Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Tue, 23 Sep 2008 22:44:34 +0400 (MSD)

The original message was received at Tue, 23 Sep 2008 22:44:31 +0400 (MSD)
from p578b44b5.dip0.t-ipconnect.de [87.139.68.181]

   ----- 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 flux.ptc.spbu.ru.:
>>> DATA
<<< 550 5.1.1 <[email-masked]>... User unknown
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.0.0 Need RCPT (recipient)