Classic Outlook COM Add-ins Missing in New Outlook: Best Replacement

You upgraded to the new Outlook for Windows and discovered that your trusted COM add-ins no longer appear on the ribbon or in the add-in manager. The new Outlook uses a web-based platform that does not support traditional Component Object Model add-ins built for the classic desktop client. This article explains why COM add-ins are missing, lists the built-in and web-based alternatives that replace their core functions, and shows you how to install the correct replacements.

Why COM Add-ins Do Not Work in the New Outlook

The new Outlook is built on Outlook for the web technology. It uses a web-based rendering engine and a JavaScript API layer called Office.js. COM add-ins are compiled binaries that load directly into the classic Outlook process. The web-based architecture of the new Outlook cannot load these binaries. Microsoft designed the new Outlook to support only web add-ins and Exchange Web Services-based integrations.

When you open the new Outlook, you may see a yellow notification bar that says “This add-in is no longer available” or the add-in simply does not appear in the ribbon. The add-in manager in the new Outlook shows only web add-ins. Any COM add-in you installed in the classic Outlook is invisible to the new client.

What Happens to Your Existing COM Add-in Data

Your COM add-in data such as templates, custom properties, and configuration settings remain in your classic Outlook profile. The new Outlook does not read or migrate this data. If you switch back to the classic Outlook, the COM add-in and its data still work. The data is not lost, but it is not accessible in the new Outlook until you install a web-based replacement that connects to the same service.

Steps to Find and Install Replacement Web Add-ins

1. List every COM add-in you use
   Open classic Outlook. Go to File > Options > Add-ins. In the Manage drop-down at the bottom, select COM Add-ins and click Go. Write down the name and publisher of each add-in in the list.
2. Search for a web-based equivalent in AppSource
   In the new Outlook, click Get Add-ins in the Home tab ribbon. The Add-ins dialog opens to the Microsoft AppSource store. Type the add-in name or function into the search box. For example, search “Adobe Sign” or “DocuSign” if you used a signature COM add-in.
3. Install the web add-in from the store
   Click the add-in tile in the search results. Review the permissions and data access statements. Click Add to install. The add-in appears in the ribbon or in the Add-ins pane on the right side of the reading pane.
4. Install add-ins deployed by your IT admin
   If your organization uses centralized deployment, your IT admin must upload the add-in manifest to the Microsoft 365 admin center under Settings > Integrated apps. After the admin deploys the add-in, it appears automatically in the new Outlook for all assigned users.
5. Configure Power Automate for automation tasks
   For COM add-ins that performed automated workflows such as saving attachments to a folder or sending follow-up reminders, create a flow in Power Automate. Select the Outlook trigger and the action that matches your original automation. For example, use “When a new email arrives” trigger and “Create file” action for OneDrive or SharePoint.

How to Check if a Web Add-in Is Already Installed

In the new Outlook, click the three dots (More actions) in the ribbon and select Get Add-ins. The Add-ins dialog shows two tabs: Admin managed and Store. The Admin managed tab lists add-ins deployed by your organization. The Store tab lists add-ins you installed yourself. If you see the add-in in either list, it is already available.

Common Issues When Replacing COM Add-ins

The web add-in does not have the same features as my COM add-in

Many COM add-ins had deep integration with the Outlook object model, such as reading all mailbox folders or modifying email properties before sending. Web add-ins run in a sandboxed browser environment and cannot access the same level of data. Check the add-in documentation to confirm its capabilities. If the feature is not available, use Power Automate or a custom script in Exchange Online PowerShell as a workaround.

I cannot find any web add-in that replaces my COM add-in

Some niche COM add-ins from small vendors have not been ported to the web add-in platform. Contact the vendor and ask if they have a web add-in version. If they do not, you have three options: stay on classic Outlook, build a custom web add-in using the Office Yeoman generator, or switch to a different tool that provides the same functionality through a standalone application.

The web add-in slows down the new Outlook

Web add-ins run in a separate browser process. If an add-in uses excessive CPU or memory, it can slow down the entire application. Disable the add-in by going to Get Add-ins, clicking the three dots next to the add-in name, and selecting Remove. Reinstall only add-ins that you use daily.

COM Add-in Functions and Their Web-based Replacements

Function	Classic COM Add-in Example	Web-based Replacement
Email signature management	Exclaimer, CodeTwo	Exclaimer Cloud, CodeTwo Exchange Rules
CRM integration	Dynamics 365 for Outlook, Salesforce for Outlook	Dynamics 365 App for Outlook, Salesforce Inbox
Document generation	PandaDoc, Conga	PandaDoc web add-in, Conga web add-in
Email archiving	Barracuda, Mimecast	Barracuda Cloud Archiving, Mimecast web add-in
Spam filtering	SpamAssassin, GFI MailEssentials	Exchange Online Protection, third-party cloud filters

Conclusion

You now know why COM add-ins do not load in the new Outlook and how to find equivalent web add-ins in AppSource. Start by listing your current COM add-ins, then search for each function in the store. For automation tasks that previously required a COM add-in, use Power Automate with the Outlook connector. If a web replacement does not exist, contact the vendor or plan to stay on classic Outlook until a web version is available. You can switch between the new Outlook and classic Outlook at any time using the toggle in the top-right corner of the new Outlook window.