Support for Keeping Add-ins Enabled

Programs in Office 2013 and later versions provide add-in resiliency, meaning that apps will disable an add-in if it performs slowly. However, you can re-enable add-ins and prevent add-ins from being auto-disabled by other Office programs.

Preventing add-ins from being disabled

While most add-ins will not be disabled by the add-in disabling feature, you don't want your add-in to be disabled consistently.

Below are some suggestions for improving add-in performance:

  • Prefer native COM add-ins over managed add-ins since managed add-ins must incur the overhead of loading the .NET Framework during Outlook startup.

  • If you have long-running tasks such as making an expensive connection to a database, defer those tasks to occur after startup.

  • If possible, cache data locally rather than making expensive network calls during the FolderSwitch and BeforeFolderSwitch events of an explorer, or Open events of an item.

  • Be aware that all calls to the Outlook object model execute on Outlook's main foreground thread. Avoid making long-running Outlook object model calls if possible.

  • In Outlook 2013, calls to the Outlook object model return E_RPC_WRONG_THREAD when the Outlook object model is called from a background thread.

  • Polling is an expensive operation, so always prefer an event-driven model over polling.

System Administrator control over add-ins

The user has control over which add-ins run on their computer. For system administrators, Outlook 2013 provides an enhanced level of control over add-ins using group policy. Group policy will always override user settings and users are prevented from changing add-in settings for add-ins that have been configured by the group policy "List of Managed Add-ins".

The registry keys and settings are described in the following tables:

Name Description
Key HKCU\Software\Policies\Microsoft\Office\15.0\Outlook\Resiliency\AddinList
Description This policy setting allows you to specify the list of managed add-ins are always enabled, always disabled (blocked), or configurable by the user. Note: Here, the term "managed" refers to add-ins that are handled by the group policy, and does not relate to add-ins being developed in managed programming languages.
DWORD ProgID of the add-in
Values Specify the value as follows:0 = always disabled (blocked)1 = always enabled2 = configurable by the user and not blocked by the "Block all unmanaged add-ins" policy setting when enabled


  • Use the Registry Editor on the client computer where the add-in is installed, in order to obtain the ProgID for an add-in: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Outlook\Addins or HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\Outlook\Addins

  • If you disable or do not enable this policy setting, the list of managed add-ins will be deleted. If the "Block all unmanaged add-ins" policy setting is enabled, then all add-ins are blocked.

  • Add-ins that are disabled by this policy will never be disabled by the Outlook add-in disabling feature, which disables add-ins for performance, resiliency, or reliability reasons.

  • If the user chooses "Always enable this add-in", the registry is updated to include details about the add-in that is to be exempted from the automatic disabling feature.

Name Description
Key HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\Resiliency\DoNotDisableAddinList
DWORD ProgID of the add-in
Values Hex value between 1 and A indicating the reason the add-in was originally disabled:
0x00000001 Boot load (LoadBehavior = 3)
0x00000002 Demand load (LoadBehavior = 9)
0x00000003 Crash
0x00000004 Handling FolderSwitch event
0x00000005 Handling BeforeFolderSwitch event
0x00000006 Item Open
0x00000007 Iteration Count
0x00000008 Shutdown
0x00000009 Crash, but not disabled because add-in is in the allow list
0x0000000A Crash, but not disabled because user selected no in disable dialog
Note: The x.0 placeholder represents the version of Office (16.0 = Office 2016, 15.0 = Office 2013).

Note: If you re-enable an add-in that caused a performance problem at one time, users may experience performance problems in the future in the Office program for which the add-in is loaded.

To block add-ins that are not managed by this policy setting, you must also configure the "Block all unmanaged add-ins" policy setting.

See also