Take a look here, it may help:
http://www.howto-outlook.com/Faq/mes...ckinoutbox.htm

"Bottle" wrote in message
ups.com...
I have an email that is stuck in the outbox. Message is probably to
big to send. Any idea how to get rid of it? Tried deleting it, but
Outlook keeps telling me it is in the process of sending the message.