Error message when you try to remove Exchange Server from a mailbox server that no longer hosts mailboxes: "One or more users currently use a mailbox store on this server"
When you try to decommission Exchange 2000 or a 2003 Server from your exchange environment you will get the above error even after moving al mailboxes and services to another Exchange server in the same Org.
This happens because of you are having a user with his Exchange home server set as the server name you are trying to uninstall. Home server is defined in Active Directory with msExchHomeServer attribute
To find and move the affected mailbox to a running exchange server in your organization and perform your uninstall process without troubles, follow the steps below.
Go to Administrative Tools –> Active Directory Users and Computers
Right click on the Domain container and select Find.
In the Find Users, Contacts, and Groups dialog box, click the Exchange tab, click to select the Show only Exchange recipient’s check box, and Users with Exchange mailbox and then click Find Now.
Now to get msExchHomeServer attribute you need to change the view columns.
Go to the View menu, click Choose Columns.
In the Choose Columns dialog box, click Exchange Home Server in the Columns available list, click Add, and then click OK.
Click the Exchange Home Server column to sort the results in the Exchange Home Server column.
Now you can determined is there any user with Home Server attribute set to the affected server, so that you can either move that mailbox to any other available Server or remove the mailbox if its not required.
