Changing Exhange Default Message

[etuero]

How can I alter the default Exchange message when an email address does not exist on the postoffice ?
for example:

Your message did not reach some or all of the intended recipients.

Subject: FW: Domain Names
Sent: 10/8/2001 6:45 AM

The following recipient(s) could not be reached:

Ed Tykwinski (E-mail) on 10/8/2001 6:45 AM
The recipient name is not recognized

I want to put a URL in the default message any ideas how to put a url in the above default message ??

thanks !