📋 Outlook Add-In (classic): Prevent automatic deactivation (Registry)

This article provides administrators with instructions for diagnosing and reactivating the Outlook Add-In if it is automatically disabled by Microsoft Outlook.

Microsoft Outlook can automatically disable add-ins if they increase Outlook's startup time or cause errors. In some cases, the FTAPI Outlook Add-In remains disabled even after a reinstallation. This can be caused by specific registry entries or Group Policy Objects (GPOs) that prevent the add-in from loading.

Possible causes

Outlook classifies the add-in as performance-degrading: If the FTAPI Outlook Add-In takes too long to load, it may be added to Outlook's "ignore list".
Outlook permanently disables the add-in: A registry value may prevent the add-in from loading again.
Corporate policies (GPOs) block the add-in: A Group Policy Object (GPO) may prevent the FTAPI Outlook Add-In from loading. In this case, changes can only be made by the IT department.

Step-by-step guide for reactivation

1. Checking the Outlook Resiliency list

If the FTAPI Outlook Add-In has been classified as problematic by Outlook, it may have been saved in the so-called "Resiliency" list. Check the following registry path:

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Resiliency

If there are entries related to the FTAPI Outlook Add-In, you can remove them to allow for reactivation. If you are unsure, contact your IT department before making changes to the registry.

2. Checking the “LoadBehavior” value

If the FTAPI Outlook Add-In is visible in the list of installed add-ins but cannot be activated, check the following registry path:

HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\Addins\FTAPI.AddIn\LoadBehavior

The value should be set to 3. If Outlook automatically resets this value to 2, there may be an issue with the add-in configuration or the system environment. In this case, we recommend checking the Windows Event Viewer for errors or creating a support request.

3. Protection against automatic deactivation (DoNotDisableAddinList)

If the FTAPI Outlook Add-In is running stably, it can be protected from automatic deactivation by Outlook. To do this, it must be added to the so-called “DoNotDisableAddinList”. This setting can be configured via the Windows Registry:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Office\16.0\Outlook\Resiliency\DoNotDisableAddinList

Create a new DWORD value in this path with the name of the FTAPI Outlook Add-In and set the value to 1. This prevents Outlook from automatically disabling the add-in.

Note: Changes to the Windows Registry should only be made by IT administrators or experienced users. Create a backup of the registry beforehand.

Additional notes

If the problem persists, check the Windows Event Viewer under Windows Logs > Application for errors related to the FTAPI Outlook Add-In.
If the add-in is displayed as disabled in Outlook under "Manage Add-ins", you can try to reactivate it manually there.
If the FTAPI Outlook Add-In remains disabled despite manual activation, a Group Policy in your corporate environment could be the cause. In this case, contact your IT department to check if a corresponding policy is blocking the add-in.