For PM’s on this board, what’s the difference between Outbox and Sent?
Messages you send go to the Outbox. Once the recipient has read the message, it is moved to the Sent.
I have a message I sent to somebody in September 2009 that was never read, still sitting in my Outbox 
Probably because that person logged in just once on that day and never returned…
Ah, ok.
That helps clear things up.
Also, I like that fact that it is still editable while it is in your outbox, since something always changes after I hit send 