Outgoing should be a Temp area till the message is confirmed sent to recipient, then its moved to sent. At least that is what I have deduced from my past messages.
My Commander has Small Feet "You're doing it wrong". No, we are having Fun OUR way. ~-~The A-Team Board ~-~ 12 year olds tearing around the woods on dirt bikes have LESS FUN than we do!
What Loriath said. Messages stay in the outbox until at least one of the recipients has opened it. Then it is moved to the sent folder. As long as no recipient has opened it and it is still in the outbox, you can still edit or cancel the message. Once in the sent folder this is no more possible.
If you look at this http://screencast.com/t/nqfBwwa1 you will see an extract of my 'outbox' All these messages are shown as sent, this is what is confusing me as my 'sent' folder holds different messages, also shown as sent.