Subject: Mail delivery failed: returning message to sender

From: Mail Delivery System <[email-masked]>
Date: Wed, 24 Sep 2008 19:15:59 +0300 (EEST)

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

[email-masked]
   SMTP error: 550 5.1.1 <[email-masked]>: Recipient address rejected: User unknown in local recipient table