Many articles on (re)configuring Exchange 2007’s internet-facing Client Access Server contain steps to (re)configure all external URLs. Most of the times this is a list of one or more of the following cmdlets to execute:

• Set-OWAVirtualDirectory –Identity <CASSERVER>\OWA (default web site) -ExternalURL https://someURL/OWA
• Set-OABVirtualDirectory –Identity <CASSERVER>\OAB (default web site) -ExternalURL https://someURL/OAB
• Set-WebServicesVirtualDirectory –Identity <CASSERVER>\EWS (default web site) -ExternalURL https://someURL/ews/exchange.asmx
• Set-ActiveSyncVirtualDirectory –Identity <CASSERVER>\Microsoft-Server-ActiveSync (default web site) -ExternalURL https://someURL

In Exchange 2010 this process has been made easier because Exchange 2010 setup will ask you if it’s an “external facing” Client Access Server, after which it will configure externalURLs for you. But what if you want to reconfigure the setting afterwards? Exchange 2010’s Configure External Client Acess Domain to the rescue! To access it, start Exchange Management Console, expand Server Configuration and select Client Access node. Now either click Configure External Client Access Domain in the right pane or select it after right-clicking.

After entering the new external domain and adding the Client Access Server(s) to which to apply the setting, click Configure.

As you can see from the progress windows, the new URL will be set as ExternalURL for the virtual directories. Note that you can ignore the warning on setting the ExternalURL identical for ‘owa’ and ‘ecp’ to the same value using Set-ECPVirtualDirectory, because the wizard will do that for us.