Wow, Zimbra (and the team that's created it) is awesome. Went on my tired, old Debian laptop (512 MB ram) without a hitch; I'm especially impressed with how easy it is to manage many server aspects of the server from the web interface.
I was concerned that configuring a small Bind nameserver (for local name resolution within my network) would be tough but the DNS in a nutshell was clear and easy to follow. I was also worried that my webserver would interfere with Zimbra, but again my questions were answered in the forum (specifically, here). And though this is my first post on the forums, over the course of a Saturday I spend here, I noticed that forum questions were most often responded to quickly, kindly, and throughly... many times by the developers themseleves! This is one of the friendliest and most helpful program documentation repositories I've come across.
I've wanted to have a mail server for awhile, but was too intimidated by the complexity of configuring postfix (or others for that matter) to use a database. With all the hardwork the Zimbra team has devoted to making this an awesome product, not only do I have a mail server, but calendaring, contact management, client software freedom, etc. Unbelievable!
Thanks again! Next up, Zimbra in Xen.