Spam. I use a black list and a personal kill list. My home on the net, slowass.net, is sh*tlisted with the very services that I use to avoid spam myself. My sendmail hasn't been an open relay in years, since the time before time when spam didn't exist and sendmail just came open. No, the reason I'm sh*tlisted is because another user "on the same subnet" is a spammer. Living in a non linear world, if X cures Y, it doesn't always follow that more X will cure Y. For instance, its possible to overdose on pain killer and get a nasty headache. By fighting spam too aggressively, you're risking tickling the non-linear nature of the system. Technology, scanning, reporting, honey pots, and good public relations are all important. Punishing innocents and bad PR should be avoided. Sh*tlisting an entire subnet because of one spammer is like throwing out the baby with the bath water. You've shut up one spammer, but you've got 253 people who are confused and upset as to why they can't mail their friends, and they don't blame the spammers, they blame the anti-spam witch hunt. A friend of mine implemented an interesting little hack: if you aren't on his buddy list and you email him, you get your message back with a trivia question. Answer the trivia question, and your on the buddy list, and your reply goes through. I'm thinking about doing real-time testing for open relays as part of my local mail scripting. A few hours hack, if I can scrape it up. Honeypots that trap known spammers and open relays have proven very effective. With all of these solutions, damning entire subdomains to hell seems unneeded, too aggressive, and counter effective.