I have started a spamhole.
There are some excellent spam filtering programs out there. However, there are some simple brute force, satisfying steps I can take to reduce spam at the mail server. I can ban ip numbers. I can ban isp domains.
I don't know anybody in Japan. Nobody in Japan is likely to send me mail I want to read. However, some spammers in Japan used ne.jp to offer me viagara. Shut that sucker right off. I have domains shut off in Argentina, Brazil, Mexico, China, Taiwan and Huland. I don't really know where Huland is, but their domain suffix is .hu. Interbusiness.it and doneasy.com alone account for hundreds of spams on my server; along with ne.jp.
Every morning, I see what spams have survived as far as my mail reader. I look at the headers and decide if I want to ban a host, a network or a whole domain. I make a few entries in my ever growing shit list.
Every hour, there's a dump from spammers using email lists that must be ten years old. They're trying to spam users from an old modem BBS who don't have accounts. Every time my server tries to send out hundreds of nouser notices to bogus servers; mail queues fill up and bounce notices get bounced. There's a chance somebody has just made a mistake with my email address and needs a bounce to get them to double check. Well, tough gnoogies. From now on, every bad address is just dumped into the byte-hole.