Crazy hard drive-eating Mail problem

I recently (and very stupidly) tried to email a large number of very large files to a friend down the hall in my dorm. There were nine files, about 7MB each. Yes, it was dumb to try and email them, and even dumber to try and email them all in the same message... but I didn't know it would cause a constant (and so far, unfixable) problem.



Quite obviously, I got a message telling me that the mail was undeliverable. It contained both a message saying that it was too big, and a quote of my message, including all those big files. So it took a while to download, even with broadband.



I deleted the message after it came to me, but immediately afterwards, it reappeared. This happened a few times until I tried replying to the message (probably useless). After that, I knew it wasn't sending me multiple messages because each time I got the message, it had a little "reply" arrow next to it.



I also noticed that the amount of room on my hard drive went from 1.7GB to about 900MB. I looked and looked for the files that were taking up all this room, but I couldn't find anything. There was only one copy of each file I sent, not multiple ones.



So how do I prevent from getting these messages, and how do I free up all the hard drive space? It also slows down Mail a lot.