I use XMailServer at home, I think it is easy to configure even thought there are tons of files to tweak to make it work, it's pretty good and fast and in general quite reliable.
Version 1.24 is available now. It fixes some bugs from older versions, and runs just fine.
But what I like the most right now is the glst tool. "glst" stands for Greylisting which is a relatively recent way to eliminate 99.9% of the spam you get in your mailbox. For that one too, you need some setup. At this time, the tool come raw I'd say. So I added the list of servers listed on the greylist which are known to fail badly with the Greylisting functionality (among those: AOL, he! he! How surprising!)
I made some changes to the configuration file and a small patch to the parser for the configuration file to ensure that comments are properly taken in account as comments (introduced with a '#' character.) Since it is GPL, I could keep these changes to myself, but there is no reason I wouldn't share those.
The additions to the configuration file is a list of xnet entries to authorize these networks to send emails no matter what (a Whitelist if you wish. They are not themselves spamming people anyway. Watchout, this includes a list of possible local networks; you should comment out those you do not use in your organization.