Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Thu, 21 Aug 2008 21:56:27 +0200 (MEST)

The original message was received at Thu, 21 Aug 2008 21:56:24 +0200 (MEST)
from orange-sk-239-226.orange.sk [213.151.239.226] (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 [10.99.150.64]:
>>> DATA
<<< 550 5.1.1 User unknown
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need Rcpt command.