Remote Procedure Call Over HTTP Is Not Successful or Reverts to TCP

When you try to connect to Microsoft Exchange Server 2003 by using a remote procedure call (RPC) over HTTP connection, the connection may not succeed, or the connection may revert to a TCP (Transmission Control Protocol) connection.

This issue may occur if you try to connect to the Exchange server by using Microsoft Outlook with Secure Sockets Layer (SSL) enabled. This issue occurs if the server-based certificate is issued to a different server than the one that you are trying to connect to.

For example, if you have configured Outlook to use https://mail.example.com as the default RPC over HTTP proxy server, but the certificate is issued to a front-end server such as frontend.example.com, the connection is not successful because the client does not recognize the front-end server as a valid server to authenticate with.

To resolve this problem, follow these steps:

1. On the RPC Proxy server computer, click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
2. Expand your domain, double-click Default Web Site, right-click RPC, and then click Properties.
3. Click the Directory Security tab, and then click View Certificate.
4. Make sure that the certificate is issued to the same server that is used by the client.
   
   If you have to, modify the RPC Proxy setting on the Outlook client, or obtain a new certificate for the RPC Proxy server computer.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

To troubleshoot this problem, use one of the following methods.

Method 1: Use RPCPing.exe

Note RPCPing.exe is included with the Windows Server 2003 Resource Kit Tools. To download the resource kit tools, visit the following Microsoft Web site: To use RPCPing.exe to identify this problem, follow these steps:

1. On the client computer, click Start, click Run, type cmd.exe in the Open box, and then click OK.
2. Type the following command, where user and domain are the user name and domain that you use to log on to Outlook :
   rpcping.exe -t ncacn_http -s ExchangeServerName -o RpcProxy=ProxyServerName -P "user,domain,*" -H 1 -u 10 -a connect -F 3 -E -R none
   The other parameters must be defined to connect to your Exchange server in the same way that Outlook does.
3. When you are prompted to do so, type your password.
4. Notice that RPCPing.exe generates the following output:
   RPCPinging proxy server ServerName with Echo Request Packet
   Send ping to server
   Error 12175 returned in the WinHttpSedRequest
   Ping Failed

Method 2: Verify the Certificate

If the RPC Proxy computer is also configured to be a Microsoft Outlook Web Access (OWA) server, start Microsoft Internet Explorer and log on to your OWA mailbox. When you log on, use the same server name that you used for your Outlook RPC Proxy. If you receive a message that you do not have access to the RPC Proxy computer, click View Certificate, and then verify that the certificate was issued to the server that you are trying to log on to.