Postfix keeps stopping, preventing the sending of mail.

Refers to:

  • Plesk for Linux

Created:

2016-11-16 13:25:18 UTC

Modified:

2016-12-21 20:40:39 UTC

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Postfix keeps stopping, preventing the sending of mail.

Symptoms

Postfix keeps stopping, preventing the sending of mail. Mail received with a significant delay.

' maillog ' file contain a lot of messages like "lost connection after CONNECT" and the following warning message:

Oct 19 04:49:52 mail postfix/master[10149]: warning: service "smtp" (25) has reached its process limit "100": new clients may experience noticeable delays
Oct 19 04:49:52 mail postfix/master[10149]: warning: to avoid this condition, increase the process count in master.cf or reduce the service time per client
Oct 19 04:49:52 mail postfix/master[10149]: warning: see http://www.postfix.org/STRESS_README.html for examples of stress-adapting configuration settings

Cause

Mail server overloaded and switched to stress mode. Postfix version 2.5 introduces automatic stress-adaptive behaviour. It works as follows. When a "public" network service such as the SMTP server runs into an "all server ports are busy" condition, the Postfix master daemon logs a warning, restarts the service (without interrupting existing network sessions), and runs the service with " -o stress=yes " on the server process command line.

Resolution

Increase ' default_process_limit ' in ' /etc/postfix/main.cf ' and fine tune other performance/stress related configuration settings in postfix by following stress configuration directives explanations described in "Postfix Stress-Dependent Configuration"

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