Details
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 ConfigurationAdministrative TemplatesMicrosoft Outlook 2013SecurityCryptographySend 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.
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: System and Communications Protection.This control applies to the following type of system Windows.