Microsoft Exchange Client computers and Microsoft Exchange Server computers communicate using Windows NT Server remote procedure calls (RPCs). To increase the security of data communication between clients and servers, Microsoft Exchange Server enables users to take advantage of the built-in RPC security feature called encrypted RPC. Microsoft Exchange Client can be configured to use encrypted RPCs so communication between clients and servers is secure and messages can't be tampered with during transit.
Encrypted RPC uses a 40-bit RSA algorithm called RC4 to encrypt data while it is on the network. Once the data reaches the destination computer, it is no longer encrypted. Encrypted RPCs provide increased security for messages sent on internal networks, as well as outside organizations, for example, to the Internet.
Encrypting RPCs is different from encrypting a message using advanced security. Encrypted RPC provides protection for data only while it travels on the network from point to point. A message encrypted using advanced security is protected until the recipient decrypts it using Microsoft Exchange Client, regardless of how many hops are used during delivery.
1. From the Tools menu in the Microsoft Exchange Client, choose Services.
2. In the list of information services, select Microsoft Exchange Server, and then choose Properties.
3. Select the Advanced tab.
4. Under Encrypt information, select both options to encrypt all client/server communication.