Domain Keys are not signing email even when the setting is enabled server-wide


2016-11-16 13:08:18 UTC


2017-08-16 16:31:55 UTC


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Domain Keys are not signing email even when the setting is enabled server-wide

Applicable to:

  • Plesk 12.5 for Linux
  • Plesk 11.x for Linux
  • Plesk 12.0 for Linux


Domain keys are not signing outgoing emails.

According to Domain Keys Reputation emails are NOT signed.

Please note: DKIM is not supported by Plesk, only Domains Keys are supported.


The issue might be caused due to following reasons;

  1. TXT records are not valid.

  2. DKIM and DomainKeys are installed and sharing the same Selector name

  3. Domain keys are not valid. Verify the same using

  4. Broken dd52-domainkeys handler.

  5. Misconfiguration in /etc/postfix/ file

    # grep milters /etc/postfix/
    smtpd_milters = ,,,
    non_smtpd_milters = ,,,,,


To solve the issue do the following:

  1. Check that the option "Use DomainKeys spam protection system to sign outgoing email messages" is enabled both in server-wide and domain levels.

    Go Home > Tools & Settings > Server-Wide Mail Settings in DomainKeys spam protection section for server-wide.

    Go Home > Subscriptions > SUBSCRIPTION_NAME > DOMAIN_NAME > Mail > Mail Settings for domain level

Try to re-enable the option by unchecking/checking the settings.

  1. If DKIM is installed:

    • make sure that Selector name in /etc/opendkim.conf differs from default

    • default._domainkey.domain.tld do not have DKIM specific signature like v=DKIM1; k=rsa;

  2. Run mchk utility utility to fix the issue with broken handler:

  3. If misconfiguration of Postfix causes the issue, edit /etc/postfix/ as follows:

    # grep milters /etc/postfix/
    smtpd_milters = , inet:
    non_smtpd_milters = , inet:

    comment following lines:

    #milter_connect_macros = j {daemon_name} {client_connections} {client_addr}
    #milter_connect_macros = j {daemon_name}
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