blocking IP address

If I understand you correctly, you want to prevent spam mailed from a particular IP address from reaching your users. If this is so, then you can delete the mail before it reaches the users. Straight from TechRepublic's Exchange Tips download "...open Exchange Administrator and view the Properties dialog box for your Internet Mail Connector. Then, click the Connections tab and click the Mail Filtering button. In the resulting Message Filtering dialog box, you will find an interface that allows you to configure" addresses or domains to block using the following format:

#@xxx.xxx.xxx.xxx (blocks all mail from an IP address)

#@domain.com (all mail from a particular domain)

There are other possibilities as well. If this doesn't answeryour question, let me know and I'll see if I can help.