Premium Outgoing Antispam: Mail delivery fails: 451 4.7.1 Service unavailable - try again later

Created:

2016-11-16 12:51:55 UTC

Modified:

2017-04-24 11:20:19 UTC

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Premium Outgoing Antispam: Mail delivery fails: 451 4.7.1 Service unavailable - try again later

Applicable to:

  • Plesk 12.5 for Linux
  • Plesk 11.0 for Linux
  • Plesk 11.5 for Linux
  • Plesk 12.0 for Linux
  • Plesk 10.x and below for Linux

Symptoms

Mail delivery does not work. Messages like the following are logged into '/usr/local/psa/var/log/maillog' :

postfix/smtpd[22697]: warning: connect to Milter service inet:localhost:12768: Connection refused
postfix/smtpd[22697]: NOQUEUE: milter-reject: CONNECT from unknown[1.2.3.4]: 451 4.7.1 Service unavailable - try again later; proto=SMTP

Premium Outgoing Antispam is installed on the server, or was installed and later removed.

Cause

Premium Outgoing Antispam uses a special milter service that should listen on port 12768.Additionally, the issue may be caused by one of the following mail handlers, which is working through the postfix milter:

greylisting
SPF
quota-check
Kaspersky Antivirus
Dr. Web
Autoresponder
SpamAssasin
dk_check (domain keys)
maillisting

There are two possible causes of the issue with Outgoing Antispam:

  1. The CTmilter service has crashed
  2. Premium Outgoing Antispam has been disabled, but milter is still present in the Postfix configuration:
    # cat /etc/postfix/main.cf | grep -i milters
    smtpd_milters = inet:127.0.0.1:12768 unix:/ctmilter/ctmilter.sock
    non_smtpd_milters = unix:/ctmilter/ctmilter.sock

Resolution

Make sure that you have Premium Outgoing Antispam installed on a server as this article applies to only servers with installed Premium Outgoing Antispam. Go to Extensions to check if you have it installed:

alttext

If it is not installed, visit:

#213407889 "451 4.7.1 Service Unavailable - Try Again Later" Messages in the Maillog

Below instructions are only for servers with Premium Outgoing Antispam installed:

  1. Start the outgoing antispam milter service or reinstall it if required:
    # /etc/init.d/ctasd_initd start
    # /etc/init.d/ctmilter_initd start

Check the following article, which may include information related to the failure: # 213415889

OR

Check whether the psa-pc-remote service is started.

    # service pc-remote status
  1. Default milter configuration without Premium Outgoing Antispam should be the following:

  2. on Debian-based OS:

        # cat /etc/postfix/main.cf | grep -i milters
    smtpd_milters = inet:127.0.0.1:12768
    non_smtpd_milters =
  3. on RedHat-based OS:

        # cat /etc/postfix/main.cf | grep -i milters
    smtpd_milters = , inet:127.0.0.1:12768
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