Delivery Status Notification (Failure)

The following message to <meis01100p@istruzione.it> was undeliverable.
The reason for the problem:
5.x.0 - Message bounced by administrator
The original message was received at Wed, 13 Jul 2005 08:57:49 +0200
from [127.20.200.33]

----- The following addresses had permanent fatal errors -----
<meis01100p@istruzione.it>

----- Transcript of the session follows -----
... while talking to 217.127.242.223:
>>> MAIL From:lurker@lists.plug.phoenix.az.us
<<< 506 User unknown