Outlook/Exchange Network Traffic

This is an excellent article:
Control Client Network Traffic

It contains an interesting discussion of the Exchange Provider binding order contained in

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ Exchange\Exchange Provider\ Rpc_Binding_Order

The article defines them as follows:

Network Protocols for MAPI Clients
Registry protocol	Meaning
ncalrpc	Local RPC calls (client and server on the same system).
ncacn_ip_tpc	TCP/IP transmitted over Winsock. The client locates the server using DNS, a local hosts files, or a raw IP address, but not NetBIOS.
ncacn_spx	Novell SPX using the NetWare Bindery to locate the server. NetBIOS is not used.
ncacn_sp	Named pipes. The client locates the server using a NetBIOS computer name, WINS, or LMHOSTS.
netbios	The default NetBIOS protocol.
ncacn_vns_spp	Banyan VINES.

And recommends removing the bindings that you do not use. e.g. vines, novell....