | .display |
| 1229 | if <<condition>> |
| 1230 | then <<commands>> |
| 1231 | elif <<condition>> |
| 1232 | then <<commands>> |
| 1233 | else <<commands>> |
| 1234 | endif |
| 1235 | .endd |
| 1236 | There may be any number of \"elif"\ and \"then"\ sections (including none) and |
| 1237 | the \"else"\ section is also optional. Any number of commands, including nested |
| 1238 | \"if"\ commands, may appear in any of the <<commands>> sections. |
| 1239 | |
| 1240 | Conditions can be combined by using the words \"and"\ and \"or"\, and round |
| 1241 | brackets (parentheses) can be used to specify how several conditions are to |
| 1242 | combine. Without brackets, \"and"\ is more binding than \"or"\. |
| 1243 | For example, |
| 1244 | .display asis |
| 1245 | if |
| 1246 | $h_subject: contains "Make money" or |
| 1247 | $h_precedence: is "junk" or |
| 1248 | ($h_sender: matches ^\\d{8}@ and not personal) or |
| 1249 | $message_body contains "this is spam" |
| 1250 | then |
| 1251 | seen finish |
| 1252 | endif |
| 1253 | .endd |
| 1254 | A condition can be preceded by \"not"\ to negate it, and there are also some |
| 1255 | negative forms of condition that are more English-like. |
| 1256 | |
| 1257 | |
| 1258 | |
| 1259 | .section String testing conditions |
| 1260 | There are a number of conditions that operate on text strings, using the words |
| 1261 | `begins', `ends', `is', `contains' and `matches'. |
| 1262 | |
| 1263 | Note that if you want to apply the same test to more than one header line, you |
| 1264 | can easily concatenate them into a single string for testing, as in this |
| 1265 | example: |
| 1266 | .display asis |
| 1267 | if "$h_to:, $h_cc:" contains me@domain.example then ... |
| 1268 | .endd |
| 1269 | |
| 1270 | If any of the condition names are written in lower case, the testing of letters |
| 1271 | is done without regard to case; if they are written in upper case (for example, |
| 1272 | `CONTAINS') then the case of letters is significant. |
| 1273 | .display |
| 1274 | <<text1>> begins <<text2>> |
| 1275 | <<text1>> does not begin <<text2>> |
| 1276 | e.g. @$header@_from: begins "Friend@@" |
| 1277 | .endd |
| 1278 | A `begins' test checks for the presence of the second string at the start of |
| 1279 | the first, both strings having been expanded. |
| 1280 | .display |
| 1281 | <<text1>> ends <<text2>> |
| 1282 | <<text1>> does not end <<text2>> |
| 1283 | e.g. @$header@_from: ends "@public.com.example" |
| 1284 | .endd |
| 1285 | An `ends' test checks for the presence of the second string at the end of |
| 1286 | the first, both strings having been expanded. |
| 1287 | .display |
| 1288 | <<text1>> is <<text2>> |
| 1289 | <<text1>> is not <<text2>> |
| 1290 | e.g. @$local@_part@_suffix is "-foo" |
| 1291 | .endd |
| 1292 | An `is' test does an exact match between the strings, having first expanded |
| 1293 | both strings. |
| 1294 | .display |
| 1295 | <<text1>> contains <<text2>> |
| 1296 | <<text1>> does not contain <<text2>> |
| 1297 | e.g. @$header@_subject: contains "evolution" |
| 1298 | .endd |
| 1299 | A `contains' test does a partial string match, having expanded both strings. |
| 1300 | .display |
| 1301 | <<text1>> matches <<text2>> |
| 1302 | <<text1>> does not match <<text2>> |
| 1303 | e.g. @$sender@_address matches "(bill|john)@@" |
| 1304 | .endd |
| 1305 | For a `matches' test, after expansion of both strings, the second one is |
| 1306 | interpreted as a regular expression. Exim uses the PCRE regular expression |
| 1307 | library, which provides regular expressions that are compatible with Perl. |
| 1308 | |
| 1309 | .em |
| 1310 | The match succeeds if the regular expression matches any part of the first |
| 1311 | string. If you want a regular expression to match only at the start or end of |
| 1312 | the subject string, you must encode that requirement explicitly, using the @^ |
| 1313 | or @$ metacharacters. The above example, which is not so constrained, matches |
| 1314 | all these addresses: |
| 1315 | .display asis |
| 1316 | bill@test.example |
| 1317 | john@some.example |
| 1318 | spoonbill@example.com |
| 1319 | littlejohn@example.com |
| 1320 | .endd |
| 1321 | To match only the first two, you could use this: |
| 1322 | .display asis |
| 1323 | if $sender_address matches "^(bill|john)@" then ... |
| 1324 | .endd |
| 1325 | .nem |
| 1326 | |
| 1327 | Care must be taken if you need a backslash in a regular expression, because |
| 1328 | backslashes are interpreted as escape characters both by the string expansion |
| 1329 | code and by Exim's normal processing of strings in quotes. For example, if you |
| 1330 | want to test the sender address for a domain ending in \".com"\ the regular |
| 1331 | expression is |
| 1332 | .display asis |
| 1333 | \.com$ |
| 1334 | .endd |
| 1335 | The backslash and dollar sign in that expression have to be escaped when used |
| 1336 | in a filter command, as otherwise they would be interpreted by the expansion |
| 1337 | code. Thus what you actually write is |
| 1338 | .display asis |
| 1339 | if $sender_address matches \\.com\$ |
| 1340 | .endd |
| 1341 | An alternative way of handling this is to make use of the \"@\N"\ expansion |
| 1342 | flag for suppressing expansion: |
| 1343 | .display asis |
| 1344 | if $sender_address matches \N\.com$\N |
| 1345 | .endd |
| 1346 | Everything between the two occurrences of \"@\N"\ is copied without change by |
| 1347 | the string expander (and in fact you do not need the final one, because it is |
| 1348 | at the end of the string). |
| 1349 | |
| 1350 | If the regular expression is given in quotes (mandatory only if it contains |
| 1351 | white space) you have to write either |
| 1352 | .display asis |
| 1353 | if $sender_address matches "\\\\.com\\$" |
| 1354 | .endd |
| 1355 | or |
| 1356 | .display asis |
| 1357 | if $sender_address matches "\\N\\.com$\\N" |
| 1358 | .endd |
| 1359 | |
| 1360 | |
| 1361 | If the regular expression contains bracketed sub-expressions, numeric |
| 1362 | variable substitutions such as \$1$\ can be used in the subsequent actions |
| 1363 | after a successful match. If the match fails, the values of the numeric |
| 1364 | variables remain unchanged. Previous values are not restored after \"endif"\ -- |
| 1365 | in other words, only one set of values is ever available. If the condition |
| 1366 | contains several sub-conditions connected by \"and"\ or \"or"\, it is the |
| 1367 | strings extracted from the last successful match that are available in |
| 1368 | subsequent actions. Numeric variables from any one sub-condition are also |
| 1369 | available for use in subsequent sub-conditions, since string expansion of a |
| 1370 | condition occurs just before it is tested. |
| 1371 | |
| 1372 | .section Numeric testing conditions |
| 1373 | The following conditions are available for performing numerical tests: |
| 1374 | .display |
| 1375 | <<number1>> is above <<number2>> |
| 1376 | <<number1>> is not above <<number2>> |
| 1377 | <<number1>> is below <<number2>> |
| 1378 | <<number1>> is not below <<number2>> |
| 1379 | e.g. @$message@_size is not above 10k |
| 1380 | .endd |
| 1381 | The <<number>> arguments must expand to strings of digits, optionally followed |
| 1382 | by one of the letters K or M (upper case or lower case) which cause |
| 1383 | multiplication by 1024 and 1024x1024 respectively. |
| 1384 | |
| 1385 | .section Testing for significant deliveries |
| 1386 | Whether or not any previously obeyed filter commands have resulted in a |
| 1387 | significant delivery can be tested by the condition \"delivered"\, for example: |
| 1388 | .display asis |
| 1389 | if not delivered then save mail/anomalous endif |
| 1390 | .endd |
| 1391 | |
| 1392 | .section Testing for error messages |
| 1393 | The condition \"error@_message"\ is true if the incoming message is a mail |
| 1394 | delivery error message (bounce message). Putting the command |
| 1395 | .display asis |
| 1396 | if error_message then finish endif |
| 1397 | .endd |
| 1398 | at the head of your filter file is a useful insurance against things going |
| 1399 | wrong in such a way that you cannot receive delivery error reports, and is |
| 1400 | highly recommended. Note that \"error@_message"\ is a condition, not an |
| 1401 | expansion variable, and therefore is not preceded by \@$\. |
| 1402 | |
| 1403 | .section Testing for personal mail |
| 1404 | .rset SECTpersonal "~~chapter.~~section" |
| 1405 | A common requirement is to distinguish between incoming personal mail and mail |
| 1406 | from a mailing list, |
| 1407 | or from a robot or other automatic process (for example, a bounce message). |
| 1408 | In particular, this test is normally required for so-called `vacation |
| 1409 | messages'. The condition |
| 1410 | .display |
| 1411 | personal |
| 1412 | .endd |
| 1413 | is a shorthand for |
| 1414 | .display |
| 1415 | not error@_message and |
| 1416 | @$header@_to: contains "@$local@_part@@@$domain" and |
| 1417 | @$header@_from: does not contain "@$local@_part@@@$domain" and |
| 1418 | @$header@_from: does not contain "server@@" and |
| 1419 | @$header@_from: does not contain "daemon@@" and |
| 1420 | @$header@_from: does not contain "root@@" and |
| 1421 | @$header@_auto-submitted: does not contain "auto-" and |
| 1422 | @$header@_subject: does not contain "circular" and |
| 1423 | @$header@_precedence: does not contain "bulk" and |
| 1424 | @$header@_precedence: does not contain "list" and |
| 1425 | @$header@_precedence: does not contain "junk" |
| 1426 | .endd |
| 1427 | The variable \$local@_part$\ contains the local part of the mail address of |
| 1428 | the user whose filter file is being run -- it is normally your login id. The |
| 1429 | \$domain$\ variable contains the mail domain. This condition tests for the |
| 1430 | appearance of the current user in the \"To:"\ header, checks that the sender is |
| 1431 | not the current user or one of a number of common daemons, and checks the |
| 1432 | content of the \"Subject:"\ and \"Precedence:"\ headers. |
| 1433 | |
| 1434 | If prefixes or suffixes are in use for local parts -- something which depends |
| 1435 | on the configuration of Exim (see section ~~SECTmbox below) -- the first two |
| 1436 | tests above are also done with |
| 1437 | .display asis |
| 1438 | $local_part_prefix$local_part$local_part_suffix |
| 1439 | .endd |
| 1440 | instead of just \$local@_part$\. If the system is configured to rewrite local |
| 1441 | parts of mail addresses, for example, to rewrite `dag46' as `Dirk.Gently', |
| 1442 | the rewritten form of the address is also used in the tests. |
| 1443 | |
| 1444 | This example shows the use of \"personal"\ in a filter file that is sending out |
| 1445 | vacation messages: |
| 1446 | .display asis |
| 1447 | if personal then |
| 1448 | mail |
| 1449 | to $reply_address |
| 1450 | subject "Re: $h_subject:" |
| 1451 | file $home/vacation/message |
| 1452 | once $home/vacation/once |
| 1453 | once_repeat 10d |
| 1454 | endif |
| 1455 | .endd |
| 1456 | |
| 1457 | It is quite common for people who have mail accounts on a number of different |
| 1458 | systems to forward all their mail to one system, and in this case a check for |
| 1459 | personal mail should test all their various mail addresses. To allow for this, |
| 1460 | the \"personal"\ condition keyword can be followed by |
| 1461 | .display |
| 1462 | alias <<address>> |
| 1463 | .endd |
| 1464 | any number of times, for example |
| 1465 | .display asis |
| 1466 | if personal alias smith@else.where.example |
| 1467 | alias jones@other.place.example |
| 1468 | then ... |
| 1469 | .endd |
| 1470 | This causes messages containing the alias addresses in any places where the |
| 1471 | local address is tested to be treated as personal. |
| 1472 | |
| 1473 | .section Testing delivery status |
| 1474 | There are two conditions which are intended mainly for use in system filter |
| 1475 | files, but which are available in users' filter files as well. The condition |
| 1476 | \"first@_delivery"\ is true if this is the first attempt to deliver the |
| 1477 | message, and false otherwise. |
| 1478 | .em |
| 1479 | This indicator is not reset until the first delivery process successfully |
| 1480 | terminates; if there is a crash or a power failure (for example), the next |
| 1481 | delivery attempt is also a `first delivery'. |
| 1482 | .nem |
| 1483 | |
| 1484 | In a user filter file it will be false only if |
| 1485 | there was previously an error in the filter, or if a delivery for the user |
| 1486 | failed owing to, for example, a quota error, or forwarding to a remote |
| 1487 | address that was deferred for some reason. |
| 1488 | |
| 1489 | The condition \"manually@_thawed"\ is true only if the message was `frozen' for |
| 1490 | some reason, and was subsequently released by the system administrator. It is |
| 1491 | unlikely to be of use in users' filter files. |
| 1492 | |
| 1493 | .section Testing a list of addresses |
| 1494 | There is a facility for looping through a list of addresses and applying a |
| 1495 | condition to each of them. It takes the form |
| 1496 | .display |
| 1497 | foranyaddress <<string>> (<<condition>>) |
| 1498 | .endd |
| 1499 | where <<string>> is interpreted as a list of RFC 2822 addresses, as in a |
| 1500 | typical header line, and <<condition>> is any valid filter condition or |
| 1501 | combination of conditions. The `group' syntax that is defined for certain |
| 1502 | header lines that contain addresses is supported. |
| 1503 | |
| 1504 | The parentheses surrounding the condition are mandatory, to delimit it from |
| 1505 | possible further sub-conditions of the enclosing \"if"\ command. Within the |
| 1506 | condition, the expansion variable \$thisaddress$\ is set to the non-comment |
| 1507 | portion of each of the addresses in the string in turn. For example, if the |
| 1508 | string is |
| 1509 | .display asis |
| 1510 | B.Simpson <bart@sfld.example>, lisa@sfld.example (his sister) |
| 1511 | .endd |
| 1512 | then \$thisaddress$\ would take on the values \"bart@@sfld.example"\ and |
| 1513 | \"lisa@@sfld.example"\ in turn. |
| 1514 | |
| 1515 | If there are no valid addresses in the list, the whole condition is false. If |
| 1516 | the internal condition is true for any one address, the overall condition is |
| 1517 | true and the loop ends. If the internal condition is false for all addresses in |
| 1518 | the list, the overall condition is false. This example tests for the presence |
| 1519 | of an eight-digit local part in any address in a \To:\ header: |
| 1520 | .display asis |
| 1521 | if foranyaddress $h_to: ( $thisaddress matches ^\\d{8}@ ) then ... |
| 1522 | .endd |
| 1523 | When the overall condition is true, the value of \$thisaddress$\ in the |
| 1524 | commands that follow \"then"\ is the last value it took on inside the loop. At |
| 1525 | the end of the \"if"\ command, the value of \$thisaddress$\ is reset to what it |
| 1526 | was before. It is best to avoid the use of multiple occurrences of |
| 1527 | \"foranyaddress"\, nested or otherwise, in a single \"if"\ command, if the |
| 1528 | value of \$thisaddress$\ is to be used afterwards, because it isn't always |
| 1529 | clear what the value will be. Nested \"if"\ commands should be used instead. |
| 1530 | |
| 1531 | Header lines can be joined together if a check is to be applied to more than |
| 1532 | one of them. For example: |
| 1533 | .display asis |
| 1534 | if foranyaddress $h_to:,$h_cc: .... |
| 1535 | .endd |
| 1536 | scans through the addresses in both the \To:\ and the \Cc:\ headers. |
| 1537 | |
| 1538 | .section Multiple personal mailboxes |
| 1539 | .rset SECTmbox "~~chapter.~~section" |
| 1540 | The system administrator can configure Exim so that users can set up variants |
| 1541 | on their email addresses and handle them separately. Consult your system |
| 1542 | administrator or local documentation to see if this facility is enabled on your |
| 1543 | system, and if so, what the details are. |
| 1544 | |
| 1545 | The facility involves the use of a prefix or a suffix on an email address. For |
| 1546 | example, all mail addressed to \lg103-<<something>>\ would be the property of |
| 1547 | user \lg103\, who could determine how it was to be handled, depending on the |
| 1548 | value of <<something>>. |
| 1549 | |
| 1550 | There are two possible ways in which this can be set up. The first possibility |
| 1551 | is the use of multiple \(.forward)\ files. In this case, mail to \lg103-foo\, |
| 1552 | for example, is handled by looking for a file called \.forward-foo\ in |
| 1553 | \lg103's\ home directory. If such a file does not exist, delivery fails and the |
| 1554 | message is returned to its sender. |
| 1555 | |
| 1556 | The alternative approach is to pass all messages through a single \(.forward)\ |
| 1557 | file, which must be a filter file in order to distinguish between the different |
| 1558 | cases by referencing the variables \$local@_part@_prefix$\ or |
| 1559 | \$local@_part@_suffix$\, as in the final example in section ~~SECTex below. If |
| 1560 | the filter file does not handle a prefixed or suffixed address, delivery fails |
| 1561 | and the message is returned to its sender. |
| 1562 | |
| 1563 | It is possible to configure Exim to support both schemes at once. In this case, |
| 1564 | a specific \.forward-foo\ file is first sought; if it is not found, the basic |
| 1565 | \(.forward)\ file is used. |
| 1566 | |
| 1567 | The \"personal"\ test (see section ~~SECTpersonal) includes prefixes and |
| 1568 | suffixes in its checking. |
| 1569 | |
| 1570 | |
| 1571 | .section Ignoring delivery errors |
| 1572 | As was explained above, filtering just sets up addresses for delivery -- no |
| 1573 | deliveries are actually done while a filter file is active. If any of the |
| 1574 | generated addresses subsequently suffers a delivery failure, an error message |
| 1575 | is generated in the normal way. However, if the filter command which sets up a |
| 1576 | delivery is preceded by the word \"noerror"\, errors for that delivery, |
| 1577 | $it{and any deliveries consequent on it} (that is, from alias, forwarding, or |
| 1578 | filter files it invokes) are ignored. |
| 1579 | |
| 1580 | |
| 1581 | .section Examples of Exim filter commands |
| 1582 | .rset SECTex "~~chapter.~~section" |
| 1583 | Simple forwarding: |
| 1584 | .display asis |
| 1585 | # Exim filter |
| 1586 | deliver baggins@rivendell.middle-earth.example |
| 1587 | .endd |
| 1588 | Vacation handling using traditional means, assuming that the \.vacation.msg\ |
| 1589 | and other files have been set up in your home directory: |
| 1590 | .display asis |
| 1591 | # Exim filter |
| 1592 | unseen pipe "/usr/ucb/vacation \"$local_part\"" |
| 1593 | .endd |
| 1594 | Vacation handling inside Exim, having first created a file called |
| 1595 | \.vacation.msg\ in your home directory: |
| 1596 | .display asis |
| 1597 | # Exim filter |
| 1598 | if personal then vacation endif |
| 1599 | .endd |
| 1600 | File some messages by subject: |
| 1601 | .display asis |
| 1602 | # Exim filter |
| 1603 | if $header_subject: contains "empire" or |
| 1604 | $header_subject: contains "foundation" |
| 1605 | then |
| 1606 | save $home/mail/f+e |
| 1607 | endif |
| 1608 | .endd |
| 1609 | Save all non-urgent messages by weekday: |
| 1610 | .display asis |
| 1611 | # Exim filter |
| 1612 | if $header_subject: does not contain "urgent" and |
| 1613 | $tod_full matches "^(...)," |
| 1614 | then |
| 1615 | save $home/mail/$1 |
| 1616 | endif |
| 1617 | .endd |
| 1618 | Throw away all mail from one site, except from postmaster: |
| 1619 | .display asis |
| 1620 | # Exim filter |
| 1621 | if $reply_address contains "@spam.site.example" and |
| 1622 | $reply_address does not contain "postmaster@" |
| 1623 | then |
| 1624 | seen finish |
| 1625 | endif |
| 1626 | .endd |
| 1627 | .if ~~sgcal |
| 1628 | .if ~~sys.leftonpage < 6ld |
| 1629 | .newpage |
| 1630 | .fi |
| 1631 | .fi |
| 1632 | Handle multiple personal mailboxes |
| 1633 | .display asis |
| 1634 | # Exim filter |
| 1635 | if $local_part_suffix is "-foo" |
| 1636 | then |
| 1637 | save $home/mail/foo |
| 1638 | elif $local_part_suffix is "-bar" |
| 1639 | then |
| 1640 | save $home/mail/bar |
| 1641 | endif |
| 1642 | .endd |
| 1643 | |
| 1644 | . End of filter |