I'm updating my old Mail library. It was kinda musty and prone to failure due to my inexplicable idiocy (read "newbieness").
Among the features slated are auto-pruning of old mails, a more robust frame-work, and general removal of anything resembling "usr" =P
The other features have yet to be decided, because they're thought of by you! That's right, I want to know what you want to see in a customizable in-game mail system.