Couldn't agree more and have considered building something similar in the past. Seems like such a gigantic project though.
I'd probably host my own mail if it were a matter of installing one server, hooking it up to a database (much prefer the idea of storing email in a database than mbox files) and giving it a few details. Even better if it came with a simple web interface for viewing email and for configuring.
I've set up mail servers in the past but I've always been left a bit uneasy, as if there's a possibility I've not quite set it up right.