Getting the following error in the error log when sending the email 'DSN: User unknown'

Solution Verified - Updated -


  • Getting the User Unknown error when sending an email

  • The following is the error log from /var/log/maillog

Dec  7 23:00:44 prod-db sendmail[14933]: oB870i23014933: from=<>, size=316, class=0, nrcpts=1, msgid=<>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain []
Dec  7 23:00:44 prod-db sendmail[14932]: oB870iKU014932:, ctladdr=root (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30038, relay=[] [], dsn=2.0.0, stat=Sent (oB870i23014933 Message accepted for delivery)
Dec  7 23:00:44 prod-db sendmail[14935]: oB870i23014933: to=<>, ctladdr=<> (0/0), delay=00:00:00, xdelay=00:00:00, mailer=smtp, pri=120316, [], dsn=5.1.1, stat=User unknown
Dec  7 23:00:44 prod-db sendmail[14935]: oB870i23014933: oB870i23014935: DSN: User unknown
Dec  7 23:00:44 prod-db sendmail[14935]: oB870i23014935: to=<>, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=31561, dsn=2.0.0, stat=Sent


  • Red Hat Enterprise Linux 5
  • Red Hat Enterprise Linux 6
  • Sendmail

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