Having a problem with a transition from exchange 2003 to 2007 at the OWA level. I have an existing Exchange 2003 fe/be scenario. I have installed and introduced an exchange 2007 mailbox/hub server along with a separate cas server. I am able to move mailboxes from exchange 2003 to 2007 and access these mailboxes on exchange 2007 using outlook. I can also access these mailboxes through the cas server using the /owa virtual directory. However I receive an http 503 Service Unavailable error when accessing /exchange. Oviously we want to be able to point users to the /exchange virtual directory to accommodate those still on exchange2003 as we move them to exchange 2007 without having to track and notify each user to use /owa instead of /exchange as their mailboxes move (about 1200) to the new server. This error comes AFTER authenticating. I have seen cases mentioned where this error might appear before even seeing the forms based authentication page. We are able to get to that point. I reviewed the transistion scenarios that talk about the backwards compatibility of using /exchange but I dont see anything mentioned for the issue I am experiencing with the 503 error. Hope to get this resolved asap so we can get this environment into production and transitioed before the end of this month.

Really hoping someone might have some ideas. To summarize. When I hit the CAS server using /exchange it will not load users mailbox that resides on exchange 2007 it just keeps dropping back to the authentication page. It will however redirect to exchange 2003 mailboxes. I must use /owa to load users mailboxes on exchange 2007. This goes against what I understand in that /exchange should redirect accordingly for both exchange 2007 and exchange 2003 users. This is a simple default install with no changes so I dont understand whats going on here.

Hi Scott,Which is the Roll up update installed on the Exchange 2007 CAS and MBX Servers? Is it RU9?Check out this article which talks about OWA co-existence. And yes /exchange would redirect to /owa for a exchange 2007 mailbox.Outlook Web Access and Exchange 2007, Exchange 2003, and Exchange 2000 Coexistencehttp://technet.microsoft.com/en-us/library/bb885041.aspxUpdate the RU if its not the latest?Try to access https://localhost/exchange on CAS and see if its redirected to /owa for a 2007 mailbox and you get the OWA page?If there are any issues in accessing /exchange then recreate the OWA related v-dir as per method 1 of KB 941201Also try to browse https://localhoston the CAS and check if you get the same Service Unavailable errorIf you are getting the same error then check the application logs for event 2274, 2268. You would have to follow the article 894435 and re-register ASP.NETHarpreet Singh Khandiyal (http://support.microsoft.com/kb/555375)

Also this will server more information Outlook Web Access and Exchange 2007, 2003 and 2000 coexistence http://msexchangeteam.com/archive/2007/02/07/434523.aspx Vinod |CCNA|MCSE 2003 +Messaging|MCTS|ITIL V3|

Hi,Before trying to do the check based on the below article, I suggest we first implement the steps according to the Harpreet's suggestions in order to rule out the possible cause of the issue.1, Check the authentication for Exchange-related Virtual Directories in Exchange 2007:http://msexchangeteam.com/search/SearchResults.aspx?q=owa+authentication&PageIndex=22, Troubleshooting Outlook Web Access Logon Failures in Exchange Server 2007 (Pay attention to the point 5)http://msexchangeteam.com/archive/2008/12/31/450340.aspxThanksAllen