Depending on how egregious the spammer is, I'll just add their IP / netblock to my blacklist, which refuses ALL mail from that IP space. Haven't seen an instance yet where I've had to roll one of those changes back because I accidentally got a false positive.
Combine that with things like SBLs, Reputation scores, and other anti-spam methods, and I get upwards of 90% of my volume being refused.
Biting the hand that feeds IT
