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
2.6.3(19169) / June 18, 2019; 23 months ago (2019-06-18)
Preview release
2.6.4(19175) / June 24, 2019; 23 months ago (2019-06-24)
Written inPerl
Operating systemCross-platform
TypeEmail spam filter
LicenseGNU General Public License

The Anti-Spam SMTP Proxy (ASSP) is an open-source, Perl based, platform-independent transparent SMTP proxy server.


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

Edited: 2021-06-18 14:32:04