You can check your old sent messages by simply going to private messages and look in the "folder control" box up at the top center of the screen. If you look in this box you will see the phrase "jump to folder:" with a draw box right under it. Just click on the down arrow and you will have two choices, inbox and sent items. Just select "sent items" and hit the "go" button! It will bring up whatever messages you have sent, when and also who you sent them too.
Hope this does it
Mitch