Exchange 2000 and Outlook/98/2000

I wish to block certain junk mail I and my users receive. I have Exchange 2000 server and users with outlook 98/2000 on a Microsoft 2000 and 98 network. I would like to be able to block messages from certain senders like joe@spam.com or anything @spam.com etc….. It would be easier to do domain wide from the exchange server but outlook blocks at the workstation can work if need be.