If you rely on a COM add-in in classic Outlook, you may have discovered that the new Outlook for Windows does not load these add-ins at all. Microsoft built the new Outlook on a web-based platform that lacks the COM infrastructure used by older add-ins. This article explains why COM add-ins are blocked and shows you the practical alternatives that actually work in the new Outlook.
Key Takeaways: New Outlook COM Add-in Limitations
- Outlook Web Add-ins (Office Store): Install web-based add-ins from the Office Store or your admin center that work in both new and classic Outlook.
- File > Options > Add-ins > Manage COM Add-ins: This menu is missing in new Outlook because the COM layer does not exist.
- Exchange Web Services (EWS) or Microsoft Graph API: Developers must rewrite COM add-ins as web add-ins using these APIs for new Outlook compatibility.
Why New Outlook Blocks COM Add-ins
Classic Outlook uses a COM-based architecture that loads add-ins as compiled DLL files directly into the Outlook process. New Outlook is built on the Outlook on the web engine, which runs in a sandboxed web environment. This architecture has no mechanism to load native Windows DLLs. Microsoft also removed the COM add-in loading code to improve stability and security. COM add-ins can crash Outlook or slow it down because they share the same memory space. In the new Outlook, only JavaScript-based web add-ins are allowed because they run in an isolated browser sandbox.
The COM add-in tab in File > Options > Add-ins does not appear in new Outlook. If you open the classic Outlook and see a list of COM add-ins under Active Application Add-ins, those will not transfer to the new Outlook. Any add-in that appears as a Type “COM Add-in” in classic Outlook is incompatible.
How to Check if Your Add-in Is COM-based
Open classic Outlook. Go to File > Options > Add-ins. Look at the Type column next to each add-in in the Active Application Add-ins list. If the type says “COM Add-in,” it will not work in new Outlook. If the type says “Outlook Web Add-in” or “App for Office,” it will work in both versions.
Steps to Replace a COM Add-in in New Outlook
Follow these steps to find and install a compatible web add-in that replaces your COM add-in functionality.
- Identify the missing feature
Write down exactly what your COM add-in did. Examples: send encrypted email, integrate with a CRM system, or add a custom meeting scheduling tool. - Open the new Outlook add-in store
In new Outlook, click the Get Add-ins button on the Home ribbon. If you do not see this button, click the three dots (More commands) and select Get Add-ins. - Search for a replacement add-in
In the add-in store, type the name of your vendor or the feature you need. Many popular COM add-in vendors have released web add-in versions. Examples: Evernote, Trello, DocuSign, and Zoom all have web add-ins for Outlook. - Install the web add-in
Click the Add button next to the add-in. Review the permissions it requests. Click Continue to install. The add-in appears in the Home ribbon or in the add-in task pane. - Test the add-in in new Outlook
Open an email or meeting and click the add-in icon. Verify that the core feature works. If the add-in does not appear, restart new Outlook and check again.
If No Web Add-in Exists for Your COM Add-in
Some legacy COM add-ins do not have a web add-in version. In that case, you have two options. Option one: continue using classic Outlook alongside new Outlook. You can run both versions on the same computer. Option two: ask your IT department or the add-in vendor to create a web add-in using the Microsoft 365 Developer Program. Web add-ins use the Office JavaScript API and the Microsoft Graph API instead of COM.
Common Issues When Switching from COM to Web Add-ins
The add-in I installed does not appear in the ribbon
Web add-ins only appear when you open a message, appointment, or meeting that matches the add-in’s activation rules. For example, a CRM add-in may only activate when the email contains a contact name. Check the add-in documentation for activation conditions. You can also click the three dots in the ribbon and select the add-in from the overflow menu.
My COM add-in vendor says they will not release a web version
If the vendor has no plans to support new Outlook, you must either keep classic Outlook or find a competing web add-in. Classic Outlook is still supported and receives security updates. You can pin classic Outlook to your taskbar and use new Outlook only for basic email tasks. To switch between versions, click the toggle in the upper-right corner of new Outlook.
The web add-in is slower than the old COM add-in
Web add-ins run in a sandboxed browser process, which adds a small delay when loading. This is normal. If the add-in feels unusably slow, check your internet connection because web add-ins require network access. Some add-ins cache data locally to improve speed. Contact the add-in developer to report performance issues.
COM Add-in vs Web Add-in: Key Differences
| Item | COM Add-in | Web Add-in |
|---|---|---|
| Architecture | Native DLL loaded into Outlook process | JavaScript running in a sandboxed browser |
| Compatibility | Classic Outlook only | New Outlook, classic Outlook, Outlook on the web |
| Installation | Manual installer or MSI file | Office Store or centralized deployment |
| Security | Full access to Windows and Outlook memory | Limited to API permissions granted by user |
| Performance | Can slow down or crash Outlook | Isolated process, less impact on Outlook stability |
| Update method | Vendor-provided update installer | Automatic update through Office Store or admin center |
If you must keep a COM add-in, switch to classic Outlook by turning off the new Outlook toggle. Microsoft will support classic Outlook through at least 2029. For new deployments, always choose web add-ins to ensure compatibility with the new Outlook.