1.13.2.8 Ensure 'Send all signed messages as clear signed messages' is set to Enabled

Information

This policy setting controls whether Outlook sends signed messages as clear text signed messages.
If you enable this policy setting, the 'Send clear text signed message when sending signed messages' option is selected in the E-mail Security section of the Trust Center.
If you disable or do not configure this policy setting, when users sign e-mail messages with their digital signature and send them, Outlook uses the signature's private key to encrypt the digital signature but sends the messages as clear text, unless they are encrypted separately. The recommended state for this setting is: Enabled.

Rationale:

By default, when users sign e-mail messages with their digital signature and send them, Outlook uses the signature's private key to encrypt the digital signature but sends the messages as clear text, unless they are encrypted separately. If users change this functionality by clearing the Send clear text signed message when sending signed messages option in the E-mail Security section of the Trust Center, any recipients who are unable to access or use the sender's digital certificate will not be able to read the e-mail messages.

Solution

To implement the recommended configuration state, set the following Group Policy setting to Enabled.

User Configuration\Administrative Templates\Microsoft Outlook 2016\Security\Cryptography\Send all signed messages as clear signed messages

Impact:

Enabling this setting enforces the default configuration in Outlook, and is therefore unlikely to cause usability issues for most users.

See Also

https://workbench.cisecurity.org/files/553

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-8(1)

Plugin: Windows

Control ID: eb9f75c5041b166a570e05a3811f4710da61e6594ddab8d8ba0d0ce759241c4f