#rev 2018-11-22 maegger
#rev 2020-09-04 maegger

= 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.
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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:
  * [[http://www.postfix.org/POSTSCREEN_README.html#perm_white_black|permanent white-/blacklist tests]]
  * [[http://www.postfix.org/POSTSCREEN_README.html#temp_white|temporary white-/blacklist tests]]
  * [[http://www.postfix.org/POSTSCREEN_README.html#white_veto|MX policy tests]]
 * In the simple test phase, postscreen does:
  * [[http://www.postfix.org/POSTSCREEN_README.html#pregreet|Pregreet tests]]
  * [[http://www.postfix.org/POSTSCREEN_README.html#dnsbl|DNS White/blacklist test]]
 * In the deep test phase, postscreen does:
  * [[http://www.postfix.org/POSTSCREEN_README.html#pipelining|Command pipelining test]]
  * [[http://www.postfix.org/POSTSCREEN_README.html#non_smtp|Non-SMTP command test]]
  * [[http://www.postfix.org/POSTSCREEN_README.html#barelf|Bare newline test]]
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[[CategoryMAIL]]