MC1120871 – (Updated) Important Update: Teams Meeting Join URL Validation

Product:

Exchange, Outlook, Teams, Windows

Platform:

Online, US Instances, Web, World tenant

Status:

Change type:

Admin impact, Feature update, Updated message, User impact

Links:

Details:

Summary:
Microsoft Teams will validate meeting join URLs starting September 30, 2025, to prevent altered or rewritten links from blocking access, affecting users of the old Teams calendar app. The new calendar app redirects safely without blocking. No admin action is needed for Safe Links users; third-party URL rewriting must exclude Teams links.

Details:
Updated September 11, 2025: We have updated the timeline. Thank you for your patience.
What and Who
To enhance the security and integrity of Microsoft Teams meetings, we are introducing a new feature that validates Teams meeting join URLs. This update helps ensure that meeting links are not altered or rewritten by security products in ways that could render them unusable or flagged as malicious. This is applicable only when user Joins a meeting from Teams old calendar.
Rollout Schedule
Worldwide: September 30, 2025
GCC, GCC High, DoD: November 30, 2025
Impact on Your Organization

Who is affected:
Organizations that use security solutions to inspect or rewrite URLs, as well as users who join Microsoft Teams meetings through the Teams platform, will be affected by this update.
What will happen:
Users using New Calendar App:

For new calendar app in Teams, Meeting joins will not be blocked instead users will be redirected to a outlook safelinks provider and again redirected to the destination rewritten Join url
This feature is enabled by default and does not require admin configuration.
For more information on New calendar in app in Teams follow this link: https://support.microsoft.com/en-us/office/get-started-with-the-new-calendar-in-microsoft-teams-98f3b637-5da2-43e2-91b3-f312ab3e4dc5
Old Teams Calendar App:
Microsoft Teams will validate join URLs to ensure they have not been modified.
If a join URL is rewritten or altered by a security product, it may be marked as malicious.
Users will be prevented from joining meetings if URLs are not in their original format.
This feature is enabled by default and does not require admin configuration.
Microsoft's advanced email security platform, including Safe Links (URL inspection/rewriting), will not be impacted by this update.
Safe Links Behavior:
Does not rewrite the URLs behind the "Join Teams meeting" or "Join" buttons.
Only rewrites URLs within the meeting invitation body.
Any temporary rewriting (if applied) is removed by Exchange Online upon send/receive.
Outlook Add-in Behavior
If meeting links are rewritten via Outlook add-ins during meeting creation, there is no impact.
Potential impact:
This change may affect third-party security services that rewrite both the body URLs and the "Join" button URLs.
Action required:
No action is needed for customers using Safe Links. There is no requirement to add Teams meeting URLs to the Safe Links "allowed list."
For the customer using 3P solutions, they must ensure Teams join links are excluded from rewriting.
Compliance Considerations: No compliance considerations identified, review as appropriate for your organization.
Workaround: Switch to New calendar to unblock users from joining the Meeting.
Platforms affected
Only Microsoft Teams affected, other platforms like outlook web and win32, outlook mac remain unaffected.

Change Category:
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Scope:
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Release Phase:

Created:
2025-07-24

updated:
2025-09-12

Task Type

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Docu to Check

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MS Preperations

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MS Urgency

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MS workload name

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summary for non-techies**

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Direct effects for Operations**

Meeting Access Issues
Users joining meetings through the old Teams calendar app may be blocked from accessing meetings if URLs are altered by security products, leading to disruptions in communication and collaboration.
   - roles: End Users, IT Support
   - references: https://support.microsoft.com/en-us/office/get-started-with-the-new-calendar-in-microsoft-teams-98f3b637-5da2-43e2-91b3-f312ab3e4dc5

Increased Support Tickets
The change may lead to an increase in support tickets as users encounter issues with joining meetings, straining IT support resources and impacting response times.
   - roles: IT Support, Help Desk Staff
   - references: https://support.microsoft.com/en-us/office/get-started-with-the-new-calendar-in-microsoft-teams-98f3b637-5da2-43e2-91b3-f312ab3e4dc5

User Frustration
Users may experience frustration and decreased productivity due to inability to join meetings, leading to potential dissatisfaction with IT services.
   - roles: End Users, Team Leaders
   - references: https://support.microsoft.com/en-us/office/get-started-with-the-new-calendar-in-microsoft-teams-98f3b637-5da2-43e2-91b3-f312ab3e4dc5

Dependency on Third-Party Solutions
Organizations relying on third-party security solutions may face challenges if those solutions do not exclude Teams URLs from rewriting, potentially leading to security risks or access issues.
   - roles: Security Administrators, Compliance Officers
   - references: https://support.microsoft.com/en-us/office/get-started-with-the-new-calendar-in-microsoft-teams-98f3b637-5da2-43e2-91b3-f312ab3e4dc5

Training and Awareness Needs
There may be a need for additional training and awareness programs for users to understand the changes and how to adapt to the new calendar app, impacting time and resources.
   - roles: Training Coordinators, End Users
   - references: https://support.microsoft.com/en-us/office/get-started-with-the-new-calendar-in-microsoft-teams-98f3b637-5da2-43e2-91b3-f312ab3e4dc5

Configutation Options**

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Opportunities**

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Potentional Risks**

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IT Security**

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explanation for non-techies**

Microsoft Teams is introducing a change to enhance the security of meeting links. Imagine you’re sending out invitations to a party. You write the address on each invitation, but some guests use a special service to double-check the address before they head out. Sometimes, this service changes the address slightly, which could lead to guests ending up at the wrong place or being unable to attend the party. To prevent this, you decide to verify that the address on each invitation hasn’t been altered, ensuring everyone arrives at the right location.

Starting September 30, 2025, Teams will start verifying the links used to join meetings to make sure they haven’t been changed by security tools. This is particularly important for users who are still using the older version of the Teams calendar app. If a link has been altered, it might be flagged as unsafe, preventing users from joining the meeting. However, if you’re using the new calendar app, there’s a safety net that redirects you correctly, so you don’t have to worry about these changes.

For organizations using security tools that inspect or rewrite URLs, it’s important to ensure that Teams meeting links are not altered. Think of it like telling your security service not to tamper with the party invitations’ addresses. This way, everyone can still get to the meeting without any issues.

For those using Microsoft’s Safe Links, which is like a trusted mail service that checks and delivers your invitations without altering them, there’s no need to take any action. However, if you’re using other security services, you’ll need to make sure they leave the Teams links unchanged.

This update doesn’t require any configuration changes from administrators, but it’s a good idea to check with your IT team to ensure everything is set up correctly. If you’re still using the old calendar app and encounter issues, switching to the new calendar app could resolve them, similar to using a new and improved invitation system that automatically guides guests to the right place.