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How to Verify That RPC Proxy Server Extension Is Loading Properly


This topic is among a series of steps to help you troubleshoot an unsuccessful RPC over HTTP connection. This article explains how to verify that the RPC Proxy Server Extension is loading properly.

If Outlook clients experience connection problems after you configure all the required settings for RPC over HTTP on the server side, it may be because the RPC Proxy Server Extension is not loading correctly. When clients experience this kind of connection problem in Outlook, they receive an error message that is similar to the following:

Exchange server is unavailable.

To verify that the RPC Proxy Server Extension is loading correctly, follow the steps below.


To verify that the RPC Proxy Server Extension is Loading Properly

  1. On the Exchange Server, click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager on your RPC proxy server.

  2. Under the icon for your RPC proxy server, click Web Service Extensions.

  3. In the right pane, click RPC Proxy Server Extension, and then click Properties.

  4. Confirm that the path of the Rpcproxy.dll file is correct. The correct location is the following:


    For example, the correct location could be the following:


    Examine the path entry carefully because it could be incorrectly set to the following:


    For example, the current location could be set to the following:


    This incorrect path can appear to be correct at a quick glance.


    The Rpcproxy.dll file could be present in both locations; you do not have to delete or modify that file in either of those locations. If you find that this path entry is correctly set, then the Rpcproxy.dll file may be missing or corrupted. If this is the case, the Rpcproxy.dll file may have to be replaced or re-registered.

    Additionally, if you experience this issue, the following 404 error is logged in the IIS log on your RPC proxy server:

    2004-01-01 13:13:31 RPC_IN_DATA /rpc/rpcproxy.dll 443 domain\username MSRPC 404 2 1260

    This 404 error may be caused by a disabled or non-functioning Web service extension. For more information, see the following article in the Microsoft Knowledge Base, 248033: Common reasons IIS Server returns "HTTP 404 - File not found" error.

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