http://the-barracuda-spam.blogspot.com/

A spam filter is a web-based program which helps to prevent spam e-
mail from entering your inbox. Password filter, blacklist and,
whitelist filters, challenge/response filter, rules-based filter,
community-based filter, and adaptive/Bayesian filter are among the
common types of spam filters used nowadays.

Password filters are the basic form of filtering commonly used. These
block e-mails without password in the subject line. E-mails containing
a pre-set password in the subject line alone are accepted. But, this
filter might sometimes block.....read more at :

http://the-barracuda-spam.blogspot.com

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