Hello,We have a Windows 2003 domain with Exchange 2003 Frontend Backend topology implemented. Recently we installed a Windows 2008 additonal domain controller to the forest. I am in the process of implementing Exchange 2007. We will only use MBX, HT and CAS roles. MBX role will run on a seperate hardware and HT/CAS will run on another hardware. I am have some questions regarding the implementation and I hope you guys could answer my concerns. Please find below my questions:1. As I have a Exchange 2003 frontend server installed, should I start by installing Exchange 2007 CAS Server? 2. Is there anything to be concerned of with OWAoperation on Exchange 2003 while doing this exercise?3. I am planning to have HT and CAS roles run on the same hardware. Should I install HT role along with CAS or should I install MBX role first and then come back to this server and install HT role?4. As I have Exchange 2003 backend server, I believe I need to have HT role installed for routing between exchnage 2003 and exchange 2007. Is this right?TIA

First of all before doing all this in your live enviornment please prepare a test bed so that you can find some answers of your queries .Answer 1 + 2 : http://www.msexchange.org/articles_tutorials/exchange-server-2007/migration-deployment/replacing-exchange-2003-frontend-owa-server-exchange-server-2007-client-access-server.htmlAnswer 3:First of all you have to installed a hub transport server so that your email routing channel has established .yes hub + cas on a single machine works fine and then installed mailbox server .http://www.msexchange.org/tutorials/Transitioning-Exchange-2000-2003-Exchange-Server-2007-Part1.htmlanother imp link for you .http://social.technet.microsoft.com/Forums/en-US/exchangesvrmigration/thread/fe60b040-19d6-40c3-9e1e-fded22e90067.Regards Syed Arsalansyed.arsalan

Added to syed info...My suggestion, firstly install the HUB and CAS roles on one server (Before installing use EXBPA for rediness check), after a successful installation of HUB/CAS server do the necessary changes in IIS (Redirecting OWA page to /OWA directory, were in Exchange 2003 you have to redirect to /Exchange directory), also across check the global settings in Exchange 2007 snapin (Withrespect to send connectors and receive connectors).Any custom disclaimers on front end server, put the same on the new HUB server.Modify the Perimeter devices settings (Spam Filter or Router or Firewalls) pointing to the new HUB/CAS server IP.Modify the receive connectors in Exchange 2007.Cross check the mail flow through the new HUB server and if all goes smooth decommision the Front end server after a period of time.Than go with the Transistion of Exchange 2003 to Exchange 2007Articles and links are suggested by Syed in his reply ......Good Luck....

For question 1 and 3: If you want to deploy the server roles for your organization on more than one computer, and if you are installing Exchange 2007 into an existing Exchange 2003 or Exchange 2000 organization, we recommend that you deploy the server roles in this order: 1. Client Access server role 2. Hub Transport server role 3. Mailbox server role ---------Refer to <Deploying Server Roles> For question 2: Outlook Web Access and Exchange 2007, 2003 and 2000 coexistence For question 4, answer is yes

Thanks much

Thanks all