There are still plenty of bugs floating around with Apple's Mail program and OS X Server. The discussion boards at Apple are full of people having problems. The main problems seem to be:

• IMAP caching in Mail.app 2 is inconsistent
• Searching "Entire Messages" stops working in Mail.app 2
• Mail.app 2 and Entourage cause "exited, signaled to death by 6" errors on Cyrus IMAP on OS X Server 10.3.9 (and possibly 10.4).

It will be very nice when these problems get fixed. It is tough to tell from Apple's discussion boards if they are really following these issues or not.