Under Control Panel choose Parameters for the Email server.Add the spam domain or specific email address to the Reject the following Users/Hosts/Domains area and save.You didn't say which server you have, these instructions are for a Raq4, but they are similar on the other Raqs.
Yes, I realized I had forgotten to say that I am on a RAQ3 - I am checking to see if I have this option.
Thanks for all the responses. JALE