Just tried sending mail to that address and get the following 'Undelivered Mail Returned to Sender' message. Any bright ideas:
This is the mail system at host mdfmta004.tbr.inty.net.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<mike@xyz.com>: host mail.xyz.com[12.34.56.789]
said: 550 5.1.1 <mike@xyz.com>: Recipient address rejected:
User unknown in virtual alias table (in reply to RCPT TO command)
Reporting-MTA: dns; mdfmta004.tbr.inty.net
X-Postfix-Queue-ID: C5DA7A0C07F
X-Postfix-Sender: rfc822; mike@abc.com
Arrival-Date: Wed, 19 Sep 2012 22:48:44 +0100 (BST)
Final-Recipient: rfc822; mike@xyz.com
Original-Recipient: rfc822;mike@xyz.com
Action: failed
Status: 5.1.1
Remote-MTA: dns; mail.xyz.com
Diagnostic-Code: smtp; 550 5.1.1 <mike@xyz.com>: Recipient
address rejected: User unknown in virtual alias table
From: Mike <mike@abc.com>
Subject: Test 456
Date: 19 September 2012 22:48:44 BST
To: "mike@xyz.com" <mike@xyz.com>