I told a nigerian no, and now he is using a botnet

Ok, so a nigerian scammer tried getting me to send him money and I told him no and if he ever contacted me I would contact the FBI. I didn't realize until after the email it attached my signature to it so he saw my site address. I know its him because the first IP was the same as where his email came from. I crashed the site intentionally hoping it would stop. The second I brought it back up it started again. Although I know he won't get in because he isn't using the right username, its really annoying because I have received 800 emails today and he is about to use up my daily email quota. I can't just ban the IP either because it is multiple. What should I do?