DCF is a useful method for determining whether or not a message is spam. There are two variations of this method. One method (Vipul Razor) exchanges checksums of messages its users has identified as spam. The second method (DCC) exchanges checksums of all messages processed by servers in the network, counting the number of times each checksum has been identified. The DCC method requires a whitelist, as legitimate bulk email will be identified as spam unless the sender is identified in a whitelist.

Both Vipul Razor and DCC are implemented as part of the SpamAssassin package, which is an excellent way to utilize DCF. Using a scoring method rather than rejecting messages based upon DCF eliminates the worry of legitimate messages getting ...

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