The original postfix_mailqueue plugin delivered with munin does very well in many aspects. But it has a design related problem: to measure the number of mails per queue (active, incomming, deferred, ...) it counts the entries in the corresponding spool directories every 5 minutes (when munin core asks). If a mail only stays a short time in a queue (especially active and incomming queues) it won't get recognized by postfix_mailqueue.
Since on my low volume mailserver I'm interested in the total number of sent/ recieved messages in the last 5 minutes (for the deferred and hold queues the original method is good enough since a mail there probably stays longer than 5 minutes) I changed the behavior and meaning of the "active" and "incomming" graphs to "outgoing" (to the network) and "incomming" (from the network). To determine the number of mails for these graphs the recent (5 minutes, hardcoded) syslog entries are grep'ed for signaling sequences indicating some kind of action of postfix.
Clone this repository or download the postfix_mailqueue file and create a symlinkas root in /etc/munin/plugins by using e.g.:
cd /etc/munin/plugins; ln -s /your/path/to/postfix_mailqueue postfix_mailqueue
(In case you already used the original plugin you should remove the old symlink. Then wait about 10 minutes before add the new symlink described above.)
Next make sure that munin is allowed or at least allows this script to read your mail.log. How to do this depends on your system.
On Debian 6 mail.log is owned by root:adm and readable by nobody but them.
The recommended way here is to advice munin to run postfix_mailqueue with group
adm (and user postfix, by default) by modifying /etc/munin/plugin-conf.d/munin-node
where you should change/add a line to the [postfix_mailqueue] section:
group adm
If you use LMTP (e.g. with dovecot) and want to count delivery via LMTP as 'incoming' mail add another line with:
env.incoming_regex postfix/lmtp\\[.*status=sent
If your mail.log is not located at /var/log/mail.log (the default) you should add another line with your custom path:
env.maillog /var/log/mail.log
Don't forget to restart your munin-node deamon.
This little bash function returns the entries of a file (created in format of syslog default template; especially timestamp) of the last 5 minutes.