Kan ikke sende emails

Hver gang jeg prøver at sende en mail via Outlook får jeg følgende besked fra "System Administrator" inden jeg når at Send/modtag'e:

Your message did not reach some or all of the intended recipients.

      Subject:    emne
      Sent:    10-09-2003 23:12

The following recipient(s) could not be reached:

      'email@domain.dk' on 10-09-2003 23:12
            550 relaying mail to email@domain.dk is not allowed