Thought you could escape spam with smart email filters? Think again. A Georgia school district has learned the hard way that it doesn't pay to rely on those filters completely. A Cobb County School District spam filter may have cost the district $250K when it blocked email about lower telephone services bid from a contractor.
District officials say they have no way to retrieve the message. Spam filters that work at the gateway level often discard the messages out of hand, and thus must be carefully tuned to not report any good non-spam email ("ham") as being spam.
Some filters, such as the one built into Microsoft Outlook or Google's GMail, redirect likely spam to a folder and hold it for a few days. This gives you the chance to review what the filter did, and help train it on what is and isn't spam. However you would need to check your Junk E-mail/Spam folder regularly (at least once a week) to check for mistakes, and most people don't bother.
A number of good open source spam filters are available such as SpamAssassin and SpamBayes. Identifying and filtering spam is something of an arms race - as the filters get smarter the spammers get more devious. Understanding how your filters work, their limitations, and what is expected of you can help keep your innocent email from becoming a casualty of war.
Source: eSchool News