M365 Changelog: Migrate your Outlook COM/VSTO add-ins to web add-ins model supported in the new Outlook for Windows

MC528299 – Microsoft recently announced the expansion of new Outlook for Windows to Current Channel users in April 2023, with the goal of providing a unified, modern and robust Outlook experience across desktop and web.

One of the top feedback items Microsoft hears today is that Outlook works differently on different platforms, making it hard for tenants to manage, and for users to seamlessly use it across endpoints. With the new Outlook for Windows, our goal is to bring rapid access to new features through a shared codebase and ensure platform consistency and robustness.

In line with this, Microsoft is committed to providing a unified and reliable experience for apps built on top of Outlook, and hence, only web add-ins will be supported in this new version of Outlook for Windows.

Please note that COM/VSTO add-ins will not be supported in the new Outlook for Windows but will continue to work in classic Outlook for Windows. During the transition, both the new Outlook and classic Outlook will get the latest features for Outlook web add-ins.

The web add-in platform provides a robust experience and an easy way to deploy add-ins across Outlook endpoints. It continues to be an area of constant investment at Microsoft, and Microsoft is strengthening the platform even further so that most COM/VSTO add-in capabilities are supported.

To have your Add-in(s) working in the new Outlook Microsoft recommends you to: 

  • Start migrating any COM/VSTO add-ins that your organization uses, to web add-ins. You can check installed COM/VSTO add-ins by following the instructions here. This will ensure that your users continue to have support for critical add-ins in the new Outlook version. Refer to this article for more details including a list of common Outlook extensibility scenarios and the feasibility of its implementation as web add-ins: Develop Outlook add-ins for the new Outlook on Windows (preview) – Office Add-ins | Microsoft Learn
  • Reach out to your 3rd party COM/VSTO add-in partners to develop a web Add-in equivalent if one doesn’t already exist.
  • Let us know if there are any web add-in platform gaps preventing you from moving your COM add-ins to web at https://aka.ms/DevNewOutlook.
  • Test any web add-ins you use today in the new Outlook for Windows and raise a Github ticket if you find any issues.

Note: If you require to hide the New Outlook for Windows toggle for users, you can follow the instructions for Outlook here – Release Notes for Beta Channel – Office release notes | Microsoft Learn