OK. We have a single Exchange 2003 server behind an ISA 2006 server. We publish OWA via ISA Forms Based Authentication. I just recently completed the installation of our new Exchange 2007 server. Exchange 2007 is now parallel to our 2003 box, the routing connectors are in place and I've tested message flow inbound/outbound and between 2003/2007, this all works fine.
Here's the question: Can I, without an incredible amount of work and effort, continue to allow access to 2003 mailboxes via OWA while also allowing access to 2007 mailboxes via OWA? If so, how? There are alot of articles available online, but most of them are very complex. Would it be easier to just move all of the mailboxes to 2007 then reconfigure the OWA publishing to 2007? I assume this would require changing the rules on ISA, assigning a new cert to ISA and to Ex 2007, but I'm not sure what needs to happen with internal DNS or if I need to change the public name that users will enter into their browser to access OWA when outside of the network.