Mail won't stop sending Message

I tried to send an email with a video that was 38M, which is apparently too large. So my mailbox is stuck in this loop of trying to send the mail with too large of an attachment despite not being able to succeed due to, I guess, technical reasons. How do I get my Mail app to break this loop? My "Recovered Messages (Yahoo)" in my "On My Mac" folder keep multiplying by the minute. Please provide me some advice with which I can stop this incessant loop.

-Carter