I keep getting emails bouncing off our Exchange 5.5 server. The emails show no originator. I have had troubles in the past when there were originators and I was able to block them. Here is an example of an email. This was rejected by another server. How can I setup my server to do the same?

Thanks!

A mail message was not sent due to a protocol error.

501 Anonymous Senders Prohibited
The message that caused this notification was:


To: <[email protected]>
From: <>
Subject: Undeliverable: workcompcentral.com News 4/16/02: Everest; P&C; WI; WCIRB; FL