Since CAS servers are now the MAPI endpoint for Outlook clients accessing Exchange 2010 mailboxes, it is recommended as a best practice that you create arrays of load-balanced CAS servers in order to provide high availability for the CAS server role. In this recipe, you'll learn how to create a CAS array using the Exchange Management Shell.
In order to create a CAS array, you must use the shell since there is no interface within the Exchange Management Console that allows you to perform this task. The following command creates a CAS array for the CorporateHQ site in Active Directory:
New-ClientAccessArray -Name CASArray01 ` -Fqdn outlook.contoso.com ` -Site CorporateHQ