Information
This policy setting controls how Outlook warns users about messages with invalid digital signatures.
The recommended state for this setting is: Enabled: Always warn about invalid signatures
If users are not notified about invalid signatures, it might prevent the user from detecting a fraudulent signature sent by a malicious user.
Solution
To establish the recommended state via configuration profiles, set the following Settings Catalog path to Enabled: Always warn about invalid signatures :
Microsoft Outlook 2016\Security\Security Form Settings\Outlook Security Mode > Signature Warning
Important: For this setting to apply, the
Outlook Security Mode
setting must be enabled in
Microsoft Outlook 2016\Security\Security Form Settings
with Use Outlook Security Group Policy selected, as set in this benchmark.
Impact:
None - This is the default behavior.
Enabling this setting could cause some disruptions for Outlook users who receive a lot of e-mail messages signed with invalid signatures. These users will see a warning dialog box every time they open a signed e-mail message.