??? !!! ???If one or more of the RPC registry entries are missing, Outlook may not connect to Exchange Server. If the ClientProtocols subkey or data values are missing, the Outlook client may not be able to use the expected protocol to connect. For Outlook to use the appropriate RPC protocol, the ClientProtocols subkey and data values must be present and accurate.
For example, on the computer that is running Outlook, if the only RPC ClientProtocols registry entry that is present is ncacn_np (with a value of rpcrt4.dll), Outlook tries to connect to the computer that is running Exchange Server by using named pipes over TCP/IP on the default port of 139. If the connection must traverse a firewall, port 139 must be open. The missing registry entry ncacn_ip_tcp (with a value of rpcrt4.dll) must be restored to support a TCP/IP connection that uses port 135 or port 445 to the Exchange Server.