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Force Outlook 2003 to use RPC over HTTP

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  • Force Outlook 2003 to use RPC over HTTP


    We have the following setup:

    ISA 2006 (Reverse Proxy)
    Exchange 2003 (SP2) Front End on Windows 2003 SP1
    Exchange 2003 (SP2) Back End on Windows 2003 SP1

    We have some roaming users. When they are at work they connect to Exchange via Outlook 2003 using the normal MAPI. When they go home they connect to Exchange via another Outlook Profile (on the same laptop) configured to use RPC over HTTP. At home these users have a connection (adsl or cable) with work but with limited ports open.

    Users complain that when connecting from home it is initially very slow to connect to the exchange server.

    After some testing we have noted that when at home the outlook client first tries to connect using normal mapi and then falls back to rpc over http.

    This behavior seems to occur because the outlook client can resolve the name of the backend server.

    When we configured the laptop to use a bogus dns and then entered the url for the rpc over http proxy in the hosts file it worked fine.

    My question is, is there a way to force outlook to use rpc over http?


  • #2
    Re: Force Outlook 2003 to use RPC over HTTP

    I believe if you go into the exchange proxy settings and check the last two boxes this should accomplish what you are after. Don't hold me to this as i've never tried it.
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    • #3
      Re: Force Outlook 2003 to use RPC over HTTP

      Thanks for you reply. I believed that those settings used to do the trick. It doesn't seem to always be case though.

      Seems that as long as Outlook can resolve the names of the Exchange backend server where the mailboxes are, Outlook will try to connect through normal mapi and then after failing will try RPC over HTTP....


      • #4
        Re: Force Outlook 2003 to use RPC over HTTP

        I don't think you can. It is highly unusual for the backend server to have a name that can be resolved. I don't think I have ever built a site where that occurs unless the user is connecting on a VPN. Saying that - I have deployed RPC over HTTPS in the past with the speed options enabled and Outlook has connected on HTTPS whether inside or outside of the network.

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        • #5
          Re: Force Outlook 2003 to use RPC over HTTP

          The following registry key did the trick. When you apply the registry key below Outlook will only try to connect using RPC over HTTP even though it can resolve the Exchange Back End Servers.

          For Outlook 2003 on Windows Vista and Windows XP:
          DWORD = DisableRpcTcpFallback
          Value = 1

          For Outlook 2007 on Windows Vista and Windows XP:
          DWORD = DisableRpcTcpFallback
          Value = 1

          Note: The RPC Key is not present by default on the clients. So you will have to create it first and then create the DWORD under it.


          • #6
            Re: Force Outlook 2003 to use RPC over HTTP

            Can you post where you found them please.
            If there is an MS KB then that would be handy.

            Please read this before you post:

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