As a result of periodic registrations of an existing installation of the Delivery Trust for Outlook plugin, existing user configurations are reset to their default states. These registrations can occur after the plugin has been in a disabled state for an extended duration, been marked as an inactive add-in by Outlook, or 3rd party software/security updates.
It is believed that this issue may only be impacting Exchange environments, though we have not yet been able to confirm this.
Workaround: The only action that can be taken at this time is to reset the configurations to meet your needs.
STATUS - OPEN
This issue is currently with the DEV team who are working to modify the behavior of how the Delivery Trust for Outlook plugin persists user configurations at a local level.