Article ID: 124056, created on Dec 27, 2014, last review on Jun 6, 2016

  • Applies to:
  • Plesk 12.5 for Linux
  • Plesk 12.0 for Linux
  • Plesk 11.0 for Linux
  • Plesk 11.5 for Linux


  1. Mail delivery does not work. The following messages are logged into /usr/local/psa/var/log/maillog:

    /usr/lib/plesk-9.0/psa-pc-remote[1759]: handlers_stderr: DEFER
    spf filter[1360]: Error code: (26) DNS lookup failure
    /usr/lib/plesk-9.0/psa-pc-remote[1759]: DEFER during call 'spf' handler
    spf filter[1360]: SPF result: tempfail
    postfix/cleanup[29479]: 694B91E328E: milter-reject: END-OF-MESSAGE from[]: 4.7.1 Service unavailable - try again later; 


    Handlers Filter before-queue for qmail started ...
    spf filter[8808]: Starting spf filter...
    spf filter[8808]: Error code: (26) DNS lookup failure
    spf filter[8808]: SPF result: tempfail
    handlers_stderr: DEFER
    DEFER during call 'spf' handler
  2. SPF local rules are set as follows:

    # /usr/local/psa/bin/mailserver -i spf
    SPF local rules:

    or in Plesk GUI: Tools and Settings > Mail Server Settings

  3. is not available:

    # ping
    ping: unknown host


SPF checker "" does not work anymore


Disable local rules:

  1. Open Tools and Settings > Mail Server Settings

  2. Remove specified domain in SPF local rules

Additional information

SPF local rules are applied by the spam filter before the SPF check is actually done by the mail server. For more information on SPF rules, visit

Search Words

unknown host

Error code: (26) DNS lookup failure

(26) DNS lookup failure

SPF result tempfail


DEFER during call spf handler

DNS lookup failure

Email are not being delivered

END-OF-MESSAGE service unavailable

Service unavailable - try again later

spf deferred

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