Postfix stopped working after error: "ct-milter: Too many open files"


2016-11-16 13:24:39 UTC


2017-08-16 16:43:38 UTC


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Postfix stopped working after error: "ct-milter: Too many open files"

Applicable to:

  • Plesk 12.0 for Linux
  • Plesk 11.0 for Linux
  • Plesk 11.5 for Linux


Postfix does not work properly. The following error is shown in the /usr/local/psa/var/log/maillog log:

postfix/smtpd[19989]: NOQUEUE: milter-reject: CONNECT from[]: 451 4.7.1 Service unavailable - try again later; proto=SMTP

The following errors are also present:

ct-milter[2865]: open(/tmp//ctmiWleY2L): Too many open files
postfix/smtpd[19989]: warning: milter unix:/var/spool/postfix/ctmilter/ctmilter.sock: can't read SMFIC_OPTNEG reply packet header: Connection timed out
postfix/smtpd[19989]: warning: milter unix:/var/spool/postfix/ctmilter/ctmilter.sock: read error in initial handshake


The ct-milter daemon has reached the open files limit.


  1. Increase the limit in the ctasd script, adding the following line into the /etc/init.d/ctasd_initd file:

    ULIMIT="-n 4096"   
  2. Check the service status of /etc/init.d/pc-remote . If it has stopped, start it using:

    /etc/init.d/pc-remote start
  3. If the issue persists, disable before-queue mail filters.

    Note: Disabling before-queue mail filters will disable features like Kaspersky, DrWeb checks, DomainKeys, Greylisting, SPF, quota-check, Kaspersky Antivirus, Autoresponder, SpamAssasin and others.

    To disable before-queue mail filters, change the following lines in the /etc/postfix/ file from:

    smtpd_milters = inet:localhost:12768
    non_smtpd_milters = inet:localhost:12768


    #smtpd_milters = inet:localhost:12768
    #non_smtpd_milters = inet:localhost:12768

    Then, restart postfix:

    # /etc/init.d/postfix restart
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