Send all signed messages as clear signed messages must be configured.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-228455	DTOO264	SV-228455r508021_rule		Medium

Description
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.

Description

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.

STIG	Date
Microsoft Outlook 2016 Security Technical Implementation Guide	2022-03-11

Details

Check Text ( C-30688r497687_chk )
Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Send all signed messages as clear signed messages" is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\16.0\outlook\security Criteria: If the value ClearSign is REG_DWORD = 1, this is not a finding.

Check Text ( C-30688r497687_chk )

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Send all signed messages as clear signed messages" is set to "Enabled".

Procedure: Use the Windows Registry Editor to navigate to the following key:

HKCU\Software\Policies\Microsoft\Office\16.0\outlook\security

Criteria: If the value ClearSign is REG_DWORD = 1, this is not a finding.

Fix Text (F-30673r497688_fix)
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Send all signed messages as clear signed messages" to "Enabled".