[HUB] Mail delivery fails: 451 4.7.1 Service unavailable


2017-05-16 11:10:28 UTC


2017-08-08 13:25:48 UTC


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[HUB] Mail delivery fails: 451 4.7.1 Service unavailable

Applicable to:

  • Plesk for Linux


Mail delivery fails with the message in /var/log/maillog:

451 4.7.1 Service unavailable - try again later


Mail configuration is broken or greylisting filtered the address.


Note: After every step, the issue persistence should be verified.

  1. Use automatic repair tool to check and repair mail configuration:

    # /usr/local/psa/admin/sbin/mchk
  2. Check Postfix milter settings to make sure that it is configured properly and no other service added to it. Default configuration:
    # grep -i milter /etc/postfix/main.cf
    smtpd_milters = , inet:

    Make sure that pc-remote service is running and listening 12768 port:
    # service pc-remote status
    # netstat -ntpl | grep pc-remote
    tcp 0 0* LISTEN 117/psa-pc-remote

    Restart service if it is running.
  3. Make sure that it is enough server's resources:
    # free -m
    # df -h
  4. Disable greylisting service in Tools and Settings > Spam Filter > Switch on server-wide greylisting spam protection
  5. If the issue persists, reproduce the issue and check the error in /var/log/maillog and search for a solution in Plesk Knowledge Base :

Known Issues

Related HUBs

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