Mail delivery failure

[mailmaster]

****** Message from InterScan E-Mail VirusWall NT ******

Sent >>> RCPT TO: <address@hidden>
Received <<< 550 <address@hidden>... User unknown

Could not deliver mail to this user.
address@hidden
*****************     End of message     ***************
> --- Begin Message ---
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> Subject: 
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> Protected Mail System
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> Date: 
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> Sat, 15 May 2004 14:14:22 +0200
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> Encrypted message is available.
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>
> --- End Message ---