Outlook 2011 for Mac continues to send emails that aren’t there

My outlook continues to try and send 7 emails over and over again. I have no idea what these emails are, they aren't in my outbox, and I cannot figure out how to delete whatever files its trying to send. I believe they were files that were too large at some point and I can pull up the diagnostic box that says email too large cannot send, but I cannot figure out how to delete those message from wherever they are being stored.