Article ID: 113406, created on Mar 2, 2012, last review on May 11, 2014

  • Applies to:
  • Plesk 10.x for Linux
  • Plesk 9.x for Linux/Unix

Symptoms

Mail server may stall or the connection may be broken if an email message with "NULL characters" is received.

You can find messages about the lost connection in the maillog /usr/local/psa/var/log/maillog.

Feb 28 16:10:24 pv14047 postfix/smtpd[2067]: connect from unknown[127.0.0.1]
Feb 28 16:10:24 pv14047 before-queue[3279]: check handlers for addr: mail1@domain.tld
Feb 28 16:10:24 pv14047 before-queue[3279]: check handlers for addr:
mail2@domain.tld
Feb 28 16:10:24 pv14047 before-remote[3280]: check handlers for addr: mail3@domain.tld
Feb 28 16:10:24 pv14047 before-remote[3280]: check handlers for addr: mail4@domain.tld
Feb 28 16:20:24 pv14047 postfix/smtpd[3273]: warning: timeout talking to proxy 127.0.0.1:10025
Feb 28 16:20:24 pv14047 before-queue[3279]: Lost connection.
Feb 28 16:20:24 pv14047 before-remote[3280]: Lost connection.
Feb 28 16:20:24 pv14047 postfix/smtpd[2067]: lost connection after DATA from unknown[127.0.0.1]
Feb 28 16:20:24 pv14047 postfix/smtpd[2067]: disconnect from unknown[127.0.0.1]

Cause

Postfix cannot handle email messages containing NULL characters. Use the following link to read more about this problem: Nulls not being stripped from incoming mail.

Resolution

Add the following line to the postix configuration file main.cf in order to make it possible for postfix to process email containing NULL characters without stalling.
   message_strip_characters = \0

The configuration file is usually located here: /etc/postfix/main.cf.

Restart postfix to apply changes.

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