1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
|
<!doctype HTML public "-//W3O//DTD W3 HTML 2.0//EN">
<HTML>
<HEAD>
<TITLE>The Fetchmail FAQ</TITLE>
<link rev=made href=mailto:esr@snark.thyrsus.com>
<meta name="description" content="Frequently asked questions about fetchmail.">
<meta name="keywords" content="fetchmail, POP, IMAP, remote mail">
</HEAD>
<BODY>
<H1>Frequently Asked Questions About Fetchmail</H1>
$Id: fetchmail-FAQ.html,v 1.5 1997/04/17 08:06:04 esr Exp $<p>
(Added <a href="http:#C6">C6</a> on working with qmail and
<a href="http:#C7">C7</a> on managing fetchmail in the presence of
multiple login sessions.)<p>
Before reporting any bug, please read <a href="#G3">G3</a> for advice
on how to include diagnostic information that will get your bug fixed
as quickly as possible. <p>
If you have a question or answer you think ought to be added to this FAQ list,
mail it to fetchmail's maintainer, Eric S. Raymond, at
<A HREF="mailto:esr@thyrsus.com">esr@snark.thyrsus.com</A>.<p>
There is a fetchmail-friends reflector for people who want to discuss fixes
and improvements in fetchmail. It's at
<a href="mail:fetchmail-friends@thyrsus.com">fetchmail-friends@thyrsus.com</a>
and is a SmartList reflector; sign up in the usual way. <p>
<h1>General questions:</h1>
<a href="#G1">G1. What is fetchmail and why should I bother?</a><br>
<a href="#G2">G2. Where do I find the latest FAQ and fetchmail sources?</a><br>
<a href="#G3">G3. I think I've found a bug. Will you fix it?</a><br>
<a href="#G4">G4. I have this idea for a neat feature. Will you add it?</a><br>
<h1>Build-time problems:</h1>
<a href="#B1">B1. My C compiler libraries don't seem to have atexit(3).</a><br>
<a href="#B2">B2. Building fetchmail fails with compiler errors in error.c.</a><br>
<h1>Fetchmail configuration file grammar questions:</h1>
<a href="#F1">F1. Why does my .fetchmailrc from 2.8 or earlier no longer work?</a><br>
<a href="#F2">F2. The .fetchmailrc parser won't accept my all-numeric user name.</a><br>
<a href="#F3">F3. What does "Warning: user entry with no `user' keyword" mean?</a><br>
<a href="#F4">F4. I'm migrating from popclient. How do I need to modify my .poprc?</a><br>
<h1>Configuration questions:</h1>
<a href="#C1">C1. Why do I need a .fetchmailrc when running as root on my own machine?</a><br>
<a href="#C2">C2. How can I arrange for a fetchmail daemon to get killed when I log out?</a><br>
<a href="#C3">C3. How do I know what interface and address to use with --interface?</a><br>
<a href="#C4">C4. How can I get fetchmail to work with ssh?</a><br>
<a href="#C5">C5. How can I set up support for sendmail's anti-spam 571 response?</a><br>
<a href="#C6">C6. How can I use fetchmail with qmail?</a><br>
<a href="#C7">C7. How can I do automatic startup/shutdown of fetchmail
when I may have multiple login sessions going?</a><br>
<h1>Runtime fatal errors:</h1>
<a href="#R1">R1. I think I've set up fetchmail correctly, but I'm not getting any mail.</a><br>
<a href="#R2">R2. Fetchmail isn't working, and -v shows `SMTP connect failed' messages.</a><br>
<a href="#R3">R3. When I try to configure an MDA, fetchmail doesn't work.</a><br>
<a href="#R4">R4. Fetchmail dumps core in -V mode, but operates normally otherwise.</a><br>
<a href="#R5">R5. Fetchmail dumps core when I use a .netrc file but works otherwise.</a><br>
<a href="#R6">R6. Mail that was being fetched when I interrupted my fetchmail seems to have been vanished.</a></br>
<h1>Multidrop-mode problems:</h1>
<a href="#M1">M1. I've declared local names, but all my multidrop mail is going to root anyway.</a><br>
<a href="#M2">M2. I can't seem to get fetchmail to route to a local domain properly.</a><br>
<a href="#M3">M3. I tried to run a mailing list using multidrop, and I have a mail loop!</a><br>
<a href="#M4">M4. My multidrop fetchmail seems to be having DNS problems.</a><br>
<a href="#M5">M5. I'm seeing long DNS delays before each message is processed.</a><br>
<h1>Mangled mail:</h1>
<a href="#X1">X1. Why is fetched mail being logged with my name, not the real From address?</a><br>
<a href="#X2">X2. Spurious blank lines are appearing in the headers of fetched mail.</a><br>
<a href="#X3">X3. My mail client can't see a Subject line.</a><br>
<a href="#X4">X4. Messages containing "From" at start of line are being split.</a><br>
<h1>Answers:</h1>
<hr>
<h2><a name="G1">G1. What is fetchmail and why should I bother?</a></h2>
Fetchmail is a one-stop solution to the remote mail retrieval problem
for Unix machines, quite useful to anyone with an intermittent PPP or
SLIP connection to a remote mailserver. It can collect mail using any
variant of POP or IMAP and forwards via port 25 to the local SMTP
listener, enabling all the normal forwarding/filtering/aliasing
mechanisms that would apply to local mail or mail arriving via a
full-time TCP/IP connection.<p>
Fetchmail is not a toy or a coder's learning exercise, but an
industrial-strength tool capable of transparently handling every
retrieval demand from those of a simple single-user ISP connection up
to mail retrieval and rerouting for an entire client domain.
Fetchmail is easy to configure, unobtrusive in operation, powerful,
feature-rich, and well documented. Extensive testing by a large,
multi-platform user community has shown that it is as near bulletproof
as the underlying protocols permit.<p>
If you found this FAQ in the distribution, see the README for fetchmail's
full feature list.<p>
<hr>
<h2><a name="G2">G2. Where do I find the latest FAQ and fetchmail
sources?</a></h2>
The latest HTML faq is available alongside the latest fetchmail
sources at Eric S. Raymond's free software page:
<a href="http://www.ccil.org/~esr/esr-freeware.html">
http://www.ccil.org/~esr/esr-freeware.html</a>. You can also find
both in the <a
href="http://sunsite.unc.edu/pub/Linux/system/mail/pop/!INDEX.html">POP
mail tools directory on Sunsite</a>.<p>
A text dump of this FAQ is included in the fetchmail
distribution. Because it freezes at distribution release time, it may
not be completely current.<p>
<hr>
<h2><a name="G3">G3. I think I've found a bug. Will you fix it?</a></h2>
Yes I will, provided you include enough diagnostic information for me
to go on. When reporting bugs, please include the following:
<ol>
<li>Your operating system and compiler version.
<li>The release and patch level of the fetchmail you are running. You can see
your patchlevel by typing `fetchmail -V'.
<li>The output of fetchmail -V (this will not reveal your password).
<li>Any command-line options you used.
</ol>
It is helpful if you include your .fetchmailrc, but not necessary
unless your symptom seems to involve an error in configuration parsing.<p>
A transcript of the failed session with -v on is almost always useful.
If the bug involves a core dump or hang, a gdb stack trace is good to have.
(Bear in mind that you can attach gdb to a running but hung process by
giving the process ID as a second argument.)<p>
Best of all is a mail file which, when fetched, will reproduce the
bug.<p>
Any bug I can reproduce will usually get fixed very quickly, often
within 48 hours. Bugs I can't reproduce are a crapshoot. If the
solution isn't obvious when I first look, it may evade me for a long
time (or to put it another way, fetchmail is well enough tested that the
easy bugs have long since been found). So if you want your bug fixed
rapidly, it is not just sufficient but nearly <em>necessary</em> that
you give me a way to reproduce it.<p>
<hr>
<h2><a name="G4">G4. I have this idea for a neat feature. Will you add it?</a></h2>
Probably not. Most of the feature suggestions I get are for ways to
set various kinds of administrative policy or add more spam filtering
(the most common one, which I used to get about four million times a week
and got <em>really</em> tired of, is for tin-like kill files).<p>
You can do spam filtering better with procmail or mailagent on the
server side and (if you're the server sysadmin) sendmail.cf domain
exclusions. You can do other policy things better with the
<tt>mda</tt> option and script wrappers around fetchmail. If
it's a prime-time-vs.-non-prime-time issue, ask yourself whether a
wrapper script called from crontab would do the job.<p>
I'm not going to do these; fetchmail's job is transport, not policy, and I
refuse to change it from doing one thing well to attempting many things badly.
One of my objectives is to keep fetchmail simple so it stays reliable.<p>
All that said, if you have a feature idea that really is about a transport
problem that can't be handled anywhere but fetchmail, lay it on me. I'm
very accommodating about good ideas.<p>
<hr>
<h2><a name="B1">B1. My C compiler libraries don't seem to have atexit(3).</a></h2>
Your compiler libraries are deficient (this has been reported from a
bunch of older Solaris and SCO boxes). The <em>atexit(3)</em>
function is part of the ANSI C standard and should be there.<p>
You may be able to find a linkable object for <em>atexit(3)</em> in your C++
library. If not, I recommend installing the GNU C library and/or GCC
itself. You can find a copy of the GNU C library (which is fully
ANSI-compliant and supplies ANSI-compliant headers as well) at <a
href="ftp://prep.ai.mit.edu/pub/gnu/glibc-1.09.1.tar.gz">ftp://prep.ai.mit.edu/pub/gnu/glibc-1.09.1.tar.gz</a><p>
If you are a SunOS user and cannot install glibc, Chris Cheyney <<A
HREF="mailto:cheyney@netcom.com">cheyney@netcom.com</A>> has
developed a <A
HREF="http://www.cjnetworks.com/~cheyney/me/atexit.html"> patch</A>
that adds <em>atexit</em> to the fetchmail code itself. <p>
<hr>
<h2><a name="B2">B2. Building fetchmail fails with compiler errors in error.c</a></h2>
We've had reports of this from under SunOS, Solaris 2.5, HP-UX and
NEXTSTEP 3.3. All but the HP-UX problem seems to have abated after
3.8. You may have to turn off HAVE_VSYSLOG manually.<p>
<hr>
<h2><a name="F1">F1. Why does my .fetchmailrc from 2.8 or earlier no longer work?</a></h2>
The `<tt>interface</tt>', `<tt>monitor</tt>' and
`<tt>batchlimit</tt>' options have changed.<p>
They used to be global options with `set' syntax like the batchlimit
and logfile options. Now they're per-server options, like `protocol'.<p>
If you had something like<p>
<pre>
set interface = "sl0/10.0.2.15"
</pre>
in your .fetchmailrc file, simply delete that line and insert
`interface sl0/10.0.2.15' in the server options part of your `defaults'
declaration.<p>
Do similarly for any `<tt>monitor</tt>' or `<tt>batchlimit</tt>' options.<p>
<hr>
<h2><a name="F2">F2. The .fetchmailrc parser won't accept my all-numeric user name.</a></h2>
So put string quotes around it. :-)<p>
The configuration file parser treats any all-numeric token as a
number, which will confuse it when it's expecting a name. String
quoting forces the token's class.<p>
<hr>
<h2><a name="F3">F3. What does "Warning: user entry with no `user' keyword" mean?</a></h2>
This warning means that you're using a .fetchmailrc that's
written in the old popclient syntax without an explicit `username'
keyword leading the first user entry attached to a server entry.<p>
This can be triggered by having a user option such as `<tt>keep</tt>'
or `<tt>fetchall</tt>' before the first explicit username. For
example, if you write<p>
<pre>
poll openmail protocol pop3
keep user "Hal DeVore" there is hdevore here
</pre>
the `<tt>keep</tt>' option will generate an entire user entry with the default
username (the name of fetchmail's invoking user).<p>
The popclient compatibility syntax is deprecated and may be removed in
a future version. (It complicates the configuration file grammar and
confuses users.)<p>
<hr>
<h2><a name="F4">F4. I'm migrating from popclient. How do I need to modify my .poprc?</a></h2>
If you have been using popclient (the ancestor of this program)
at version 3.0b6 or later, start with this<p>
<pre>
(cd ~; mv ~/.poprc ~/.fetchmailrc)
</pre>
in order to migrate. Be aware that some of popclient's unnecessary
options have been removed (see the NOTES file in the distribution for
explanation). You can't deliver to a local mail file anymore or to
standard output any more, and using an MDA for delivery is
discouraged. If you throw those options away, fetchmail will now
forward your mail into your system's normal Internet-mail delivery
path.<p>
Actually, using an MDA is now almost always the wrong thing; the MDA
facility has been retained only for people who can't or won't run a
sendmail-like SMTP listener on port 25. The default, SMTP forwarding
to port 25, is better for at least two major reasons. One: it feeds
retrieved POP and IMAP mail into your system's normal delivery path
along with local mail and normal Internet mail, so all your normal
filtering/aliasing/forwarding setup for local mail works. Two:
because the port 25 listener returns a positive acknowledge, fetchmail
can be sure you're not going to lose mail to a disk-full or some other
resource-exhaustion problem.<p>
If you used to use <tt>-mda "procmail -d</tt>
<em><you></em><tt>"</tt> or something similar, forward to port
25 and do "<tt>| procmail -d</tt> <em><you></em><tt>"</tt> in
your ~/.forward file.<p>
As long as your new .fetchmailrc file does not use the removed
`localfolder' option or `<tt>limit</tt>' (which now takes a maximum byte size
rather than a line count), a straight move or copy of your .poprc will
often work. (The new run control file syntax also has to be a little
stricter about the order of options than the old, in order to support
multiple user descriptions per server; thus you may have to rearrange
things a bit.)<p>
Run control files in the minimal .poprc format (without the `username'
token) will trigger a warning. To eliminate this warning, add the
`<tt>username</tt>' keyword before your first user entry per server (it is
already required before second and subsequent user entries per server.<p>
In some future version the `<tt>username</tt>' keyword will be required.<p>
<hr>
<h2><a name="C1">C1. Why do I need a .fetchmailrc when running as root on my own machine?</a></h2>
Ian T. Zimmerman <itz@rahul.net> asked:<p>
On the machine where I'm the only real user, I run fetchmail as root
from a cron job, like this:<p>
<pre>
fetchmail -u "itz" -p POP3 -s bolero.rahul.net
</pre>
This used to work as is (with no .fetchmailrc file in root's home
directory) with the last version I had (1.7 or 1.8, I don't
remember). But with 2.0, it RECPs all mail to the local root user,
unless I create a .fetchmailrc in root's home directory containing:<p>
<pre>
skip bolero.rahul.net proto POP3
user itz is itz
</pre>
It won't work if the second line is just "<tt>user itz</tt>". This is silly.<p>
It seems fetchmail decides to RECP the `default local user' (ie. the
uid running fetchmail) unless there are local aliases, and the
`default' aliases (itz->itz) don't count. They should.<p>
Answer:<p>
No they shouldn't. I thought about this for a while, and I don't much
like the conclusion I reached, but it's unavoidable. The problem is
that fetchmail has no way to know, in general, that a local user `itz'
actually exists.<p>
"Ah!" you say, "Why doesn't it check the password file to see if the remote
name matches a local one?" Well, there are two reasons.<p>
One: it's not always possible. Suppose you have an SMTP host declared
that's not the machine fetchmail is running on? You lose.<p>
Two: How do you know server itz and SMTP-host itz are the same person?
They might not be, and fetchmail shouldn't assume they are unless
local-itz can explicitly produce credentials to prove it (that is, the
server-itz password in local-itz's .fetchmailrc file.).<p>
Once you start running down possible failure modes and thinking about
ways to tinker with the mapping rules, you'll quickly find that all the
alternatives to the present default are worse or unacceptably
more complicated or both.<p>
<hr>
<h2><a name="C2">C2. How can I arrange for a fetchmail daemon to get killed when I log out?</a></h2>
Fetchmail versions before 2.3 actually used SIGHUP as a wakeup signal.
Newer versions use SIGUSR1 for wakeup (and SIGHUP only in
background-daemon mode) in order to avoid any potential confusion
about logout-time behavior. The right way to dispatch fetchmail on
logout is to arrange for the command `fetchmail -q' to be called on
logout.<p>
Under bash, you can arrange this by putting `fetchmail -q' in the file
`~/.bash_logout'. Most csh variants execute `~/.logout' on logout.
For other shells, consult your shell manual page.<p>
<hr>
<h2><a name="C3">C3. How do I know what interface and address to use with --interface?</a></h2>
This depends a lot on your local networking configuration (and right
now you can't use it at all except under Linux). However, here are
some important rules of thumb that can help. If they don't work, ask
your local sysop or your Internet provider.<p>
First, you may not need to use --interface at all. If your machine
only ever does SLIP or PPP to one provider, it's almost certainly by a
point to point modem connection to your provider's local subnet that's
pretty secure against snooping (unless someone can tap your phone or
the provider's local subnet!). Under these circumstances, specifying
an interface address is fairly pointless.<p>
What the option is really for is sites that use more than one
provider. Under these circumstances, typically one of your provider
IP addresses is your mailserver (reachable fairly securely via the
modem and provider's subnet) but the others might ship your packets
(including your password) over unknown portions of the general
Internet that could be vulnerable to snooping. What you'll use
--interface for is to make sure your password only goes over the
one secure link.<p>
To determine the device:<p>
<ol>
<li> If you're using a SLIP link, the correct device is probably sl0.
<li> If you're using a PPP link, the correct device is probably ppp0.
<li> If you're using a direct connection over a local network such as
an ethernet, use the command `netstat -r' to look at your routing table.
Try to match your mailserver name to a destination entry; if you don't
see it in the first column, use the `default' entry. The device name
will be in the rightmost column.
</ol>
To determine the address and netmask:<p>
<ol>
<li> If you're talking to slirp, the correct address is probably 10.0.2.15,
with no netmask specified. (It's possible to configure slirp to present
other addresses, but that's the default.)
<li> If you have a static IP address, run `ifconfig <device>', where <device>
is whichever one you've determined. Use the IP address given after
"inet addr:". That is the IP address for your end of the link, and is
what you need. You won't need to specify a netmask.
<li> If you have a dynamic IP address, your connection IP will vary randomly
over some given range (that is, some number of the least significant bits
change from connection to connection). You need to declare an address
with the variable bits zero and a complementary netmask that sets
the range.
</ol>
To illustrate the rule for dynamic IP addresses, let's suppose you're
hooked up via SLIP and your IP provider tells you that the dynamic
address pool is 255 addresses ranging from 205.164.136.1 to
205.164.136.255. Then<p>
<pre>
interface "sl0/205.164.136.0/255.255.255.0"
</pre>
would work. To range over any value of the last two octets
(65536 addresses) you would use<p>
<pre>
interface "sl0/205.164.0.0/255.255.0.0"
</pre>
<hr>
<h2><a name="C4">C4. How can I get fetchmail to work with ssh?</a></h2>
This is a lightly edited version of a recipe from Masafumi NAKANE.<p>
1. You must have ssh (the ssh client) on the local host and sshd (ssh
server) on the remote mail server. And, you have to configure ssh so
you can login to the sshd server host without a password. (Refer to ssh
man page for several authentication methods.)<p>
2. Add something like following to your .fetchmailrc file: <p>
<pre>
poll localhost port 1234 with pop3:
preconnect "ssh -f -L 1234:mailhost:110 mailhost sleep 20 </dev/null >/dev/null";
</pre>
(Note that 1234 can be an arbitrary port number. Privileged ports can
be specified only by root.) The effect of this ssh command is to
forward connections made to localhost port 1234 (in above example) to
mailhost's 110.<p>
This configuration will enable secure mail transfer. All the
conversation between fetchmail and remote pop server will be
encrypted.<p>
If sshd is not running on the remote mail server, you can specify
intermediate host running it. If you do this, however, communication
between the machine running sshd and the POP server will not be encrypted.
And the preconnect line would be like this:<p>
<pre>
preconnect "ssh -f -L 1234:mailhost:110 sshdhost sleep 20 </dev/null >/dev/null"
</pre>
You can work this trick with IMAP too, but the port number 110 in the
above would need to become 143.<p>
<hr>
<h2><a name="C5">C5. How can I set up support for sendmail's anti-spam 571 response?</a></h2>
Rachel Polanskis <r.polanskis@nepean.uws.edu.au> writes:<p>
Basically you need to use the "check_*" rules in sendmail.
These are rules introduced since version 8.8.2<p>
The idea is to generate a list of domains and addresses that are placed into
a file - I call mine "sendmail.rej" and you place just one domain
or email address on each line. During the SMTP transaction, this file
is checked and if there is a match, the message is refused, with
a suitable "Service not available" message sent back to the sender.<p>
With the feature enabled in fetchmail, the mail is simply deleted,
with no further processing.<p>
The only drawback when blocking spam with fetchmail is that you
do not get the satisfaction of sending an error back to the sender.<p>
To actually use the check_mail rules in sendmail 8.8.2 or better,
you need to know how to generate a sendmail.cf file from the m4
config files distributed with sendmail.<p>
The actual rules can be found at the following URLS:<p>
<a href="http://www.informatik.uni-kiel.de/%7Eca/email/check.html">
http://www.informatik.uni-kiel.de/%7Eca/email/check.html</a><p>
This one is by Claus Aßman, who has documented more of sendmail then
I can digest!
The actual setup I used though was by David Begley, who has put together
a WWW page describing how to quickly implement these rules yourself.<p>
<a href="http://www.nepean.uws.edu.au/users/david/pe/blockmail.html">
http://www.nepean.uws.edu.au/users/david/pe/blockmail.html</a><p>
David's pages could be moving shortly. I will post an update if it happens.<p>
Remember, when copying these rulesets off the web, that there are tabs
embedded in them, that may not be preserved. You <em>must</em> reintroduce
these tabs into the rules to make them work properly. <p>
Once you have your ruleset in place, and have generated a nice sendmail.cf
file, and the list of blocked sites, try telneting to your
SMTP port to test it, and send a message with a blocked address in it.<p>
You should see a message similar to:<p>
<pre>
"571 unsolicited email is refused"
</pre>
Next, if you have access to a host that you can send mail from, that
is <em>not</em> your mail host, add that host to your spamlist and
restart sendmail.<p>
Send a message to your mailing address from that host and then pop off
the message with fetchmail, using the -v argument. You can monitor
the SMTP transaction, and when the FROM address is parsed, if sendmail
sees that it is an address in spamlist, fetchmail will flush and
delete it.<p>
Under no circumstances put your <strong>mailhost</strong> or <strong>any host
you accept mail from</strong> using fetchmail into your reject file. You
<strong>will</strong> lose mail if you do this!!!<p>
The check_ rules work, and they work well. Coupled with fetchmail's
ability to respond to the appropriate error messages, you can be assured
of never seeing a spam from any address you put in the reject list.<p>
The only thing that is missing, as mentioned previously, is the ability
to allow sendmail to process the message further and generate an error
message to the sender. <p>
<hr>
<h2><a name="C6">C6. How can I use fetchmail with qmail?</a></h2>
Turn on the <tt>forcecr</tt> option; qmail's listener mode doesn't like
header or message lines terminated with bare linefeeds.<p>
(This information is thanks to Robert de Bath
<robert@mayday.cix.co.uk>.)<p>
If a mailhost is using the qmail package (see <a
href="http://pobox.com/~djb/qmail.html">http://pobox.com/~djb/qmail.html</a>)
then, providing the local hosts are also using qmail, it is possible
to setup one fetchmail link to be reliably collect the mail for an
entire domain.<p>
One of the basic features of qmail is the `Delivered-To:' message
header. Whenever qmail deliver a message to a local mailbox it puts
the username and hostname of the envelope recipient on this line. The
major reason for this is to prevent mail loops. <p>
To set up qmail to batch mail for a disconnected site the isp-mailhost
will have normally put that site in its `virtualhosts' control file so
it will add a prefix to all mail addresses for this site. This results
in mail sent to 'username@userhost.userdom.dom.com' having a
'Delivered-To:' line of the form:<p>
<listing>
Delivered-To: mbox-userstr-username@userhost.userdom.dom.com
</listing>
A single host maildrop will be slightly simpler:
<listing>
Delivered-To: mbox-userstr-username@userhost.dom.com
</listing>
The ISP can make the 'mbox-userstr-' prefix anything they choose
but a string matching the user host name is likely.<p>
To use this line you must:<p>
<ol>
<li>Ensure the option `envelope Delivered-To:' is in the fetchmail
config file.
<li>Ensure you have a localdomains containing 'userdom.dom.com' or
`userhost.dom.com' respectively.
</ol>
So far this reliably delivers messages to the correct machine of the
local network, to deliver to the correct user the 'mbox-userstr-'
prefix must be stripped off of the user name. This can be done by
setting up an alias within the qmail MTA on each local machine.
Simply create a dot-qmail file called '.qmail-mbox-userstr-default'
in the alias directory (normally /var/qmail/alias) with the contents:<p>
<listing>
| ../bin/qmail-inject -a -f"$SENDER" "${LOCAL#mbox-userstr-}@$HOST}"
</listing>
Note this <em>does</em> require a modern /bin/sh.<p>
<hr>
<h2><a name="R1">R1. I think I've set up fetchmail correctly, but I'm not getting any mail.</a></h2>
Maybe you have a .forward or alias set up that you've forgotten about. You
should probably remove it.<p>
Or maybe you're trying to run fetchmail in multidrop mode as root
without a .fetchmailrc file. This doesn't do what you think it
should; see question <a href="#C1">C1</a>.<p>
Or you may not be connecting to the SMTP listener. Run fetchmail -v
and see the next question.<p>
<hr>
<h2><a name="C7">C7. How can I do automatic startup/shutdown of fetchmail
when I may have multiple login sessions going?</h2>
In the contrib subdirectory of the fetchmail distribution there is
some shell code you can add yo your .bash_login and .bash_logout
profiles that will accomplish this. Thank James Laferriere
<babydr@nwrain.net> for it.<p>
<hr>
<h2>R2. Fetchmail isn't working, and -v shows `SMTP connect failed' messages.</a></h2>
Fetchmail is working, but your SMTP port 25 listener is down or inaccessible.
The first thing to check is if you can telnet to port 25 and get a greeting
line from the listener. If the listener is down, bring it back up.<p>
If the listener seems to be up when you test with telnet, it could
have had a momentary problem due to resource exhaustion (process table
full or some other problem that stopped the listener process from
forking). If your SMTP host is not `localhost' or something else in
/etc/hosts, the glitch could also have been caused by transient
nameserver failure, or the SMTP host's actually being down.<p>
If the listener tests up, you can usually ignore the glitch (except as
a symptom of other problems) because a future fetchmail run will get
the mail through. If this is a recurring or constant failure mode,
OTOH, you may have more serious problems in your network layer which I
can't diagnose in this FAQ.<p>
One way to work around chronic SMTP connect problems is to use --mda.
But this only attacks the symptom. You should really try to figure
out what's going on underneath before it bites you some other way. <p>
We have one report from a Linux user of 2.1 who solved his SMTP
connection problem by removing the reference to -lresolv from his link
line and relinking. Apparently in some recent Linux distributions the
libc bind library version works better.<p>
As of 2.2, the configure script has been hacked so the bind library is
linked only if it is actually needed. So under Linux it won't be, and
this particular cause should go away.<p>
<hr>
<h2><a name="R3">R3. When I try to configure an MDA, fetchmail doesn't work.</a></h2>
(I hear this one from people who have run into the blank-line problem in <a href="#X2">X2</a>.)<p>
Try sending yourself test mail and retrieving it using the
command-line options `<tt>-k -m cat</tt>'. This will dump exactly what
fetchmail retrieves to standard output. <p>
If the dump doesn't match what shows up in your mailbox when you
configure an MDA, your MDA is mangling the message. If it doesn't
match what you sent, then fetchmail or something on the server is
broken.<p>
<hr>
<h2><a name="R4">R4. Fetchmail dumps core in -V mode, but operates normally otherwise.</a></h2>
We've had this reported to us under Linux using libc-5.4.17 and gcc-2.7.2.
It does not occur with libc-5.3.12 or earlier versions.<p>
Workaround: link with GNU malloc rather than the stock C library malloc.<p>
We're told there is some problem with the malloc() code in that
version which makes it fragile in the presence of multiple free()
calls on the same pointer (the malloc arena gets corrupted).
Unfortunately it appears from doing gdb traces that whatever free()
calls producing the problem are being made by the C library itself, not the
fetchmail code (they're all from within fclose, and not an fclose called
by fetchmail, either).<p>
<hr>
<h2><a name="R5">R5. Fetchmail dumps core when I use a .netrc file but works otherwise.</a></h2>
We have a report that under Solaris 2.5, if fetchmail is compiled with -O2
or -O3, it segfaults on startup when reading a .netrc.<p>
You can work around this by dropping back to -O.<p>
There may be an actual bug here that the optimizer exposes; the stack
trace says the segfault is in free() and has all the earmarks of a heap-
corruption screw. But the symptom doesn't reproduce under Linux with the
same .fetchmailrc and .netrc.<p>
<hr>
<h2><a name="R6">R6. Mail that was being fetched when I interrupted my fetchmail seems to have been vanished.</a></h2>
Fetchmail only sends a delete mail request to the server when either
(a) it gets a positive delivery acknowledgement from the SMTP
listener, or (b) it gets an error 571 (the spam-filter error) from the
listener. No interrupt can cause it to lose mail.<p>
However, POP3 has a design problem in that its servers mark a message
`seen' as soon as the fetch command to get it is sent down. If for
some reason the message isn't actually delivered (you take a line hit
during the download, or your port 25 listener can't find enough free
disk space, or you interrupt the delivery in mid-message) that `seen'
message can lurk invisibly in your server mailbox forever.<p>
Workaround: add the `<tt>fetchall</tt>' keyword to your POP3 fetch options.<p>
Solution: switch to an IMAP server.<p>
<hr>
<h2><a name="M1">M1. I've declared local names, but all my multidrop
mail is going to root anyway.</a></h2>
Somehow your fetchmail is never matching the hostname part of
recipient names to the name of the mailserver machine. This probably
means it is unable to recognize hostname parts as being DNS names of
the mailserver, and may indicate some kind of DNS configuration
problem either on the server or your client machine. <p>
The easiest workaround is to write enough aka declarations to cover
all of your mailserver's aliases, then say `no dns'. This will take
DNS out of the picture (though it means mail may be uncollected if
it's sent to an alias of the server that you don't have listed). <p>
<hr>
<h2><a name="M2">M2. I can't seem to get fetchmail to route to a local domain properly.</a></h2>
A lot of people want to use fetchmail as a poor man's internetwork
mail gateway, picking up mail accumulated for a whole domain in a single
server mailbox and then routing based on what's in the To/Cc/Bcc lines.<p>
This is one of the things multidrop mode is for (though you
<em>are</em> going to get hurt by some mailing list software; see the
caveats under THE USE AND ABUSE OF MULTIDROP MAILBOXES on the man
page). If you want to try it, the way to do it is with the
`<tt>localdomains</tt>' option.<p>
In general, if you use localdomains you need to make sure of two other
things: <p>
<strong>1. You've actually set up your .fetchmailrc entry to invoke multidrop mode.</strong><p>
Many people set a `<tt>localdomains</tt>' list and then forget that fetchmail
wants to see more than one name (or the wildcard `*') in a `<tt>here</tt>' list
before it will do multidrop routing.<p>
<strong>2. You may have to set `no envelope'.</strong><p>
Normally, multidrop mode tries to deduce an envelope address from a message
before parsing the To/Cc/Bcc lines (this enables it to avoid losing to mailing
list software that doesn't put a recipient addess in the To lines).<p>
Some ways of accumulating a whole domain's messages in a single server
mailbox mean it all ends up with a single envelope address that is
useless for rerouting purposes. You may have to set `<tt>no
envelope</tt>' to prevent fetchmail from being bamboozled by this.<p>
<hr>
<h2><a name="M3">M3. I tried to run a mailing list using multidrop, and I have a mail loop!</a></h2>
This isn't fetchmail's fault. Check your mailing list. If the list
expansion includes yourself or anybody else at your mailserver (that is, not on
the client side) you've created a mail loop. Just chop the host part off any
local addresses in the list.<p>
If you use sendmail, you can check the list expansion with
<tt>sendmail -bv</tt>.<p>
<hr>
<h2><a name="M4">M4. My multidrop fetchmail seems to be having DNS problems.</a></h2>
We have one report from a Linux user (not the same one as in <a
href="#R2">R2</a>!) who solved this problem by removing the reference
to -lresolv from his link line and relinking. Apparently in some
recent Linux distributions the libc bind library version works
better.<p>
As of 2.2, the configure script has been hacked so the bind library is linked
only if it is actually needed. So under Linux it won't be, and this problem
should go away.<p>
<hr>
<h2><a name="M5">M5. I'm seeing long DNS delays before each message is processed.</a></h2>
Use the `<tt>aka</tt>' option to pre-declare as many of your
mailserver's DNS names as you can. When an address's host part
matches an aka name, no DNS lookup needs to be done to check it.<p>
If you're sure you've pre-declared all of your mailserver's DNS dames,
you can use the `<tt>no dns</tt>' option to prevent other hostname
parts from being looked up at all.<p>
Sometimes delays are unavoidable. Some SMTP listeners try to call DNS
on the From-address hostname as a way of checking that the address is valid.<p>
<hr>
<h2><a name="X1">X1. Why is fetched mail being logged with my name, not the real From address?</a></h2>
Because logging is done based on the address indicated by the sending
SMTP's MAIL FROM, and some listeners are picky about that address.<p>
Some SMTP listeners get upset if you try to hand them a MAIL FROM
address naming a different host than the originating site for your
connection. This is a feature, not a bug -- it's supposed to help
prevent people from forging mail with a bogus origin site. (RFC 1123
says you shouldn't do this exclusion...)<p>
Since the originating site of a fetchmail delivery connection is
localhost, this effectively means these picky listeners will barf on
any MAIL FROM address fetchmail hands them with an @ in it!<p>
In versions up to 1.9.9 this led to pesky errors at some sites.
Because of this, I hacked 2.0 to just use the calling user ID
as the MAIL FROM address.<p>
Versions 2.1 and up try the header From address first and fall back to
the calling-user ID. So if your SMTP listener isn't picky, the log
will look right.<p>
<hr>
<h2><a name="X2">X2. Spurious blank lines are appearing in the headers of fetched mail.</a></h2>
What's probably happening is that the POP/IMAP daemon on your
mailserver is inserting a non-RFC822 header (like X-POP3-Rcpt:) and
something in your delivery path (most likely an old version of the
<em>deliver</em> program, which sendmail often calls to do local delivery) is
failing to recognize it as a header.<p>
This is not fetchmail's problem. The first thing to try is installing
a current version of <em>deliver</em>. If this doesn't work, try to
figure out which other program in your mail path is inserting the
blank line and replace that. If you can't do either of these things,
pick a different MDA (such as procmail) and declare it with the
`<tt>mda</tt>' option.<p>
<hr>
<h2><a name="X3">X3. My mail client can't see a Subject line.</a></h2>
First, see <a href="#X2">X2</a>. This is quite probably the same
problem (X-POP3-Rcpt header or something similar being inserted by
the server and choked on by an old version of <em>deliver</em>).<p>
The O'Reilly sendmail book does warn that IDA sendmail doesn't process
X- headers correctly. If this is your problem, all I can suggest is
replacing IDA sendmail, because it's broken and not RFC822 conformant.<p>
<hr>
<h2>X4. Messages containing "From" at start of line are being split.</a></h2>
If you know the messages aren't split in your server mailbox, then this
is a problem with your POP/IMAP server, your client-side SMTP listener or
your local delivery agent. Fetchmail cannot split messages.<p>
Some POP daemons ignore Content-Length headers and split messages on
From lines. We have one report that the 2.1 version of the BSD popper
program (as distributed on Solaris 2.5 and elsewhere) is broken this way.<p>
You can test this. Declare an mda of `cat' and send yourself one
piece of mail containing "From" at start of a line. If you see a
split message, your POP/IMAP server is at fault. Upgrade to a more
recent version.<p>
Sendmail and other SMTP listeners don't split RFC822 messages either.
What's probably happening is either sendmail's local delivery agent or
your mail reader are not quite RFC822-conformant and are breaking
messages on what it thinks are Unix-style From headers. You can
figure out which by looking at your client-side mailbox with vi or
more. If the message is already split in your mailbox, your local
delivery agent is the problem. If it's not, your mailreader is the
problem.<p>
If you can't replace the offending program, take a look at your
sendmail.cf file. There will likely be a line something like<p>
<pre>
Mlocal, P=/usr/bin/procmail, F=lsDFMShP, S=10, R=20/40, A=procmail -Y -d $u
</pre>
describing your local delivery agent. Try inserting the `E' option in the
flags part (the F= string). This will make sendmail turn each dangerous
start-of-line From into a >From, preventing programs further downstream
from acting up.<p>
<HR>
<ADDRESS>Eric S. Raymond <A HREF="mailto:esr@thyrsus.com"><esr@snark.thyrsus.com></A></ADDRESS>
</BODY>
</HTML>
|
