Error or Reply with "User unknown in virtual alias table"

[rockbd]

Recently some of my user are getting following error"

Reporting-MTA: dns; MyIronPort.MyDomain.com

Final-Recipient: rfc822;x.y@abc.com
Action: failed
Status: 5.0.0 (permanent failure)
Remote-MTA: dns; [1.7.21.8]
Diagnostic-Code: smtp; 5.1.0 - Unknown address error 550-'5.1.1 <x.y@abc.com>: Recipient address rejected: User unknown in virtual alias table' (delivery attempts: 0)

I think it is nothing wrong with my IronPort configuration. Am i right? If i am right then what might be the problem. any suggestion.

[Libin Varghese]

Is this an incoming or outgoing email?

What does the message tracking or mail logs on the ESA show?

Any error shown for the DCID would suggest the destination server rejected the email address you tried to deliver the email to. 

Regards 

Libin Varghese 

[rockbd]

It is in outgoing mail.

I didn't check the mail log? i will check it and inform me.

My query why this message is rejected with this error?

[Libin Varghese]

Well based on the wordings of the errors the recipient does not exist on the destination server and hence the email was rejected.

Regards,

Libin Varghese