Email - hotmail "Undelivered Mail Returned to Sender"

Hvorfor får jeg pludselig 20 mail af nedenstående slags, og hvad gør jeg for at undgå det?

Jeg benytter mig af Hotmail.


En mail kunne fx. se sådan ud:

"This is the Postfix program at host cicero1.cybercity.dk.

I'm sorry to have to inform you that the message returned
below could not be delivered to one or more destinations.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the message returned below.

            The Postfix program

<dsl58495@vip.cybercity.dk>: host vip.cybercity.dk[212.242.41.36] said: 552
    Error: W32/Sobig.f (in reply to end of DATA command)


Reporting-MTA: dns; cicero1.cybercity.dk
Arrival-Date: Tue, 26 Aug 2003 13:07:48 +0200 (CEST)

Final-Recipient: rfc822; dsl58495@vip.cybercity.dk
Action: failed
Status: 5.0.0
Diagnostic-Code: X-Postfix; host vip.cybercity.dk[212.242.41.36] said: 552
    Error: W32/Sobig.f (in reply to end of DATA command)


From :   
<sidal25@hotmail.com> 
   
To :   
<dsl58495@vip.cybercity.dk> 
 
Subject :   
Thank you! 
 
Date :   
Mon, 25 Aug 2003 13:03:29 +0200 
 
Attachment :  your_document.pif (48k)   
See the attached file for details"