Understand How Various Spam Software Works

"When considering how to protect your mail system from spam, you'll find that there are way too many choices in the marketplace to be able to possibly evaluate them all. Since each solution handles spam differently, it's important to understand the various methods by which spam filters do their deeds. There are four major types of spam technology available: Bayesian, Whitelist and blacklist, Content-based, Challenge/response. Each is discussed in the article." Source: TechRepublic.com