When all mailboxes, public folders, and other services have been migrated to Exchange Server 2007 it is time to remove the Routing Group Connectors between the Exchange 2003 routing group and the Exchange 2007 routing group.

If you have Routing Group Connectors that you want to still keep then use Get-RoutingGroupConnector to show all of the RGCs, and then use Remove-RoutingGroupConnector to remove the specific ones you no longer need.

If you simply want to remove all RGCs between Exchange 2003 and Exchange 2007 (which is common for simple Exchange organizations) you can use this simple Exchange Management Shell command.

[PS] C:\>Get-RoutingGroupConnector | Remove-RoutingGroupConnector -confirm:$false