Overview

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.

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

Disclaimer

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.

Requirements

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:

• 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
• 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

Registry

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 REG_SZ 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

Where:

• 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” instead. 

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

REG file example without user control

Windows Registry Editor Version 5.00  

[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\1x.0\Outlook\Resiliency\AddinList] 
"ADDIN_NAME"="1" 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\Outlook\Addins\ADDIN_NAME] 
"LoadBehavior"=dword:00000003 

[-HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DisabledItems] 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DisabledItems] 

[-HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\CrashingAddinList] 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\CrashingAddinList] 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DoNotDisableAddinList] 
"ADDIN_NAME"=dword:00000001 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\NotificationReminderAddinData] 
"ADDIN_NAME\dtype"=dword:00000000 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\NotificationReminderAddinData] 
"ADDIN_NAME"=dword:967a844d  

REG file example with user control

 
Windows Registry Editor Version 5.00  

[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\1x.0\Outlook\Resiliency\AddinList] 
"ADDIN_NAME"="1" 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\Outlook\Addins\ADDIN_NAME] 
"LoadBehavior"=dword:00000003 

[-HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DisabledItems] 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DisabledItems] 

[-HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\CrashingAddinList] 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\CrashingAddinList] 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DoNotDisableAddinList] 
"ADDIN_NAME"=dword:00000001 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\NotificationReminderAddinData] 
"ADDIN_NAME\dtype"=dword:00000000 

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\NotificationReminderAddinData] 
"ADDIN_NAME"=dword:967a844d   

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

Name            Order   Action      Hive            KeyValue                                    Name            Type        ValueData
ADDIN_NAME        1   Create      HKEY_CURRENT_USER   SOFTWARE\Policies\Microsoft\Office\1x.0\Outlook\Resiliency\AddinList        ADDIN_NAME      REG_SZ  1
LoadBehavior        2   Update      HKEY_CURRENT_USER   SOFTWARE\Microsoft\Office\Outlook\Addins\ADDIN_NAME             LoadBehavior        REG_DWORD   00000003
DisabledItems        3   Delete      HKEY_CURRENT_USER   SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DisabledItems                                 
DisabledItems        4   Create      HKEY_CURRENT_USER   SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DisabledItems                                 
CrashingAddinList    5   Delete      HKEY_CURRENT_USER   SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\CrashingAddinList                                 
CrashingAddinList    6   Create      HKEY_CURRENT_USER   SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\CrashingAddinList                             
ADDIN_NAME        7   Create      HKEY_CURRENT_USER   SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\DoNotDisableAddinList     ADDIN_NAME      REG_DWORD   00000001
ADDIN_NAME        8   Create      HKEY_CURRENT_USER   SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\NotificationReminderAddinData ADDIN_NAME\dtype    REG_DWORD   00000000
ADDIN_NAME        9   Create      HKEY_CURRENT_USER   SOFTWARE\Microsoft\Office\1x.0\Outlook\Resiliency\NotificationReminderAddinData ADDIN_NAME      REG_DWORD   967a844d

PowerShell Script

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
• Enable-AddIn.ps1 -AddinName MyAddIn -AllowUserControl to run the script once, always enable MyAddIn, and allow users to enable or disable the add-in manually from the Outlook user interface

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

param(
[Parameter(Mandatory=$true)]
[string]$AddinName,
[Parameter(Mandatory=$false)]
[switch]$Force,
[Parameter(Mandatory=$false)]
[switch]$AllowUserControl
)

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

function Get-Key
(
[string]$ParentKey,
[string]$KeyName)
{
    for ($i = 0; $i -lt $KeyName.Split("\").Count; $i++)
    {
        try
        {
            $Key = get-item -Path ("{0}:\{1}" -f $ParentKey,($KeyName.split("\")[0..$i] -join "\"))
        }
        catch 
        {
            $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
}
else
{
    try
    {
        $CheckPoint = (Get-Item "HKCU:\Software\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency" | Get-ItemProperty)."CheckPoint" -eq 1
    }
    catch
    {
        $checkPoint = $false
    }
}

if (-not $checkPoint)
{
    if ($AllowUserControl.IsPresent)
    {
        Get-Key -ParentKey HKCU -KeyName "Software\Policies\Microsoft\Office\$OutlookVersion.0\Outlook\Resiliency\AddinList" | Set-ItemProperty -Name $AddinName -Value "2"
    }
    else
    {
        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

Notes

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

References

New in Outlook for developers

Assign User Logon Scripts

Change Log

Date	Author	Description
2nd Aug 2017	Andrei	Original post
31st Oct 2017	Andrei	Corrected the registry entries.
27th Nov 2017	Andrei	Added additional entries to account for crashing add-ins.
10th Dec 2018	Nat	Added additional entries for Outlook 2016.
16th Jan 2019	Andrei	Updated general info to include COM add-ins and explained the reg value that controls the time the add-in stays enabled.
9th Apr 2019	Andrei	Updated reg file examples and PowerShell script to allow user control. Changed the value type for the first value to REG_SZ instead of dword.