This seems to be a long drawn out process. I am upgrading to Exchange 2010 from Exchange 2003. I have 2 MBX servers in a DAG, I have 2 CAS servers in a CAS array. All 4 servers a HT servers. I have moved a test user to the Exchange 2010 environment and that user can't send email to the outside. I can receive from the outside, just can't send.