Zimbra is a messaging platform I started using recently. I have gathered some notes for what I've done to make it more usable.

Unfortunately email server maintenance isn't very interesting. It takes away from things that are more cool and useful.

Enhancements

POP Before SMTP — Blog posting on how to enable POP before SMTP for client access without SMTP authentication.
SQLGrey — Zimbra Wiki page on how to integrate SQLGrey with Zimbra. This is the most effective way to cut down on spam currently.