I used to run all my own stuff, but when my children came along, I didn't want to spend all my time chasing issues with servers.
Look the Fastmail guys up. If anyone is doing email correctly, it's Rob, Bron, and the guys at Fastmail. They actually write some of the code for the Cyrus IMAP server, so if you were in doubt as to how talented these guys are, don't fear. I would now NOT trust my email to anyone else. They are that good. Yes, I know, I'm some random guy on the Internet, but I'm an IT guy, which in itself says nothing, but I'm nothing if not extremely picky about my own IT. These guys can fix any issues you may have and probably give you some awesome suggestions. They are approachable, something you will never get from any other company. They are based in Melbourne, Australia, but use NYI here in the US. Worth a call if you value good service and top-notch know-how from guys who know email better than anyone else I'm aware of. They routinely post in the Email Discussions Web site forum.