Ever since the modern add-ins were introduced in Outlook, one of the most requested features has been the ability to activate an add-in in a shared mailbox. Although documented as preview mode, many people have been struggling to get access to this feature in order to test in their own environment.
Office Add-ins for Outlook (Outlook Web Add-ins) are composed of 2 parts: a web application – written in the web development language of choice of the developer; and a manifest file – in XML format, declaring the rules for which Outlook will activate the add-in.
The functionality is currently in preview, so in order to allow add-is to be activated for shared mailboxes you must run the Click-to-run monthly channel insiders fast version of Office.
To check if you are running the Insider version, in the File menu, click on Office Account and check the About Outlook information. The screenshot below shows the version information for the Office Insider build 1904.
Installing an Office Insider build
If you’re not running an Office Insider build, your add-in won’t activate for shared mailboxes.
In order to install Office Insider, you will need to update the registry information for the local machine as indicated below:
NOTE: registry changes should be performed with extreme caution, and a registry backup should be performed prior to changes
- Run Regedit.exe
- Create the following key if it doesn’t exist: Key: HKLM\SOFTWARE\Policies\Microsoft\office\16.0\common\officeupdate
- Create a REG_SZ value named updatebranch and set the value data to InsiderFast
- Restart all running Office applications
- Run Outlook.exe
- In the File menu, click on Office Account
- Click on Update Options and select Update Now
NOTE: The values accepted for the updatebranch value are: InsiderFast, FirstReleaseCurrent, Current, FirstReleaseDeferred, Deferred
Sample .reg file:
Should you wish to automate this for multiple users by means of importing a reg file, please find below a sample that you can save to disk as a .reg file and run in order to import the settings:
Windows Registry Editor Version 5.00 [HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Common\OfficeUpdate] "UpdateBranch"="InsiderFast"
Adding Shared Folders support to your add-in
Once you have the Office Insider build installed, you need to enable shared folders support in your add-in as indicated in the SupportsSharedFolders element documentation.
A common error when updating the manifest is to create the SupportsSharedFolders XML tag under version Overrides 1.0 section on the manifest, which will not pass schema validation, preventing from uploading the manifest. This XML Tag must be created inside the DesktopFormFactor inside VersionOverrides 1.1, only this way the add-in will be activated.
A sample manifest can be found at https://github.com/developermessaging/Angular_AddIn/blob/master/manifest.xml
Once you’ve enabled shared folders support, your add-in should successfully activate for shared mailboxes.
IMPORTANT: Shared Folders support is preview functionality and should not be used in production environments.