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.

Following are some suggestions for improving add-in performance:

  • Prefer native COM add-ins over managed add-ins because 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. Beginning with Office 2013, system administrators can configure an enhanced level of control for add-ins by 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.

For Outlook, the registry keys and settings are described in the following tables.

Name Description
Key Office 2013:

Office 2016/2019/365:
Description This policy setting allows you to specify the list of managed add-ins that 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.
String ProgID of the add-in
Values Specify the value as follows:
0 = always disabled (blocked)
1 = always enabled
2 = configurable by the user and not blocked by the Block all unmanaged add-ins policy setting when enabled.


To obtain the ProgID for an add-in, use the Windows Registry Editor on the client computer where the add-in is installed. Copy the registry key names under found: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office<application>\Addins or HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office<application>\Addins. Registry key names are case sensitive.

  • If you disable or don't 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
Description This Key prevents add-ins you specify from being disabled by the add-in disabling feature.
DWORD ProgID of the add-in
Values A 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 2016/2019/365, 15.0 = Office 2013).


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

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