Kill Spammers

Speaking of pre-emption, some spammer has gone and done what I dreaded for awhile: He (or she) is simply making up addresses at my domain and sending more or less the same email several times per hour. The only saving grace I can see so far is the sender seems to be resource constrained on how frequently the messages can be sent, or something like that, because I’ve only received about 40 in the 10 hours since they first arrived.