SnertSoft: We Serve Your Server


«An SMTP Filtering Proxy»


Where Barricade MX fits in on your mail system.
The Big Picture

smtpf sits in front of one or more MTAs on SMTP port 25. It acts as a proxy, filtering and forwarding mail to one or more MTAs, which can be on the same machine or different machines.

By using an independent SMTP pre-filter in the form of a proxy we avoid portability differences and limitations of MTA extension methods (milters, plugins, rule sets, etc.) and tighly couple & integrate tests to improve performance & message throughput.

smtpf supports a variety of well blended anti-spam filtering techniques that can be individually enabled or disabled according to the rigours of the postmaster's local filtering policy. Some of the tests available are:

  • Avast!, ClamAV, and F-Prot anti-virus support
  • "Client-Is-MX" heuristics for PTR and IP in name checks
  • Concurrent connection limits
  • Connection rate throttling
  • DNS real-time black, grey, and white lists
  • Enhanced grey-listing
  • HELO claims to be us
  • Local black/white list by IP, host name, domain, MAIL, RCPT
  • Message limit & size controls
  • Recipient verification using call-ahead
  • Sender verification using call-back
  • SIQ protocol support for reputation services
  • SMTP command & greet pause
  • SpamAssassin anti-spam support
  • SPF Classic support
  • Tar pitting negative SMTP responses
  • URI blacklist test of PTR, HELO, and MAIL
  • URI blacklist testing of message content
  • White wash & backscatter prevention with EMEW

Another feature of smtpf is the multicast / unicast cache, which provides a fast, simple, and efficient means to share cache updates across multiple machines on the same network segment or to a set of remote hosts. The multicast / unicast cache use a broadcast-and-correct model and support IPv4 & IPv6.

dastardly villians since 1 November 2006