I did get paged from work with a warning that CPU usage on our mail server was a little higher than it should be. Everything was working fine, but after an hour of it being that high I biked down to check it out. Well apparently one of customers must have ticked off some italian guy because this guy sent about 300,000 (yes!) emails to this guy.
Essentially they said "How are you going to get all this email" and then some random text. The guys mailbox filled up at 2500 emails though and the rest just bounced. But it takes a while for the server to generate that many bounces. Should be going now though.