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Outlook stopped rendering inside Teams

Maksym Hryshakov 145 Reputation points
2026-05-04T08:27:41.26+00:00

We have noticed that our Outlook links stopped rendering inside Teams.

We render them as channel tabs using our custom Teams app. It was working until previous week. But then in the network tab of the browser we started seeing error in the Status column. The errors says: '(blocked:origin)'.

The url we are trying to render is https://outlook.cloud.microsoft/groups/*******/*****/mail

After investigation we found that outlook response headers contains '**content-security-policy'.
**Inside that header there is this value. 

frame-ancestors 'self' teams.microsoft.com

But the Teams domain now is 'teams.cloud.microsoft' which is not included in the frame ancestors from above. And that's why it is not rendered.

Can you please add new domain to frame-ancestors?

Microsoft Teams | Development
Microsoft Teams | Development

Building, integrating, or customizing apps and workflows within Microsoft Teams using developer tools and APIs

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  1. Jayden-P 20,415 Reputation points Microsoft External Staff Moderator
    2026-05-04T09:39:16.5633333+00:00

    Hi @Maksym Hryshakov

    Please note that this forum is not Microsoft Support; it is a community for users to help one another. Therefore, moderators in this forum cannot perform the inquiry you requested since we do not have access to back-end system.

    As a forum moderator, I’m here to help guide discussions and share insights based on Microsoft documentation and community knowledge. Although I don’t have direct access to the backend system, I’ll do my best to support you with practical steps and point you to the appropriate resources.

    After doing some research, I found this article might help: Requirements for Building Tabs - Teams | Microsoft Learn

    You are right about Microsoft 365 domains, are migrating to the *.cloud.microsoft domain. Therefore, Microsoft recommend performing the following steps as soon as possible to ensure your app continues to render on supported Microsoft 365 web client hosts:

    User's image

    It also stated that this migration is still in process, so it might not be fully updated yet.

    If the issue persists after you update your app, my recommendation is to reach out to Microsoft support team via https://admin.microsoft.com/#/homepage.

    User's image

    I hope this information helps.

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

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  1. Q&A Assist
    2026-05-04T08:27:56.5033333+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    Outlook and other Microsoft 365 web hosts are in the process of migrating to the *.cloud.microsoft domain. For iframe-hosted experiences (such as Teams tabs), the Content-Security-Policy frame-ancestors directive must explicitly allow the new hosts; otherwise, the browser blocks the content with errors like (blocked:origin).

    For Teams and Microsoft 365 apps, the documented frame-ancestors configuration is:

    • All hosts (new): *.cloud.microsoft
    • Teams: teams.microsoft.com, *.teams.microsoft.com
    • Microsoft 365 app: *.microsoft365.com, *.office.com
    • Outlook: outlook.office.com, outlook.office365.com, outlook-sdf.office.com, outlook-sdf.office365.com

    To restore rendering of Outlook content in Teams tabs:

    1. Update the CSP frame-ancestors directive on the Outlook-hosted pages (or the reverse proxy/front-end that serves them) so that it includes at least:
      • teams.microsoft.com
      • *.teams.microsoft.com
      • *.cloud.microsoft
    2. Do not remove the existing allowed origins; instead, append the new ones. This preserves backward compatibility while the migration to *.cloud.microsoft completes.
    3. Ensure the Teams app itself also follows the tab prerequisites:
      • Pages are served over HTTPS.
      • X-Frame-Options and CSP frame-ancestors allow Teams and other host applications, including *.cloud.microsoft.

    Administrators who configure CSP centrally (for example, in Power Platform or Dynamics 365 scenarios) should similarly add:

    • https://teams.microsoft.com/
    • https://teams.cloud.microsoft/

    to the frame-ancestors list where applicable.

    Once these hosts are added to frame-ancestors, the browser should no longer block the Outlook pages when rendered inside Teams, and the tabs should start working again.

    References:

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