Postscreen

The Postfix postscreen server provides additional protection against mail server overload. One postscreen process handles multiple inbound SMTP connections, and decides which clients may talk to a Postfix SMTP server process. By keeping spambots away, postscreen leaves more SMTP server processes available for legitimate clients, and delays the onset of server overload conditions.

Postscreen is part of postfix since 20th January 2011 (since version 2.8.0) and has been productive on our mailserver since 22th June 2011.

• postscreen is one process wich every client connects to
• postscreen then decides if the connection is legit (and overgives it to a real smtpd process) or if the connection should be dropped.

• postscreen does some quick, simple and deep tests to decide if the sender is good or bad.

• In the quick test phase, postscreen does:

  • permanent white-/blacklist tests

  • temporary white-/blacklist tests

  • MX policy tests

• In the simple test phase, postscreen does:

  • Pregreet tests

  • DNS White/blacklist test

• In the deep test phase, postscreen does:

  • Command pipelining test

  • Non-SMTP command test

  • Bare newline test

CategoryMAIL