Exchange Newbie

Someone attempted to e-mail a file attachment that was 22MB in size. I suspect that because of that, it is “clogging” up the Exchange service. Our e-mail keeps going down, and I have zero experience with Exchange. I would I purge the files due tobe sent in Exchange. It is version 5.5 running on NT 4 with SP6. If anyone can lend any insight, I would be most grateful. Thanks in advance.