Cannot send message: unknown user


2016-11-16 13:12:07 UTC


2017-08-08 13:28:15 UTC


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Cannot send message: unknown user

Applicable to:

  • Plesk 12.0 for Linux


  • Trying to send a message from webmail, the message bounces:

    Sep 20 12:08:48 www postfix/qmgr[13769]: 9DF3D8136E: from=<test@example.tld>, size=901, nrcpt=1 (queue active)
    Sep 20 12:08:48 www postfix/local[14235]: 9DF3D8136E: to=<user@domain.tld>, relay=local, delay=0.11, delays=0.1/0.01/0/0.01, dsn=5.1.1, status=bounced (unknown user: "user@domain.tld")
  • Both domains are located on that Plesk server

Cause file was customized in a bad way, it contains destination domain:

mydestination =, localhost, localhost.localdomain, domain.tld

For postfix it means to use $local_transport mail delivery transport. The SMTP server validates recipient addresses with $local_recipient_maps and rejects non-existent recipients. And there is no such a user in local_recipient_maps


Remove domain from mydestination list.

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