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Revision 14 as of 2008-07-07 04:28:16


MemberManual / Email / EximFilter

This page explains how to use Exim's built-in per-user filtering system to sort your mail into different folders or deliver it elsewhere.


We use Exim as our mail daemon. It has a built-in filtering system that allows people to write a ".forward file" to give it custom instructions. Normally this is stored at ~/.forward, but at HCoop we store it at ~/.public/.forward to make it easier to keep the rest of your home directory private. So when we say ".forward" on the rest of this page, we mean ~/.public/.forward.

When email is delivered, the delivery process will run as the USER.daemon user, where USER is your HCoop username.

Delivering all mail to a different address

If you want email sent to your HCoop email address to be forwarded elsewhere, you can do that as follows.

Putting mail into separate folders

If you want to do anything more complicated than this, the exim project website has some good examples http://www.exim.org/exim-html-3.30/doc/html/filter_29.html. We also have an example .forward file in the following section.


Please note, an exim filter file, as opposed to a standard UNIX .forward file, must start with a line consisting exactly of the string "# Exim filter". This line is not an ordinary comment and any change will cause Exim to attempt to treat it as a list of forward addresses instead of a filter file.

Also, you should create and subscribe to any folders mentioned in these filters from within your IMAP client before installing these scripts.


It is possible to set up custom filters to do fancy things based on the X-Spam-Level: header. Here is NathanKennedy's ~/.public/.forward file. He finds that the default setting of 5.0 is too wimpy, and lets too much spam into his inbox. Virtually no ham that he gets scores less than 3.0, whereas a lot of spam scores less than 5.0, so he'd rather have anything over 3.0 go to his Junk folder. At the same time, he doesn't want to waste time, cycles, disk space or bandwidth with spam over 9.0. Most of his spam does score 9.0, and this goes straight to /dev/null (immediately disposed of) with this filter.

Finally, he has all HCoop list email go into a special HCoop folder.

Without further ado:

# Exim filter
logfile $home/.logs/mail/spamlog
if $header_subject contains "[HCoop"
    save $home/Maildir/.HCoop/
    "${if def:h_X-Spam-Level {def}{undef}}" is "def"
    if $h_X-Spam-Level: begins "\*\*\*\*\*\*\*\*\*"
    then save "/dev/null" 660
      if $h_X-Spam-Level: begins "\*\*\*"
      then save $home/Maildir/.Junk/
    "${if def:h_X-Spam-Flag {def}{undef}}" is "def"
    save $home/Maildir/.Junk/


# Exim filter
# Lists
if $h_to: contains "lists.hcoop.net"
        then save $home/Maildir/.Causes.Hcoop/
elif $h_to: contains "groups.barackobama.com"
        then save $home/Maildir/.Causes.Obama/
elif $h_X-Generated-By: CONTAINS "Launchpad"
        then save $home/Maildir/.Causes.Floss/
# Junk
elif $h_X-Spam-Level: begins "\*\*\*\*\*\*\*\*\*"
        then save "/dev/null" 660
elif $h_X-Spam-Level: begins "\*\*\*\*"
        then save $home/Maildir/.Junk.Spam/
elif $h_X-Spam-Status: contains "BAYES_99"
        then save $home/Maildir/.Junk.Bayes_99/

Filtering out bogus bounce messages

AdamChlipala found a trick a while back that allows you to filter out bogus bounce messages. https://lists.hcoop.net/pipermail/hcoop-discuss/2007-January/000745.html