Exchange 2010 Server Hosting OWA for Exchange 2007 Clients?

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Willard Martin


Going through the Exchange team blog site (specifically,, I found information about configuring an Exchange 2010 CAS for coexisting with Exchange 2007 and Exchange 2003 mailbox servers. in the information, it said to give OWA 2003 a legacy URL, but it gave these steps for configuring support for Exchange 2007 OWA:

If you have Exchange 2007 deployed in "Non-Internet Facing AD Sites" then you must copy the Exchange 2007 OWA binaries to CAS2010:
On the CAS2010 server(s), establish a connection to the CAS2007 server's drive that contains the Exchange binaries and navigate to the \Client Access\OWA directory (e.g. \\cas2007\c$\Program Files\Microsoft\Exchange Server\Client Access\Owa). Copy the highest version folder (e.g. from the CAS2007 to CAS2010 Exchange binaries \Client Access\OWA directory (e.g. C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\Owa). Execute IISReset on all the CAS2010 machines.

I had heard that the Exchange 2010 CAS wasn't able to support Exchange 2007 OWA connections, but this belies that notion. Since this came from the Exchange team's blog, I have to assume this changed, but I'm looking for confirmation. If this is the case, do I need to keep the Exchange 2007 CAS servers if I have no Exchange 2003 mailboxes in my environment? Thanks.

Brian Desmond -MVP-

So the bit you pasted is about proxying. The Exchange 2010 CAS server will render OWA for Exchange 2007 mailboxes, but, it will proxy the connections behind the scenes to an Exchange 2007 CAS server in the user's home site.

Active Directory, 4th Edition -

Steve Goodman

Just to add to what Brian said - the reason you copy those files across is although Exchange 2010 can proxy to the 2007 server, it needs the resource files (like .css, images) copied across from the 2007 CA to render to the client. That's why you copy that folder across.


Steve Goodman
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AndyD_ [MVP]

and the key point is that the proxying is to non-internet facing 2007 OWA servers, not internet-facing 2007 CAS.

If the 2007 CAS is internet-facing ( i.e. the externalURL is populated), then the user is redirected, not proxied and the session then continues directly with the 2007 CAS, not through the 2010 CAS.

And yes, keep the 2007 CAS around until all the 2007 mailboxes are moved.
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