Subject: Warning: could not send message for past 4 hours

From: Mail Delivery Subsystem <[email-masked]>
Date: Wed, 27 Aug 2008 14:50:15 +0800

**********************************************
    **      THIS IS A WARNING MESSAGE ONLY      **
    **  YOU DO NOT NEED TO RESEND YOUR MESSAGE  **
    **********************************************

The original message was received at Wed, 27 Aug 2008 06:09:52 +0800
from [210.210.251.221]

   ----- Transcript of session follows -----
... while talking to [89.105.145.163]:
>>> DATA
<<< 450 <[email-masked]>: User unknown in local recipient table
<[email-masked]>... Deferred: 450 <[email-masked]>: User unknown in local recipient table
<<< 554 Error: no valid recipients
Warning: message still undelivered after 4 hours
Will keep trying until message is 5 days old