This policy setting controls whether Outlook 2007 uses remote procedure call (RPC) encryption to communicate with Microsoft Exchange servers.
If you enable this policy setting, Outlook 2007 uses RPC encryption when communicating with an Exchange server. Note - RPC encryption only encrypts the data from the Outlook client computer to the Exchange server. It does not encrypt the messages themselves as they traverse the Internet.
If you disable or do not configure this policy setting, RPC encryption is not used. This setting allows you to override the corresponding per-profile setting.