by David Grimes » Oct 28, 2012 10:13 am
Just to elaborate a little, the sent folder contains all messages that you have sent, at least until you reach the limit on the number of stored messages then they will be replaced one at a time as you send new messages.
The outbox folder contains sent messages that have not been read by the person receiving the message. This folder is really just like a delivery confirmation, you will know someone has read your message when it disappears from this folder.