I recently setup a BES 5.0 server and everything is working great with the Exchange 2007 server in our primary domain. Unfortunately, I'm unable to activate a user in our child domain. The mail server in the child domain is running Exchange 2003. I've double checked the service accounts' permissions and have narrowed it down to an Exchange not an AD problem.

When I first setup BES I installed the ExchangeMapiCdo.EXE only. I did not install the Exchange System Manager. I believe ESM is needed on the BES to connect to Exchange 2003. Can I install the Exchange tools without affecting the working connection I have with our Exchange 2007 server?

Thanks!

The ExchangeMapiCdo.exe is all you need.

does mail flow from those servers?

Does BESAdmin have permissions on the 2003 server?

Yes, mail flows from each server. I've triple-checked the permissions for the BESADMIN account on each server. Everything appears to be correct. I've been doing some testing using the IEMSTEST.exe. All users hosted on the Exchange 2003 server fail. The one user located in the child domain but hosted on the Exchange 2007 server passes the test. I believe that rules out the AD permissions.

Another post mentioned checking the MAPI32.DLL versions among the servers. Not sure how it works but here they are...
BES = 1.0.2536.0
Ex2007 (working) = 1.0.2536.0
Ex2003 (not working) = 6.5.7654.12

Thanks again for the help!

Your MAPI is fine.

Your symptoms point to a BESAdmin permission issue on the E2K3 server.