Fetchmail for Debian, README file
$Id: README.Debian 228 2005-08-14 15:52:49Z nion $

Miscellaneous notes
-------------------

Fetchmail wants a MTA and will not use a MDA fallback by default anymore.
Please configure it correctly for your system.

Also, MTA return codes 552 and 553 always cause fetchmail to trash the message,
unless "keep" mode is being used. MTA return codes in the "antispam" option
list will also cause mail loss. However, this list is empty by default.


Build instructions
------------------

Make sure to run "debian/rules clean" BEFORE you try to build the package
(dpkg-buildpackage will do that for you). You have been warned.

You can tailor the capabilities of fetchmail (e.g. to add Kerberos IV support)
by defining DEB_FETCHMAIL_BUILD_OPTIONS before building the package. There is
no need to edit debian/rules anymore. Please read the comments in debian/rules
for more information.

Building KerberosV support using the Heimdal libs in Debian will only work in
the SSL version of fetchmail.


Fetchmail and losing mail
-------------------------

POP3 servers are known to delete stored mail for no good reason, no matter what
it is told to do. Badly-configured MTAs are known to send email to the trash or
bounce it with spam return codes -- including email sent to the postmaster. And
fetchmail is known to be blamed for both these things causing mail loss.

SEND EMAIL TO YOURSELF MANUALLY TROUGH WHICHEVER DELIVERY METHOD YOU WANT
FETCHMAIL TO SEND THROUGH, TO TEST IT BEFORE RUNNING FETCHMAIL.

CHECK YOUR MTA AND POP3 SERVER BY TELLING FETCHMAIL NOT TO DELETE MAIL FROM
YOUR SERVER ("keep" option) NOR DELETE SPAM ("antispam -1") NOR BOUNCE MAIL
("set no bouncemail") IF YOU VALUE YOUR EMAIL. YOU HAVE BEEN WARNED.

The above checks should be made every time you change something important in
either fetchmail's or the MTA/MDA configuration.

Now, let's go over it once again: Fetchmail can, and will delete your mail if
it thinks the MTA is telling it to do so. Option "keep" will avoid the
deletion of messages. If you forget to tell fetchmail to "keep" messages, and
the MTA refuses delivery (particularly with codes 552 (message too large) or 553
(invalid envelope sender), fetchmail will delete the message even when it
failed to deliver it. Setting "no bouncemail" and "antispam -1" makes such
deletion less likely.


Using the system-wide fetchmail
-------------------------------

The fetchmail package install a SysV init script in /etc/init.d/fetchmail.
This script will start a fetchmail daemon running as the user fetchmail, if
the configuration file /etc/fetchmailrc is present in the system. If the
configuration file is not present, nothing is started.

If the system-wide fetchmail refuses to start, you probably have syntax
errors in the /etc/fetchmailrc file. Try /etc/init.d/fetchmail debug-run
to find out why it is not starting. Do notice that debug-run is *not*
capable of detecting errors that happen only in daemon mode.

By default, the system-wide fetchmail daemon will poll every 5 minutes. To
change this, add a line like the following to your /etc/fetchmailrc file:

  set daemon 900     # poll every 15 minutes

Also, the system-wide fetchmail daemon will by default log all output to
syslog. To disable this (e.g. if you use the logfile option), add the
following to your /etc/fetchmailrc file:

  set no syslog      # disable logging to syslog


Fetchmail on a PPP link
-----------------------

By default, the system-wide fetchmail will start at boot, and will be
restarted when the PPP link is brought up. You, can however, configure
the system-wide fetchmail to *only* run when the PPP link is up (note
that this has no real advantage over running fetchmail all the time). To
do so, you must do four things:

  1. Turn of fetchmail at boot. Simply rename the S99fetchmail links in
     the /etc/rc?.d directories to K15fetchmail. For example:

    # cd /etc/rc2.d
    # mv S99fetchmail K15fetchmail

    Under Debian, it is advised to use generic commands:
    # invoke-rc.d fetchmail stop
    # update-rc.d fetchmail remove

  2. Edit the ip-up script as described in the comments.

  3. Edit the ip-down script as describe in the comments.

  4. Remove /etc/resolvconf/update-libc.d/fetchmail (or add an "exit 0"
     line at the beginning).

Note that both the init script and the fetchmail PPP scripts are conffiles,
so if you don't like the setup you just need to change them to your heart's
content. The changes will not be overwritten by a package upgrade without
your explicit consent.


Running the system-wide fetchmail as root
-----------------------------------------

The fetchmail package no longer supports running the system-wide fetchmail
as root. To switch to the new init script facility, just move your
/root/.fetchmailrc to /etc/fetchmailrc, read the "UIDL cache" section below,
and run:

  invoke-rc.d fetchmail restart


The UIDL cache
--------------

Fetchmail has an UIDL cache it may use to track message-seen state. The
init script and ip-up scripts want this cache to be in
/var/mail/.fetchmail-UIDL-cache. Note the paths leading up to the UIDL
cache file must be readable by the fetchmail user. This should not be a
problem on a default Debian install.


Errors with POP3 servers
------------------------

If you have difficulties with your POP3 server, and fetchmail -v shows that
fetchmail is trying to use AUTH instead of USER and PASS, you can use
"auth password" to force the use of USER and PASS. Also, fetchmailconf has
a blacklist of known-bad servers, try autodetecting the server with it.


Reporting problems
------------------

Use a Debian bug-reporting tool (e.g. reportbug from the reportbug package) to
report problems. Please include a fetchmail -v -v dump showing the problem to
aid debugging. /etc/init.d/fetchmail debug-run will do that for you if you are
using the system-wide fetchmail feature (Do remember that problems that only
happen in daemon mode are NOT triggered by debug-run).

Problems with signals (e.g. "why fetchmail aborts with SIGPIPE?") need the use
of strace for debugging. Just do:

  /etc/init.d/fetchmail debug-run strace -o /tmp/strace.out

and the init script will run fetchmail, and store the strace output in
/tmp/strace.out. See strace(1) for more details on strace.

WARNING: strace output may contain security-sensitive information, such as your
fetchmail passwords. You should clobber those with "*" or "X" before sending
the file to anyone, especially the Debian bug-tracking system.

 -- Nicolas Boulenguez <nicolas@debian.org>, Tue, 10 Apr 2018 15:26:22 +0200
