Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Wed, 15 Oct 2008 06:08:44 +0200 (CEST)

The original message was received at Wed, 15 Oct 2008 06:07:57 +0200 (CEST)
from localhost [127.0.0.1]

   ----- The following addresses had permanent fatal errors -----
<[email-masked]>
    (reason: 550 5.1.1 <[email-masked]>: Recipient address rejected: undeliverable address: host mailgw-as...[153.96.1.238] said: 550 5.0.0 <[email-masked]>... User unknown (in reply to RCPT TO command))

   ----- Transcript of session follows -----
... while talking to mx09a.antispameurope.de.:
>>> DATA
<<< 550 5.1.1 <[email-masked]>: Recipient address rejected: undeliverable address: host mailgw-ase1.fraunhofer.de[153.96.1.238] said: 550 5.0.0 <[email-masked]>... User unknown (in reply to RCPT TO command)
550 5.1.1 <[email-masked]>... User unknown
<<< 554 5.5.1 Error: no valid recipients