Going through the Exchange team blog site (specifically, http://msexchangeteam.com/archive/2009/11/20/453272.aspx), 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. 220.127.116.11) 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.