Information
This policy setting controls whether Outlook uses remote procedure call (RPC) encryption to communicate with Microsoft Exchange servers.
If this policy setting is enabled, Outlook 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.
The recommended state for this setting is: Enabled.
Rationale:
By default, the remote procedure call (RPC) communication channel between an Outlook client computer and an Exchange server is encrypted. If this policy is disabled, an end user may modify this setting creating an opportunity for malicious eavesdropping of network traffic between Outlook client and the Exchange server.
Impact:
This is the default behavior and would only impact unsupported versions of Outlook.
Solution
To establish the recommended configuration via GP, set the following UI path to Enabled:
User Configuration\Administrative Templates\Microsoft Outlook 2016\Account Settings\Exchange\Enable RPC encryption
Default Value:
RPC Encryption is used by default but can be overridden by per-profile settings.