Hi Running Exchange 2007 SP2 with three main AD sites. Each AD site has a seperate DC/GC, Mailbox cluster, CAS and Hub servers. Sites are London, LA, NY. For CAS servers, we have Cisco load balancers in place at each site, all users use https://webmail.domain.com to access their OWA. Also, our networking guys have implented a function whereby users are routed to their closest load balancer when accessing webmail. So a user from London (whose mailbox is on Lond-MBX1 server) travels to NY. When in NY, they type in https://webmail.domain.com to access their email. This should route them to the NY load balancers which then send him to a NY CAS, e.g. NY-CAS1. What happens here? Does Exchange proxy the connection to a CAS in London, since that's where his mailbox is? So, really when he's accessing OWA, he's accessing Lond-CAS1 or Lond-CAS2? Or is he accessing NY-CAS1, which has a connection directly to Lond-MBX1 to grab the data?

Hi, Normally the user would be redirected to the internal url of a CAS server in London, but it is not possible to tell what happens here because you might have some configuration in place here that operates in a different way. Leif

Hello, Are all the CAS servers are internet facing? We can use CAS proxy when one Client Access Server can act as a proxy for other Client Access Servers within the organization, when multiple Client Access Servers are present in different Active Directory sites in an organization and only one is exposed to the Internet. For more reference, please see the following article: Understanding Proxying and Redirection http://technet.microsoft.com/en-us/library/bb310763.aspx Thanks, Simon

Thanks both. To confirm, we don't have internet facing CAS servers, i.e there is no ExternalURL value set, this is all Internal. Based on that info, could someone confirm what is happening? i. The user's browser is accessing NY CAS, but the actual NY CAS 'fetches' all the data from the London CAS, which in turn gets the data from the Lond-MBX1 server? ii. The user's browser initially accesssed NY CAS, but then is directed to London CAS? Thanks guys.

Hello, If the user's mailbox is on an Exchange 2010 Mailbox server in a different Active Directory site, the proxy CAS (Let’s call it CAS-01) server locates a CAS (Let’s call it CAS-02) server in the same Active Directory site as the user's Mailbox server. When one is found, Exchange 2010 determines whether the CAS server has the ExternalURL property set in that Active Directory site. If so, the user is provided with a clickable link that redirects them to the specified URL. If the ExternalURL isn't set and the authentication method on the virtual directory is set to Integrated Windows authentication, CAS-01 will proxy the user's request to the CAS-02 that's specified by the InternalURL property. Thanks, Simon

Ok, this is for Exchange 2007 by the way, not 2010, but I assume it's the same?. So, if I went to user's browser > OWA > About What value should I see for: Client Access Server: Proxy Server:

Yes, this machanism applies for both Exchange 2007 and Exchange 2010. Client Access Server: This should be the CAS serer which is in the same site of the mailbox. Proxy Server: The CAS server you origianlly access in IE. Thanks, Simon