Hello, It seems that no one has responded to you in some time.
My name is XXXXX XXXXX I would like to assist you with this issue.
What we want to try and do, is first tell outlook to go offline..
And then, we want to try and delete the message while outlook is offline, or else move the message from the sent folder into another folder, such as drafts.. Where we can then delete it.. ( or at least get it out of the folder)
Once deleted we want to take outlook back online, and then you should be back to normal operation.
The page below covers the process with more detail.
If you get stuck or have any questions, please let me know.
I strive to provide great service, and greatly appreciate a rating of excellent below when you are satisfied.. I always answer follow up questions.
Senior Technician and Network Switching Systems Operator / Maintainer.