1MAILDROP(1) Double Precision, Inc. MAILDROP(1)
2
6 maildrop - mail delivery filter/agent
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9 maildrop [option...] [-d user] [arg...]
10 maildrop [option...] [filename] [arg...]
12
14 maildrop is a replacement local mail delivery agent that includes a
15 mail filtering language. The system administrator can either replace
16 the existing mail delivery agent with maildrop, or users may run
17 maildrop using the 'forward to program' mechanism of the existing mail
18 delivery agent.
19 maildrop first reads the E-mail message on standard input. Trailing
21 carriage return characters are automatically stripped. An E-mail
22 message consists of header lines, followed by a blank line, followed by
23 the contents of the message. The message may contain an mbox-style
24 From_ line before the first header line. If the message does not
25 contain a From_ line, maildrop will create one (if needed).
26 If the file /etc/maildroprc exists, mail delivery or mail filtering
28 instructions are read from that file. maildrop's delivery/filtering
29 instructions may direct maildrop to save the message in specific
30 mailbox, discard it, return it to sender, or forward it to a different
31 E-mail address.
32 If /etc/maildroprc does not exist, or its mail delivery instructions do
34 not completely dispose of this message, maildrop then reads the mail
35 delivery instructions from $HOME/.mailfilter. If it doesn't exist, or
36 its mail delivery instructions do not completely dispose of the
37 message, maildrop then saves the E-mail message in the default mailbox.
38 maildrop knows how to deliver mail to an standard mailbox files; it
40 also knows how to deliver to maildirs. A maildir is a directory-based
41 mail format used by the Courier[1] and Qmail[2] mail servers. Many
42 other mail servers also know how to read maildirs. When delivering to
43 mailbox files, maildrop will lock the mailbox for the duration of the
44 delivery.
45 At least one mail program writes an empty line before a From_ header
47 when saving a message into a file. maildrop ignores empty lines at the
48 beginning of messages. Therefore, maildrop requires that every message
49 must have at least one header line.
50 This is the general mail delivery behavior. There are minor differences
52 in behavior depending on maildrop delivery mode, which is determined
53 based on how maildrop was started. maildrop uses three different
54 primary operating modes:
55 Manual mode
57 A file containing filtering instructions - filename is specified as
58 an argument to the maildrop command. maildrop reads this filename
59 (after /etc/maildroprc) and follows the instructions in it. Unless
60 the message is explicitly forwarded, bounced, deleted, or delivered
61 to a specific mailbox, it will be delivered to the user's system
62 mailbox.
63 Delivery mode
65 maildrop is the mail server's mail delivery agent. maildrop runs
67 in delivery mode when no filename is specified on the command line.
68 maildrop changes the current directory to the user's home
69 directory, then reads /etc/maildroprc, then $HOME/.mailfilter.
70 Embedded mode
72 maildrop functions as a part of another application. The embedded
74 mode is used by the Courier[1] mail server to integrate mail
75 filtering directly into the process of receiving mail from a remote
76 mail relay, thus rejecting unwanted mail before it is even accepted
77 for local mail delivery. Embedded mode is used when either the -m,
78 or the -M, option is specified, and is described below. See below
79 for a more extensive description of the embedded mode.
80
82 It is safe to install maildrop as a root setuid program. Courier[1]
83 installs maildrop as a root setuid program by default, in order to be
84 able to use maildrop in embedded mode. If root runs maildrop (or it is
85 setuided to root) the -d option may be used to specify the message's
86 recipient. maildrop immediately resets its userid to the one specified
87 by the -d option. The user's $HOME/.mailfilter is read (if it exists),
88 and the message is delivered to the indicated user.
89 The system administrator can configure maildrop to restrict the -d
91 option for everyone except the mail system itself.
92 If in delivery mode the user's home directory has the sticky bit set,
94 maildrop immediately terminates with an exit code of EX_TEMPFAIL,
95 without doing anything. Mail servers interpret the EX_TEMPFAIL exit
96 code as a request to reschedule the message for another delivery
97 attempt later. Setting the sticky bit allows $HOME/.mailfilter to be
98 edited while temporarily holding all incoming mail.
99 maildrop also terminates with EX_TEMPFAIL if the user's home directory
101 has world write permissions.
102 maildrop immediately terminates with EX_TEMPFAIL if the filename is not
104 owned by the user, or if it has any group or world permissions. This
105 includes read permissions. The permissions on $HOME/.mailfilter may
106 only include read and write privileges to the user.
107 When using the special embedded mode (see below) maildrop immediately
109 terminates with the exit code set to EX_TEMPFAIL if $HOME/.mailfilters
110 is not owned by the user, or if it has any group or world permissions.
111
113 maildrop is heavily optimized and tries to use as little resources as
114 possible. maildrop reads smalle messages into memory, then filters
115 and/or delivers the message directly from memory. For larger messages,
116 maildrop accesses the message directly from the file. If the standard
117 input is not a file, maildrop writes the message to a temporary file,
118 then accesses the message from the temporary file. The temporary file
119 is automatically removed when the message is delivered.
120
122 -a
123 Makes the Courier Authentication Library usage mandatory, i.e.
124 maildrop will throw a temporary error code if the call to the
125 authlib mechanism fails for some reason, such as authdaemon being
126 inaccessible.
127 Note
129 This setting may already be the default, depending on maildrop's
130 configuration.
131 -A "Header: value"
133 Adds an additional header to the message. Specifying -A "Foo: Bar"
134 effectively adds this header to the message being delivered.
135 The mail transport agent usually adds additional headers when
137 delivering a message to a local mailbox. The way it's usually done
138 is by the mail transport agent sending the message using a pipe to
139 the local delivery agent - such as maildrop - and adding some
140 additional headers in the process. Because maildrop receives the
141 message from a pipe, maildrop must either save the message in
142 memory or write the message into a temporary file.
143 The -A option enables the file containing the message to be
145 provided to maildrop directly, as standard input, and the
146 additional headers specified on the command line. Because the
147 standard input is a file, maildrop will not need a temporary file.
148 Multiple -A options may be specified.
149 -d user
151 Run maildrop in delivery mode for this user ID.
152 The system administrator may optionally restrict the -d option to
154 be available to the mail system only, so it may not be available to
155 you. In all cases, the -d option is allowed if user is the same
156 user who is running maildrop. Also, for the -d option to work at
157 all, maildrop must be executed by root, or maildrop must be a
158 root-owned program with the setuid bit set. Absence of a filename
159 on maildrop's command line implies the -d option for the user
160 running maildrop.
161 If -d is not specified, the first argument following all the
163 options is a name of the file containing filtering instructions.
164 The remaining arguments, if any, are assigned to the variables $1,
165 $2, and so on (see "Environment"[3] and "Variable
166 substitution"[4]).
167 -f address
169 Sets the FROM variable (message envelope sender) to address. The
170 system administrator may optionally disable the -f option for
171 users, so it may not be available to you.
172 -m
174 Run maildrop in embedded mode. It's possible to use both the -m,
175 and the -d options, but it doesn't make much sense to do so. Even
176 if you really wanted to run your message through someone else's
177 .mailfilter, that .mailfilter probably has at least one instruction
178 which is not allowed in the embedded mode.
179 The filename argument to maildrop should be specified. filename is
181 a file that includes filtering instructions to be processed in
182 embedded mode. The -m option is used for debugging filter files
183 which are later placed in $HOME/.mailfilters, and used with the -M
184 option.
185 -M filterfile
187 Run maildrop in a special embedded mode. The -d option is implied
188 when -M is used, and if absent it defaults to the userid running
189 maildrop.
190 All the requirements for the -d option apply. maildrop must either
192 be executed by root, or the maildrop program must be owned by root
193 with the setuid bit set. maildrop immediately gives up root
194 privileges by changing its user ID to the one specified by -d, then
195 reads $HOME/.mailfilters/filterfile. For security reasons the name
196 of the file may not begin with a slash or include periods.
197 maildrop is very paranoid: both $HOME/.mailfilters, and
198 $HOME/.mailfilters/filterfile must be owned by the user, and may
199 not have any group or world permissions.
200 The -M option allows for some friendly cooperation between the user
202 running the application, and the user who provides a filter for the
203 embedded mode. The user running the application can use someone
204 else's canned filter and be assured that the filter is not going to
205 run amok and start sending mail or create files all over the place.
206 The user who provides the filter can be assured that the
207 environment variables are clean, and that there are no surprises.
208 maildrop supports the concept of "default" filter files. If the
211 file specified by the -M option cannot be found in
212 $HOME/.mailfilters, maildrop will try to open
213 $HOME/.mailfilters/filterfileprefix-default. filterfileprefix is
214 the initial part of filterfile up until the last '-' character in
215 filterfile.
216 If $HOME/.mailfilters/filterfileprefix-default does not exist, and
218 there are any other dashes left in filterfileprefix, maildrop
219 removes the last dash and everything following it, then tries
220 again.
221 As a last resort maildrop tries to open $HOME/.mailfilters/default.
223 For example, if the parameter to the -M option is
225 mailfilter-lists-maildrop, maildrop will try to open the following
226 files, in order:
227 Note that maildrop looks for -default files ONLY if -M is used.
229 -D uuu/ggg
231 This option is reserved for use by the version of maildrop that
232 comes integrated with the Courier mail server[1].
233 -V level
235 Initialize the VERBOSE variable to level. Because maildrop parses
236 the entire before running it, this option is used to produce
237 debugging output in the parsing phase. Otherwise, if filename has
238 syntax errors, then no debugging output is possible because the
239 VERBOSE variable is not yet set.
240 -V is ignored when maildrop runs in delivery mode.
243 -w N
245 The -w N option places a warning message into the maildir if the
246 maildir has a quota setting, and after the message was successfully
247 delivered the maildir was at least N percent full. The warning
248 message is copied verbatim from /etc/quotawarnmsg with the addition
249 of the "Date:" and "Message-Id:" headers. The warning is repeated
250 every 24 hours (at least), until the maildir drops below N percent
251 full.
252
254 If a filename is not specified on the command line, or if the -d option
255 is used, maildrop will run in delivery mode. In delivery mode, maildrop
256 changes to the home directory of the user specified by the -d option
257 (or the user who is running maildrop if the -d option was not given)
258 and reads $HOME/.mailfilter for filtering instructions.
259 $HOME/.mailfilter must be owned by the user, and have no group or
260 global permissions (maildrop terminates if it does).
261 If $HOME/.mailfilter does not exist, maildrop will simply deliver the
263 message to the user's mailbox.
264 If the file /etc/maildroprc exists, maildrop reads filtering
266 instructions from this file first, before reading $HOME/.mailfilter.
267 This allows the system administrator to provide global filtering
268 instructions for all users.
269 Note
271 /etc/maildroprc is read only in delivery mode.
272
274 The -d option can also specify a name of a virtual account or mailbox.
275 See the makeuserdb(1) manual page in the Courier Authentication
276 library's documentation for more information.
277
279 The embedded mode is used when maildrop's filtering abilities are
280 desired, but no actual mail delivery is needed. In embedded mode
281 maildrop is executed by another application, and is passed the -m or
282 the -M option.[5] maildrop reads the message, then runs the filtering
283 rules specified in filename.
284 filename may contain any filtering instructions EXCEPT the following:
286 ` ... `
288 Text strings delimited by back-tick characters (run shell command)
289 are not allowed.
290 cc[6]
292 The cc command is not allowed in embedded mode.
293 dotlock[7]
295 The dotlock command is not allowed in embedded mode.
296 flock[8]
298 The flock command is not allowed in embedded mode.
299 gdbmopen[9]
301 In embedded mode, GDBM databases may be opened only for reading.
302 log[10]
304 The log command is not allowed in embedded mode.
305 logfile[10]
307 The logfile command is not allowed in embedded mode.
308 to[11]
310 The to command is not allowed in embedded mode.
311 xfilter[12]
313 The xfilter command is not allowed in embedded mode.
314 Normally when the filename does not explicitly delivers a message,
316 maildrop will deliver the message to the user's default mailbox. This
317 is also disabled in embedded mode.
318 The filename may communicate with the parent application by using the
320 echo[13] statement and the EXITCODE environment variable.
321 /etc/maildroprcs
323 If maildrop encounters an include[14] statement where the filename
324 starts with /etc/maildroprcs/, the normal restrictions for the embedded
325 mode are suspended while executing the filter file in the
326 /etc/maildroprcs directory. The restrictions are also suspended for any
327 additional filter files that are included from /etc/maildroprcs. The
328 restrictions resume once maildrop finishes executing the file from
329 /etc/maildroprcs.
330 This allows the system administrator to have a controlled environment
332 for running external commands (via the backticks, or the xfilter[12]
333 command).
334 The name of the file may not contain any periods (so that a creative
336 individual can't write include
337 "/etc/maildroprcs/../../home/user/recipe").
338 Before executing the commands in the /etc/maildroprcs file, maildrop
340 automatically resets the following variables to their initial values:
341 DEFAULT, HOME, LOCKEXT, LOCKSLEEP, LOCKTIMEOUT, LOCKREFRESH, LOGNAME,
342 PATH, SENDMAIL, and SHELL. Please note that the previous values of
343 these variables (if they were changed) will NOT be restored once
344 maildrop finishes executing the commands from /etc/maildroprcs.
345
347 maildrop has a watchdog timer that attempts to abort runaway filtering.
348 If filtering is not complete within a predefined time interval (defined
349 by the system administrator, usually five minutes), maildrop
350 terminates.
351
353 /etc/passwd
354 Sets user's home directory, and related variables. If NIS/YP is
355 install, that will be used as well.
356 /etc/maildroprc
358 Global filtering instructions for delivery mode.
359 /var/mail
361 System mailbox (actual directory defined by the system
362 administrator).
363 /usr/lib/sendmail
365 Program to forward mail (exact program defined by the system
366 administrator).
367 $HOME/.mailfilter
369 Filtering instructions in delivery mode.
370 $HOME/.mailfilters
372 Directory containing files used in special embedded mode.
373
375 lockmail(1)[15], maildropfilter(7)[16], makedat(1)[17],
376 maildropgdbm(7)[9], maildropex(7)[18], reformail(1)[19],
377 makemime(1)[20], reformime(1)[21], egrep(1), grep(1), , courier(8)[22],
378 sendmail(8), http://www.qmail.org.
379
381 1. Courier
382 http://www.courier-mta.org
383 2. Qmail
385 http://www.qmail.org
386 3. "Environment"
388 maildropfilter.html#environment
389 4. "Variable substitution"
391 maildropfilter.html#varsubst
392 5. is passed the -m or the -M option.
394 #options
395 6. cc
397 maildropfilter.html#cc
398 7. dotlock
400 maildropfilter.html#dotlock
401 8. flock
403 maildropfilter.html#flock
404 9. gdbmopen
406 maildropgdbm.html
407 10. log
409 maildropfilter.html#log
410 11. to
412 maildropfilter.html#to
413 12. xfilter
415 maildropfilter.html#xfilter
416 13. echo
418 maildropfilter.html#echo
419 14. include
421 maildropfilter.html#include
422 15. lockmail(1)
424 lockmail.html
425 16. maildropfilter(7)
427 maildropfilter.html
428 17. makedat(1)
430 makedat.html
431 18. maildropex(7)
433 maildropex.html
434 19. reformail(1)
436 reformail.html
437 20. makemime(1)
439 makemime.html
440 21. reformime(1)
442 reformime.html
443 22. courier(8)
445 courier.html
446Double Precision, Inc. 04/22/2007 MAILDROP(1)