Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Fri, 24 Oct 2008 04:47:11 +0400 (MSD)

The original message was received at Fri, 24 Oct 2008 04:47:09 +0400 (MSD)
from cpe-75-81-57-115.kc.res.rr.com [75.81.57.115] (may be forged)

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

   ----- Transcript of session follows -----
... while talking to mail1lg.gk.biostar.ru.:
>>> DATA
<<< 550 5.1.1 User unknown
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need Rcpt command.