When Microsoft Exchange Client is installed, it sets the default RPC protocol binding order. This setting determines the protocol sequence that Microsoft Exchange Client uses to communicate with Microsoft Exchange Server. You can change the RPC binding order before or after the client is installed.
Performance can be improved by changing the RPC binding order if the client uses multiple protocols or if the single protocol your client uses is not the first listed in the RPC binding order. If the protocol used is last in the sequence, Microsoft Exchange Client attempts to bind over the protocols listed before it when connecting to the server.
The protocols are represented in the binding order, using the following entries. The string ncacn refers to Network Computing Architecture Connection.
| Protocol name | RPC protocol string |
| Local RPC | ncalrpc |
| Transmission Control Protocol/Internet Protocol (TCP/IP) | ncacn_ip_tcp |
| Sequenced Packet Exchange (SPX) | ncacn_spx |
| Named pipes | ncacn_np |
| NetBIOS | netbios |
| VINES IP | ncacn_vns_spp |
For example, the following entry attempts to establish connections over SPX, TCP/IP, and NetBIOS in that order.
RPC_Binding_Order=ncacn_spx,ncacn_ip_tcp,netbios