our exchange 2007 server has had errors with event 9385 since we dcpromo'ed an old 2003 DC out of our domain. Mail seems to work correctly and the exchange server is in the group "Exchange servers security group" I was thinking i would either restart the SA service or reboot the machine. Will restaring the SA services effect users? The IS and MTA at least will also be affected if i restart the SA correct? Microsoft Exchange System Attendant failed to read the membership of the universal security group '/dc=<domain>/dc=<domain>/ou=Microsoft Exchange Security Groups/cn=Exchange Servers'; the error code was '8007203a'. The problem might be that the Microsoft Exchange System Attendant does not have permission to read the membership of the group. If this computer is not a member of the group '/dc=<domain>/dc=<domain>/ou=Microsoft Exchange Security Groups/cn=Exchange Servers', you should manually stop all Microsoft Exchange services, run the task 'add-ExchangeServerGroupMember,' and then restart all Microsoft Exchange services.

Restating System Attendant will usually bring the other services down as well. Therefore if you have users connected they will be kicked out. As a good rule, if I ever remove a DC in the same site as Exchange, after doing so I will restart the Exchange services shortly afterwards. That will ensure Exchange knows the DC has gone away. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources

Check the DNS settings on your Exchange server - the primary DNS server is probably set to the old DC (which does not host a copy of your Internal DNS zone any more). Failing that - check the other DC's using dcidag.