What is the role of the Exchange service account in Exchange 2000? Is it needed only for compatibility with Exchange 5.5 or does it play a role with 2000?
We have created a new Active Directory domain and would like to collapse the old NT 4.0 domain. But our Exchange Server 5.5 is the hub in a hub-and-spoke configuration with multiple sites. It was installed with a service account that is the domain administrator account for our old NT 4.0 domain.
I was told that we cannot change the service account without reinstalling Exchange (and without a multiple site configuration). If we install the new Exchange 2000 server in the same site and move mailboxes, we will have to use the same service account that ties to the old domain. Now, if it is only for compatibility, then we could live with that till we would be able to switch our organization to native mode, but if it is here to stay, then we have to look into a different solution.
The Exchange Server service account is granted special permissions in Windows and Exchange, making changing it a very gory procedure. However, Microsoft just so happens to have a whole white paper devoted to the subject entitled How to change the Microsoft Exchange server 5.5 service account. I would read this white paper a couple times before implementing the procedure. You may even wish to have someone from Microsoft PSS on the phone with you while you perform the procedure.
There's also some additional information that might interest you, as well.