I am planning a future upgrade to Exchange 2007 SP1 and want to know if this scenario would work: Current Exchange 2003 SP2 environment: 2 front-end servers load (both virtual) load balanced through ISA 2006 (also virtual) 1 front-end server (older, physical)acting as the bridgehead as well as using OWA through an older ISA 2000 box with a separate cert that will expire this January 4 back-end mailbox servers (physical) What I would like to do: Build 2 Exchange 2k7 client access servers as Server 2K8 VM's (we are a VMWare ESX 3.5 shop, I know VM's are technically not supported by MS) Create a new server farm with the new client access servers and configure ISA 2006 to run OWA/OMA and Outlook Anywhere through it. I would export and install the existing SAN certs to the new servers. I already have the autodiscover.<domain namespace> configured on the cert. Create 2 Hub Transport VM's.Build 3 mailbox servers (physical) and move some mailboxes over to the new server From what I read, there should be no connectivity problems with OWAand Exchange 2K3if the only the CAS role is installed but I would like to decommission the old FE server and re-ip one of the new HT servers with its IP address since some internal apps relay through it via IP address. Does this setup make sense and would there be a problem removing the bridgehead/FE server? Any help/insight would be appreciated.

Dear customer: Because there are multiple servers and virtual directories involved in these coexistence scenarios, it can be difficult to understand which virtual directories users should access. Users should access virtual directories as follows: o Users who have mailboxes on Exchange 2007 computers should access /owa or /exchange on the Client Access server. /owa will take the user directly to Outlook Web Access. /exchange will use DAV to redirect the user to /owa. o Users who have Exchange 2003 or Exchange 2000 mailboxes should access /exchange on the Client Access server. This will return the Exchange 2003 Outlook Web Access experience or the Exchange 2000 Outlook Web Access experience. Davex.dll will redirect the user to the correct server if it is necessary. The simplest strategy in a coexistence scenario is to have all users access the /exchange virtual directory and let the Client Access server redirect users to the correct virtual directory if it is necessary. Additionally, you should confirm you can send and receive e-mail via Exchange Server 2007 before removing legacy Exchange server. For more information about Outlook Web Access and Exchange 2007, Exchange 2003, and Exchange 2000 Coexistence, please refer to the following documents: Outlook Web Access and Exchange 2007, Exchange 2003, and Exchange 2000 Coexistence http://uat.technet.microsoft.com/en-us/library/bb885041(EXCHG.80).aspx Hope it helps. If anything is unclear, please feel free to let me know. Rock Wang - MSFT