We had BES express 5.0, Server 2003 64 bit and Exchange 2007 on a single box and everything worked for one year.
Uninstalled BES and SLQ from exchange server
Added a new domain controller (Server 2003 32-bit)
Installed BES Express 5.0.2.
The MX Records and the exchange server is on external ip of x.x.x.138
BES is on external ip of x.x.x.137
There is no firewall other then allowing incoming ports.
I have allowed incoming 3101 traffic to x.x.x.137
Followed all the proper steps in the installation guides.
When trying to do an enterprise activation the blackberries time out.

How can I test to see if the BES is communicating properly with RIM
What else am I missing?
This is my 3rd BES installation so I have done it correct twice now.

Hey PCSDave, I'd run IEMSTEST.exe and select one user and ensure there are no errors (typically it will indicate there are permissions or connection issues to exchange if it fails). If this passes, ensure when you are activating to a user, that you are seeing the ETP message get to the inbox and the user isn't deleting it / it's not being filtered. If those ETP messages are NOT getting to the inbox, then you need to ensure you whitelist blackberry.net on any spam filters etc etc

You can do a quick test to ensure things are working properly through your firewall by running telnet srp.us.blackberry.net 3101 and if it doesn't timeout your in the clear. You can also use the SRP test from blackberry config to ensure it's working as well.