URL Protect - Microsoft Teams Update Action Required - Jul 2025

Service Update

Availability	July 29th, 2025
Product(s)	Targeted Threat Protection, URL Protect
Who's affected	Targeted Threat Protection Administrators & Microsoft Teams End Users

Overview

Microsoft Teams will begin validating Teams meeting URLs to ensure they have not been altered on September 30th, 2025.

What's changing

• Per MC1120871 from Message center in the Microsoft 365 Admin Center, Microsoft Teams meeting join URLs will be validated by Microsoft to ensure they have not been rewritten or altered. If a link has been altered, users may be prevented from joining the meeting.

Recommended actions

As per Microsoft's recommendations for their upcoming change, you should make the following updates:

• Ensure that your security products do not rewrite Microsoft Teams meeting join URLs.
• Allowlist Microsoft Teams join URLs in your security software.
• Review your organization's URL rewriting or inspection policies, before the rollout date.
  • From a Mimecast perspective, this would include URL Protection, and we would suggest creating a Managed URL entry set, to permit and disable rewriting on the Microsoft Teams join URL relevant to your organization.
• Communicate this change to your helpdesk staff and teams.
• Add a managed URL entry in Mimecast under Email Security | URL Protection | Managed URLs | Add Managed URLs
  • Select Permitted URLs as the Override Type.
  • Ensure the Rewriting toggle is set to Disabled.
  • Select Domain as the Match Type.
  • Add the following Microsoft Teams URLs to the URLs box:

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

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  • Add a description or comment to the Comment box.
  • Select Save and Close.

See Also...

• Targeted Threat Protection - URL Protect - Managed URLs
• M365 Admin Center Announcement