Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Tue, 12 Aug 2008 10:09:57 -0400

The original message was received at Tue, 12 Aug 2008 10:09:53 -0400
from 200-233-185-156.xf-static.ctbcnetsuper.com.br [200.233.185.156]

   ----- The following addresses had permanent fatal errors -----
<[email-masked]>
    (reason: 550 5.1.1 <[email-masked]>... User unknown)

   ----- Transcript of session follows -----
... while talking to mx.citynet.net.:
>>> DATA
<<< 550 5.1.1 <[email-masked]>... User unknown
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.0.0 Need RCPT (recipient)