Problem:

How do I setup Microsoft Exchange 2003 to only accept email from the proFilter clusters?
How do I setup Microsoft Exchange 2007 to only accept email from the proFilter clusters?

Solution:

1. Run Microsoft Exchange System Administrator:-

   Go to Start->Programs->Microsoft Exchange->System Manager

2. Expand the following trees:-

   Servers -> (Your Server) -> Protocols -> SMTP

3. Right-click on Default Virtual SMTP Server

4. Click on Properties

5. Click on the Access tab

6. Click on the Connections button

7. Ensure that the Only the list below radio-button is selected

8. Use the Add button repeatedly to add all IP addresses from the list below

9. Click OK on all dialog boxes.

10. Right-click on Default Virtual SMTP Server

11. Click on Stop

12. Wait for the service to stop

13. Right-click on Default Virtual SMTP Server

14. Click on Start

15. Wait for the service to restart.
    

The IP addresses of the proFilter clusters can be found in the article: Profilter IP Addresses