edgesync '5.1.1 User unknown' – Posted on May 7, 2012 by dpejic After resync HUB with the Edge Server, users are not able to receive mail and sender get NDR ” #5.0.0 smtp; 5.1.0 – Unknown address error 550-‘5.1.1 User unknown’ (delivery attempts: 0)> #SMTP# ” . In star-edgesynchronization command i got also “AcceptedDomainStatus: NotSynchronized” For me, the solution was very simple (after an hour to find a solution 🙂 ), i have disable recipient filtering agent on my Edge server and the mail flow are starting to work. 🙂