If Plugin “postfix_mailstats” exited with status 768 occured, delete the /var/lib/munin/plugin-state/munin-plugin-postfix_mailstats.state file.

http://munin.projects.linpro.no/
http://wiki.kartbuilding.net/index.php/Munin_Statistics
http://muninexchange.projects.linpro.no/
http://dlog.gal.dk/