Usually. I've found it easier just to put everything through a Gmail account (Google Apps in the Workplace, more exactly). The Google spam filter is absolutely awesome and the blacklist feature always works. If you need help configuring this, give me a shout.

Filtering by IP address doesn't work much: most spam is forwarded through a huge army of computers that have been compromised by "worm" programs. Most of these don't even know they're sending spam, you'll never get a significant portion of them into your spam filter. There are 2 solutions I use which catch about 98% of it: Spam Bayes runs on your local computer, its free (just google the name). I also use a 3rd party mail server (www.webmail.us) to pre-filter everything that comes to my mail domain. If you don't have a domain, and don't mind using gmail.com, Google's gmail service seems to be pretty effective against spam. ~~~~~~~~~~~ EDIT #1 There is no fixed rule you're going to get developed which is going to make a significant difference. Spammers have become too sophisticated for that, I'm afraid. The mail server you choose has a big effect: they can be configured in ways which help prevent spam by enforcing certain protocol constraints, and many of them now have adaptive filters (like Spam Bayes or Spam Assassin). I've had the same e-mail address for many years, I think its in just about every spam database on the planet. Between the webmail.us filter and my own Spam Bayes, they catch several hundred spam a day and I only have to purge a few manually. Its an acceptable situation which doesn't require me to change my address (something I'm loathe to do). But any filter has to use adaptive techniques to deal with all the ambiguities and new methods used by spammers.