So our environment is basically we have an Exchange 2003 server, and we're attempting to move to Exchange 2010 gradually, and move to new hardware while we're at it.
So our first step was obviously to get Exchange 2010 installed on the new box. However, after running the domainprep steps listed in http://technet.microsoft.com/en-us/library/bb125224.aspx (including PrepareLegacyExchangePermissions) our mailbox permissions get messed up.
Normally, we have an AD security group for Exchange Administrators that allows anyone in that group to view all folders inside any user's mailbox. However, now, this functionality is gone and our Exchange Admins can't access anyone's mailboxes. We'd like to get this functionality back if we could.