≡ Menu

How to Configure CAS proxying in Exchange 2007

This post is mainly concerned about the steps required for enabling CAS proxying in Exchange 2007. Before explaining the configuration part, I will give you the scenario where I am configuring the CAS proxying.


I have two sites, SiteA and SiteB. Both the sites are having MBX and CAS(2) servers.
CAS1 server(SiteACas1) in SiteA is published to Internet.

If a user whose mailbox in siteB mailbox server tries to open his mailbox through OWA from internet, his request goes to SiteACas1 server and he will be get below error.

Error: Outlook Web Access is not available. If the problem continues, contact technical support for your organization and tell them the following: There is no Microsoft Exchange Client Access server that has the necessary configuration in the Active Directory site where the mailbox is stored.

To resolve these errors, follow the below steps.


  • Enable integrated authentication on Cas1SiteB and Cas2SiteB servers.

Set-OwaVirtualDirectory -Identity “Cas1SiteBowa (Default Web Site)” -WindowsAuthentication $true
Set-OwaVirtualDirectory -Identity “Cas2SiteBowa (Default Web Site)” -WindowsAuthentication $true

  • Set the internal URL on both the CAS servers in siteB

set-OwaVirtualDirectory -Identity “Casd1SiteBOWA (Default web site)” -InternalUrl https://Cas1SiteB.local.com/owa
set-OwaVirtualDirectory -Identity “Casd2SiteBOWA (Default web site)” -InternalUrl https://Cas2SiteB.local.com/owa

You are all set here, try accessing your siteB mailbox from CAS1SiteA OWA URL. It should work now.

What else I need to read to understand Proxying and Redirection better:?

TechNet [http://technet.microsoft.com/en-us/library/bb310763.aspx]
Msexchangeteam posts [One, two, and three]

Post here if you need any clarifications or have any questions.

Happy Learning,
Sitaram Pamarthi