Issue 1 – You are ready to de-install Exchange 2003
You may receive the error-message: “One or more users currently use a mailbox store on this server. These users must be moved to a mailbox store on a different server or be mail disabled before uninstalling this server.”
Solution: Use NOT your Windows Server 2003 Active Directory Users and Computer.
Use a newer Server 2008 Domain Controller “Active Directoy Users and Computers” (or 2008 R2 / 2012 / 2012 R2) and perform a “Find” for all of your users inside your Domain(s). Extend the search result pane with the column “Exchange Home Server” and you may see (only here!) some users pointing to your legacy Exchange 2003 server.
And now? Go to them with your AD Attribute Editor and clear the Attribute: mxExchHomeServer
Voila, you are ready for the last last call –> de-installation – bye bye Exchange 2003 :-)