I'm ready to to uninstall Exchange 2003 after upgrading to 2007. Routing Group Connectors are gone, Public Folders are moved and deleted, Mailbox Storage group is deleted, RUS is deleted. get-mailbox -servername comes back with no entries. But Exchange 2003 Setup won't uninstall saying that there are still mailboxes on the server. Everything looks good but I can't uninstall. [14:46:23] - 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. -- ID:64292 -- [14:46:23] Prerequisites for Microsoft Exchange Connector for Lotus Notes failed: The component "Microsoft Exchange Messaging and Collaboration Services" cannot be assigned the action "Remove" because: - 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.

Got it http://support.microsoft.com/kb/279202