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.

Solution

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography ‘Send all signed messages as clear signed messages’ to ‘Enabled’.

Supportive Information

The following resource is also helpful.

• https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_MS_Outlook_2016_V2R1_STIG.zip

This security hardening control applies to the following category of controls within NIST 800-53: Configuration Management.This control applies to the following type of system Windows.

References

• 800-53|CM-6b.
• CAT|II
• CCI|CCI-000366
• Rule-ID|SV-228455r508021_rule
• STIG-ID|DTOO264
• STIG-Legacy|SV-85855
• STIG-Legacy|V-71231
• Vuln-ID|V-228455

Source

• Tenable.com/audits