OWA for Exchange 2003 mailboxes via Exchange 2007 Client Access Server

by Shijaz Abdulla on 20.11.2007 at 09:48

If you are planning on co-existing Exchange Server 2003 backend servers alongside Exchange Server 2007 mailbox servers, you will have the following question lingering in your mind:

But what about Outlook Web Access?

If some of your users have mailboxes on Exchange Server 2003 while others have mailboxes on Exchange Server 2007, and you publish your OWA URL as http://webmail.mycompany/owa, you will notice that Exchange 2003 users get the following error:

Outlook Web Access could not find a mailbox for DOMAINUSER. If the problem continues, contact technical support for your organization and tell them the following: The mailbox may be stored on a Microsoft Exchange 2000 or Microsoft Exchange 2003 server, or the Active Directory user account was created recently and has not yet replicated to the Active Directory site where this Client Access server is hosted.

The solution is to use the URL http://webmail.mycompany/exchange on the Client Access server. The ‘/exchange’ virtual directory on the Client Access server is able to proxy OWA requests for Exchange 2003 mailboxes to the appropriate Exchange 2003 back end server and the user sees the Exchange 2003 OWA experience. The ‘/exchange’ virtual directory will also automatically redirect OWA requests for Exchange 2007 mailboxes to the ‘/owa’ virtual directory.

For more information, see this post on the Exchange Team blog.

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7 Responses to OWA for Exchange 2003 mailboxes via Exchange 2007 Client Access Server

  1. Anonymous says:

    You might want to add the fact that Exchange 2007 mailboxes can also be accessed via the /EXCHANGE virtual directory.

    This means that if you run 2000/2003 as well as 2007 mailboxes (during co-existance say), and you want to use the Exchange 2007 CAS, you should probably publish your company’s OWA logon page via the /EXCHANGE virtual directory.

    This is referenced here http://technet.microsoft.com/en-us/library/aa998849.aspx

    especially with this text:

    “If your organization includes Exchange 2000 or Exchange 2003 mailboxes in addition to Exchange 2007 mailboxes, all users can access Outlook Web Access through the /Exchange virtual directory. The Client Access server will automatically redirect Exchange 2007 mailbox users to the /owa virtual directory.”


  2. Shijaz Abdulla says:

    Thanks Kevin, for the review.

    This was intended, but not mentioned in my post. I’ve updated the post and just made it clearer. Thanks again!

  3. Anonymous says:

    Dear Colleague,
    could you help me with the following.
    I have 1 CAS, 1 Mailbox 2007 and 1 mailbox 2003.

    going to /Exchange on CAS redirects me perfect to 2003 mailbox, going to /owa log me on my mailbox on 2007.

    BUT (!) /Exchange do not redirect me to /owa in case the mailbox is on 2007.

    Probably you have some advices, where to look? Dealing with this already 3 days with no luck!

  4. Anonymous says:

    I have the same problem with one of my mailbox servers. If I go to /owa it works. If I use /exchange it doesn’t redirect me even though the mailbox is on the 2007 mailbox server.

  5. Anonymous says:


    I had a hard time locating the site to resolved my probem. I found it to this site..


  6. Hello all
    i have the same problem.
    1 CAS server
    1 Exch 2007 mailbox server
    1 Exchange 2003

    Looking for the way to type https:/mycompanyCAS/exchange and automaticaly to be redirected to needed server.

    Thanks a lot !

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