Unable to send Email Notifications

[Charles]

I can't make the Project Server send the email
notifications. I already checked the email notifications
and reminders in Web Access and everything is OK.
I checked the Appilcation Log in the Server (Windows 2000
Server) and i found the following error:

"The server rejected one or more recipient addresses. The
server response was: 550 RCPT
TO:<[email protected]>
Relaying not allowed"

Any one can help me to solve this?
Thanks in advance