I am currently using Exchange 2003 and Postini. I finally got my invitation to transition to Google Apps but the invitation includes says "Your mail server is not yet configured correctly". The link takes me to a page with instructions for configuring your firewall and mail server to allow email from Google IP's. The problem is that I added the IP's to the Exchange server months ago. My firewall forwards port 25 using NAT to the Exchange server.
How can I test to find out if my configuration is correct?