because i didn't find any solution to monitor zimbra with nagios i wrote a small script. It's interprets the output of "zmcontrol status" command. Because the zmcontrol can only be startet from the zimbra account you have to edit sudoers file like.
%nagios ALL=(zimbra) NOPASSWD:/opt/zimbra/bin/zmcontrol
small (german) article on my blogsite at: Schose’s Blog » Blog Archive » Zimbra Monitoring mit Nagios
Is it reliable enough to monitor this command? Do you have some other ideas to improve monitoring?? comments welcome!