MSN Outlook program--sending phantom emails

I have set up my Hotmail Account to use my Microsoft Outlook application. This has been fine for a few years, but in the past several weeks, I've noticed a distracting indicator at the bottom of my screen, showing a large number of emails that supposedly are currently being "sent." I say "supposedly" because there are NO emails in my outbox when this happens, and because the number it says it is 'sending' are hundreds and sometimes thousands (E.G., by the time i notice it, it might say, "sending message 2,349 of 2,457"). The only way i can get it to stop is by shutting down Outlook, then logging in again).

Apparently, it is spontaneously "sending" phantom emails? emails from my deleted files? emails from my already sent files?? and where it is "sending" them?

Has anyone had this experience? and do you know how to stop this from happening?