Outlook’s slow add-ins resiliency logic and how to always enable slow add-ins


This post explains how to deploy registry settings that would force Outlook to always load a specific add-in.

The information in this post only applies to slow (VSTO) add-ins in Outlook 2013 or higher.  If Outlook disables your add-in to prevent a crash, this blog post isn't for you.

EDIT: This logic now applies to all COM and VSTO add-ins.


Outlook natively allows add-ins to be enabled one at a time. That's the only official supported way to enable slow add-ins!

This blog post is a best effort to allow users to automate the process at a large scale. This doesn't mean Microsoft CSS is obligated in any way to support this, it's simply a best effort.


Outlook 2013 or 2016.

How it works

Outlook 2013 and 2016's resiliency logic is triggered when one of the criteria enumerated in the Performance criteria for keeping add-ins enabled section of the New in Outlook for developers MSDN article.

Outlook's resiliency logic was introduced with Outlook 2013 and it builds on the foundation set by the resiliency logic in Outlook 2010. As opposed to 2010, Outlook 2013 allows controlling how slow add-ins are handled, giving the users the option to go with the default logic and disable add-ins that take longer than 1 second to load or unload for example, or choose to always enable a certain add-in.

One other aspect to note is that if a VSTO add-in requires a module that is not loaded in Outlook's memory, the first add-in to require that module will incur a "penalty" for each additional module that is loaded. This will apply for all add-ins if a required module is not present, the load time of each module that is required will be added to the load time of the add-in.

In addition to modules, the first add-in to load will incur a penalty for loading the .Net Framework.

In conclusion:

  1. The first add-in to be loaded will have a load time equal to: LOAD_NECESSARY_MODULES [+ LOAD_.NET_FRAMEWORK ] [+ LOAD_VSTO_RUNTIME] + RUN_ADDIN_STARTUP_CODE
  2. All future add-ins to be loaded will have a load time equal to: LOAD_NECESSARY_MODULES + RUN_ADDIN_STARTUP_CODE.

IMPORTANT: Outlook's resiliency logic thresholds are hard coded. For example, the startup time is set to 1000 milliseconds (1 second). This limit cannot be increased, but by following the instructions in this blog post you can tell Outlook to load the add-in despite a load time of more than 1 second. 

Detailed Steps


To work around the resiliency logic, one can use a simple .reg file and add the add-in to the trusted addins list or a Group Policy Object to deploy the same values that would be generated locally to all the users in the domain:

  1. Add a dword entry called ADDIN_NAME with a value data of 1 under HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Office\1x.0\Outlook\Resiliency\AddinList
  2. Set the LoadBehavior (US English spelling!) dword value to 3 under HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\Outlook\Addins\ADDIN_NAME
  3. Delete the HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DisabledItems key
  4. Re-create the HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DisabledItems key
  5. Delete the HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\CrashingAddinList key
  6. Re-create the HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\CrashingAddinList key
  7. Add a dword entry called ADDIN_NAME with a value of 1 under HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DoNotDisableAddinList
  8. Add a dword entry called ADDIN_NAME\dtype with a value of 0 under HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\NotificationReminderAddinData
  9. Add a dword entry called ADDIN_NAME with a value of 967a844d hexadecimal or 2524611661 decimal under HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\NotificationReminderAddinData


  • ADDIN_NAME is the name of the add-in as found under HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\Outlook\Addins\
  • 1x.0 is the office version, for example 15.0 for Office 2013 and 16.0 for Office 2016

NOTE: The value at point 1 will always enable the add-in but it will also prevent the user from controlling the add-in load behaviour. To allow users to control the add-in (enable or disable it from the Outlook user interface), set a value data of 2 (or dword:00000002 for the reg file) instead.  

NOTE: The value at point 9 always enables your add-in until Saturday, January 1st 2050 at 1:01:01 AM.

Here is a REG file example:

Windows Registry Editor Version 5.00

GPO (Group Policy Object)

As far as group policy objects go, please find below the procedure:

  1. Open the Group Policy Management console on a domain controller
  2. Navigate to the domain node, right click it and select Create a GPO in this domain, and Link it here
  3. Give the GPO the desired name
  4. Right click the newly created GPO and click on Edit
  5. In the Group Policy Management Editor, expand Preferences under User Configuration
  6. Afterwards expand Windows Settings
  7. Right click Registry and create the following 9 entries:


Please find below a PowerShell script sample that sets the above registry settings. Please save the script block as Enable-AddIn.ps1.

The syntax to run the script is Enable-AddIn.ps1 -AddinName ADDIN_NAME, where add-in name is the name of the add-in to always enable. The script will run once and set a registry value as a checkpoint. To force it to run again you can use the -Force parameter.

For example:

  • Enable-AddIn.ps1 -AddinName MyAddIn to run the script once and always enable MyAddIn
  • Enable-AddIn.ps1 -AddinName MyAddIn -Force to always run the script and enable MyAddIn

For more information on how to configure a script via GPO, please check the following article: Assign User Logon Scripts


$AddinList = $null
$CrashingAddinList = $null
$DoNotDisableAddinList = $null

function Get-Key
     for ($i = 0; $i -lt $KeyName.Split("\").Count; $i++)
           $Key = get-item -Path ("{0}:\{1}" -f $ParentKey,($KeyName.split("\")[0..$i] -join "\"))
           $Key = new-item -Path ("{0}:\{1}" -f $ParentKey,($KeyName.split("\")[0..$i] -join "\"))
     return $Key

$ErrorActionPreference = [System.Management.Automation.ActionPreference]::Stop
$OutlookVersion = (Get-ItemProperty HKLM:\SOFTWARE\Classes\Outlook.Application\CurVer)."(default)".Replace("Outlook.Application.", "")

if ($Force)
     $checkPoint = $null
        $CheckPoint = (Get-Item "HKCU:\Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency" | Get-ItemProperty)."CheckPoint" -eq 1
        $checkPoint = $false

if (-not $checkPoint)
     Get-Key -ParentKey HKCU -KeyName "Software\Policies\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\AddinList" | Set-ItemProperty -Name $AddinName -Value 1
     Get-Key -ParentKey HKCU -KeyName "Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\DoNotDisableAddinList" | Set-ItemProperty -Name $AddinName -Value 1
     Get-Key -ParentKey HKCU -KeyName "Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\DisabledItems" | Remove-Item
     Get-Key -ParentKey HKCU -KeyName "Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\DisabledItems" | Out-Null
     Get-Key -ParentKey HKCU -KeyName "Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\CrashingAddinList" | Remove-Item
     Get-Key -ParentKey HKCU -KeyName "Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\CrashingAddinList" | Out-Null
     Get-Key -ParentKey HKCU -KeyName "Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\NotificationReminderAddinData" | Set-ItemProperty -Name ([string]::Format("{0}\dtype",$AddinName)) -Value 2
     Get-Key -ParentKey HKCU -KeyName "Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\NotificationReminderAddinData" | Set-ItemProperty -Name $AddinName -Value 2524611661
     Get-Item "HKCU:\Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency" | Set-ItemProperty -Name "CheckPoint" -Value 1

NOTE: To allow users to control the add-in (enable or disable it from the Outlook user interface), replace "-value 1" with "-value 2" in the following script line: Get-Key -ParentKey HKCU -KeyName "Software\Policies\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\AddinList" | Set-ItemProperty -Name $AddinName -Value 1


Please follow the instructions carefully and for best results use the PowerShell script above.


New in Outlook for developers

Assign User Logon Scripts

Assign User Logon Scripts

Change Log

Date Author Type Description
02/08/2017 Andrei Ghita Original
31/10/2017 Andrei Ghita Update Corrected the registry entries.
27/11/2017 Andrei Ghita Update Added additional entries to account for crashing add-ins.
10/12/2018 Natercia Gomes Update Added additional entries for Outlook 2016.
16/01/2019 Andrei Ghita Update Updated general info to include COM add-ins and explained the reg value that controls the time the add-in stays enabled.
Comments (21)
  1. Nick Botica says:

    Will this require the user to close and open Outlook?
    What if I setup GPO to delete the SOFTWARE\Microsoft\Office\1x.0\Outlook\AddInLoadTimes ADDIN_NAME value.
    And delete the SOFTWARE\Microsoft\Office\1x.0\Outlook\Addins\ADDIN_NAME key.

    Then Outlook won’t get 5 start time readings and have any reason to disable it?

    What does “Software\Policies\Microsoft\Office\1x.0\Outlook\Resiliency\AddinList​” do exactly? Will this stop Outlook disabling the addin no matter what (well due to loading times anyway)?

  2. Nick Botica says:

    In the table at the bottom the Key path doesn’t have the Outlook version. Should it? All your other examples do.

    1. Andrei Ghita says:

      You are correct, ti should include the Office version key.

  3. Jarrod says:

    I believe ADDIN_NAME should be a String (REG_SZ) value “1” instead of a DWORD as follows?


    1. Andrei Ghita says:

      Hmmm, not according to MSDN (https://msdn.microsoft.com/en-us/vba/outlook-vba/articles/support-for-keeping-add-ins-enabled) but I’ll double check and update the post if needed.

    2. Yes, Jarrod is correct. The value in HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\1x.0\Outlook\Resiliency\AddinList MUST be a REG_SZ. It will not work if it is a DWORD. I tested it as a DWORD even though all of my other values there are strings. I confirmed that it must be a REG_SZ.

      1. Andrei Ghita says:

        I’ve checked the source and you guys are right, it should be a string.


  4. Eric Shao says:

    Hi Andrei, “If Outlook disables your add-in to prevent a crash, this blog post isn’t for you.” Do you have another post to deal with this kind of situation? Is it possible to prevent Outlook from disabling my add-in which causes outlook to crash?

    1. Andrei Ghita says:

      Hi Eric,

      Have a look at the “Troubleshooting Startup Errors by Using a Log File and Error Messages” section in https://msdn.microsoft.com/en-us/library/ms269003.aspx and set VSTO_SUPPRESSDISPLAYALERTS to 0 to allow for a pop-up that displays information on any exceptions that might occur at load time.

      If you do get a pop-up, be sure to click on details, copy the exception details and get back to me with the details.

      There isn’t a guide on troubleshooting crashing add-ins. Unless there’s an obvious reason for the crash, we usually end up debugging Outlook and the add-in to understand why it crashes.


  5. anovosel says:

    Does article descriptions “Outlook’s slow add-ins resiliency logic and how to always enable slow add-ins” will be OK for new Windows 10 Enterprise Version 1809 release and OS build 17763.253 and Outlook version


    1. Andrei Ghita says:

      Hi Alex,

      Yes, it should work for all Outlook builds ranging from 2013 to 2019. The OS version isn’t relevant or it shouldn’t be.


  6. smallmc says:

    When I execute the PowerShell script I get the following error. What permission is required to use the provided script?

    This was executed as the user who is running Outlook.

    new-item : Requested registry access is not allowed.
    At C:\path\to\script\Enable-Addin.ps1:25 char:19
    + … $Key = new-item -Path (“{0}:\{1}” -f $ParentKey,($KeyName.split( …
    + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo : PermissionDenied: (HKEY_CURRENT_US…ce\16.0\Outlook:String) [New-Item], SecurityException
    + FullyQualifiedErrorId : System.Security.SecurityException,Microsoft.PowerShell.Commands.NewItemCommand

    1. Andrei Ghita says:

      Your users will effectively need to have write access to the HKEY_CURRENT_USER hive. All users should be able to write under their own registry hive so you might need to take this up with your domain admins to see if there are any GPOs preventing the users from writing to HKCU.

  7. J_T- says:

    Hi Andrei,
    This is very helpful.
    What is the purpose of checkpoint value ? What does this value represent? (Get-Item “HKCU:\Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency” | Get-ItemProperty).”CheckPoint” -eq 1

  8. Hello,
    We are seeing cases where the LoadBehavior key is not getting updated, but rather added a 2nd time. Basically, in HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\Outlook\Addins\ADDIN_NAME, there are 2 LoadBehavior entries, one with a value of 2 and one with a value of 3, and it appears that Outlook often (if not always) picks 2, so the addin stays disabled.

    Is anyone else seeing this behaviour? I’m curious to see what was done to address this.

    I’m going to try a Replace action instead of Update to see if it helps.


  9. jedwards73 says:

    I tried adding the keys using registry file. Everything worked except this line.


    That one doesn’t get created.

    The one below works though.


    Just the “dtype” one doesn’t get created. I can’t find any difference between the two except maybe it doesn’t like the \dtype part?

  10. MohSyed says:

    Is there a way to prevent disablement for all the users that will logon to the system possibly using a system key (HKLM). In an enterprise environment the installer may be running in the system context. I could not find a way to use installation tools like Wix to configure installer to setup hkcu based values for all possible users that will logon to the system in future (think Active Setup may offer alternative). Anybody has any suggestions?

  11. Why is this process above necessary if there is a GPO setting
    User\Policies\Admin Tempates\Outlook 2016\Miscellaneous\List of managed add-ins\ ?
    If you add an add-in to this list it apparently forces it to load.
    BUT the text on the GPO states –
    ” 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. “, which if you read it, appears to be irrelevant – if the add-in is disabled by the GPO and therefore will not load then it will not be subject to any possible disablement by the outlook slow add-in resilience. However if there is a typo in the amdl file and has been there for over 5 years where the first use of the word “disabled” is replaced with Enabled, then the sentence makes sense and a by product of this would be to force the add-in to load always even if Outlook detects a resilience or slow performance issue. Is it possible to clarify if there is a typo in the amdl file and this setting has a useful side effect

    1. Stephen Kish says:

      Good point Mike. If the wording in the description contains a typo, the List of managed add-ins GP may be part of the solution, assuming it ‘cleans up’ (re-enables) add-ins that users have already (un)intentionally disabled prior to the GP being created and applied.

    2. JohnForth says:

      Does the Group Policy Setting prevent Outlook from deactivating the add-in if it crashes while opening Outlook?

    3. Andrei Ghita says:

      The process as you call it does more than what the GPO does. It cleans up various reg keys and it does more than what the Managed Add-ins list does.

      This post is intended to help not to hinder and if you feel there is an easier way to deal with re-enabling add-ins and keeping them enabled you should definitely use the easiest way for you.


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