A default deployment of the add-in allows users to disable the add-in in Microsoft Outlook or other Microsoft Office applications manually. 

Admins can override this setting by enabling the relevant group policy setting. This setting will prevent users from manually disabling the add-in. 

To prevent users from disabling the Outlook add-in, follow the steps below:

1. Open the Group Policy Editor and check that the Office Administrative Templates are installed. These can be located in User Configuration Administrative Templates Microsoft Outlook[YEAR] Miscellaneous.
2. If they are not installed, the administrative templates for Microsoft are available at the below URLs:
   • Office 2016: https://www.microsoft.com/en-us/download/details.aspx?id=49030
   • Office 2013: https://www.microsoft.com/en-gb/download/details.aspx?Id=35554
3. Ensure the "List of managed add-ins" setting is set to Enabled.
4. Select Show... in the "List of managed add-ins".
5. Enter "Egress.Switch" and set the value to 1. This action will ensure the add-in cannot be disabled.
6. Alternatively, it's possible to deploy the registry key via Group Policy (GPO). The Registry Key type should be REG_SZ.