Today, numerous companies offer anti-spam solutions. Most techniques to block spam (unsolicited and unwanted email) focus on either attempting to identify the sender or analyzing the e-mail content or both. When successful, anti-spam solutions, on average, block about 80% of the spam they filter – some a little better; others much less so. And often there is a tradeoff between the level of spam blocked and the level of legitimate email delivered –a tradeoff most users find unacceptable.
By focusing primarily on the symptoms of spam (analyzing the sender and/or the email message), these solutions depend on characteristics over which spammers have complete control. Thus, at best, these solutions are only as good as yesterday's spammer profile and will always be a few steps behind the latest and greatest ploys in the spammer arsenal. Anti-spammer efforts to defeat spam become a never-ending cat and mouse game over which these anti-spam strategies clearly can never expect to ultimately declare victory.