Anti-Spam SMTP Proxy

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Anti-Spam SMTP Proxy
Original author(s)John Hanna
Developer(s)Thomas Eckardt in association with the ASSP community
Stable release
2.8.1(23131) / May 11, 2023; 18 months ago (2023-05-11)
Preview release
2.8.2(23136) / May 16, 2023; 18 months ago (2023-05-16)
Written in
GNU General Public License
Websiteassp.sourceforge.net

The Anti-Spam SMTP Proxy (ASSP) is an

transparent SMTP proxy
server.

Features

Some ASSP's features are:

  • Hidden Markov Model spam filtering
  • Bayesian spam filtering
  • whitelisting
  • Penalty Box (PB) trapping
  • DNSBL
    /RBL (Realtime Blackhole Listing)
  • URIBL (Uniform Resource Identifier Black Listing)
  • Multi-level SPF (Sender Policy Framework) validation and blocking
  • DKIM signing and validation
  • DMARC validation and reporting
  • SRS (Sender Rewriting Scheme) fix-up
  • Session Delaying/Greylisting and connection response delaying
  • Sender validation and recipient validation
  • Multi-level attachment blocking (based on block lists or allow lists or content based executable blocking)
  • As well as multiple RFC validation mechanisms.
  • Multi-threaded
    (Since version 2.x)
  • Platform independent (Written in Perl)

See also

  • Transparent SMTP proxy
  • SpamAssassin
    , popular open source spam filtering that uses razor and other techniques to detect spam.
  • Qpsmtpd, a similar project