Clapf is a high performance open source email content filter application. It includes a statistical (inverse chi-square) antispam module, support for anti-virus products, a nice web based gui (including a spam quarantine) written in PHP.
It supports virtual users, URL blacklists, whitelists, LDAP directories, policy groups, minefield, and many more.
clapf can be used as an after queue content filter with Postfix (including as an appliance) and Exim
.clapf also can work as an appliance before Exchange or virtually any SMTP server.
For larger installations with multiple spam filtering nodes, check out the advanced layout section in the docs.
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