for some reason i am not able to receive email sent from my server.

It occurs only on 1 particular user. But as far as i can see
the user exists and all looks okay...

Other tests, sending emails to another user (from the same server to it self) doesn't run in to problems.

the /var/log/maillog says:

p2SAG7w8005691: [email protected], delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31527, relay=[] [], dsn=5.1.1, stat=User unknown

what am i missing?