Article ID: 123375, created on Nov 2, 2014, last review on Nov 2, 2014

  • Applies to:
  • Plesk 12.0 for Linux


Postfix keeps stopping, preventing the sending of mail. 'maillog' file I contains 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 or reduce the service time per client
Oct 19 04:49:52 mail postfix/master[10149]: warning: see for examples of stress-adapting configuration settings


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.


Increase 'default_process_limit' in '/etc/postfix/' 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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