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Installing the add-in

There are two install paths: admin-driven (everyone in the tenant gets it) and user-driven (each user adds it themselves from Get Add-ins).

  1. In the portal, open Deployment.
  2. Under Outlook Add-In, copy the unified manifest ZIP URL (or download the file).
  3. In Microsoft 365 admin centre → Integrated Apps, click Upload custom apps → Office add-in → As ZIP and paste the URL (or upload the file you downloaded).
  4. Pick an assignment: All users (default), Specific users / groups, or Catalog only.
  5. Wait ~12 hours for Office to propagate the assignment to mailboxes.

End users will see a new ribbon button labelled Quarantined messages the next time they open Outlook.

User-driven (testing, or self-install tenants)​

If you skipped step 4 above (or chose Catalog only), end users can install themselves:

  1. In Outlook, open any message.
  2. Click Get Add-ins on the toolbar.
  3. Search for Defender Quarantine under My organization.
  4. Click Add.

Coming soon: Microsoft AppSource​

When our AppSource listing certifies, the install URL changes to a one-click marketplace deep link and the manifest URL above is no longer needed. The portal will swap the sideload card for the AppSource link automatically.

Confirming it worked​

The fastest way to verify: ask one user to open Outlook, find the add-in, and click any quarantined message (if they have one). Then refresh the portal's Observed Versions card — you should see that user appear within seconds with the correct version + platform icon.

→ Next: Using the add-in walks through what an end user sees.