front-end Exchange 2007 for OWA with a exchange 2003 back-end

We will be looking to migrate to exchange 2007 but the first thing we want to do is install a front-end server. Can we set up a new front-end server with exchange 2007 for OWA, and continue to use our exchange 2003 as a back-end? Thanks.
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BertlingConnect With a Mentor Commented:
hi there once you added the 2007 server to the exchange org then installed a client acces server for owa etc users on both exchange server will be able to access owa through this 1 exchange 2007 front end/client access server.

here i how it work:
uers who have thir mailboxes moved over to the new exchange 2007 can access owa using https://exchange2007casname/owa and they will use the owa 2007 version.

users who still have their mailboxes on the old 2003 erver will have to access owa using this link http://exchange2007casname/exchange.
these users will view owa in the old 2003 style feel.

then aim to move every one over and get rid of the old 2003 server ;)
fina27Author Commented:
Well the plan was to eventually get another server to replace the exchange 2k3 server. We wanted to leave the OWA server as the OWA front-end server once it's in place. I just wanted to know if its possible to have an exchange 2007 as a front-end while having an exchange 2003 as a back-end
atkjediConnect With a Mentor Commented:
You can have exchange 2007 CAS role as "the" front end server but you cannot have 2003 front end and 2007 CAS working together

so in short yes you can but only install the CAS role, in fact CAS should be the first role you install when moving to Exchange 2007

CAS is client access = OWA, Activesync, Etc.

Not trying to take Bertling's point just clarifying
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Q: "just wanted to know if its possible to have an exchange 2007 as a front-end while having an exchange 2003 as a back-end"

A: as i said above the users will have to be advised what backend server they currently are on.
on 2003 they will use https://new2007casserver/exchange
on 2007 they will use https://new2007casserver/owa

users still with their mailbox on the 2003 backend will only be able to use the old 2003 version of owa until there mailbox is moved over.

here is a link to calarify this
fina27Author Commented:
Okay but isnt a front-end exchange 2003 sever designed to be on the DMZ and the CAS on the LAN? There isnt anything wrong with that?
the CAS can still be installed in a DMZ but will relace the 2003 FE owa server.
Sorry to contradict, but.....

CAS should not be installed in a DMZ, especially once you start brining in the E2k7 Mail and Hub roles into your org.

Edge in 2k7 is designed to be in a DMZ and do mail filtering\AV

here is the quote from exchange team
"You should NOT put CAS in the DMZ.  It's not a scenario we test, support, or recommend.  CAS isn't designed to live there.  ISA is designed to work in the DMZ.  You can put ISA there, and have it connect to the CAS in your internal network."

and here

did say to do it, i said it CAN be done if you want to replace the 2003 FE in the DMZ
Well OK, if you put it that way :-)

I personally would not recommend it but rather put it inside and use a reverse proxy (like ISA publishing) in the DMZ to protect it.
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