Email Error

# I've changed the actual domain to website.com for privacy reasons, hope you understand.

This is the mail system at host website.com.

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

<Moz@website.com>: User unknown in virtual alias table

Final-Recipient: rfc822; Moz@website.com
Original-Recipient: rfc822;moz@website.com
Action: failed
Status: 5.0.0
Diagnostic-Code: X-Postfix; User unknown in virtual alias table