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SPAM Playbook: Spam-filtering Tools

Appropriate Filtering

The only way to eliminate the costs is to eliminate spam. You can accomplish this typically by implementing one or more e-mail filters. Many options exist, though not all are viable for every organization or user. For instance, a lawyer might be required to keep a copy of every e-mail he or she receives. Further, some filters operate best at the edge, while others require end-user manipulation.

Broad-based edge filters provide the biggest bang for the buck, in that they are designed to keep junk mail from ever being received by your server. The cost savings decrease as filters move closer to the user--more bandwidth, storage and processing capacity are needed when unfiltered mail travels further into your enterprise. Rejecting mail at the edge of the network also means you don't have to generate delivery-failure notification messages (the sending system is responsible), which alleviates problems associated with junk e-mail using a forged sender address.

On the other hand, a customized user-based filter that examines each message in context can keep mailboxes remarkably clean with a small amount of false positives, but it uses the most system resources and causes the greatest productivity losses because it needs more administration.

Tiered Filtering

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