Quote:
I have a message stuck in my outbox
That means you sent a PM to someone and they have not yet opened your message. Once they have, the message will automatically move from your Outbox to your Sentbox.
If you really want to delete the Outbox message (which means that person will never read the message), put a check mark in the box to the far right of it and from the drop-down box at the bottom, choose "Delete Marked" and it will leave your Outbox and the intended recipient will not see it.