Migrate Free/Busy, MailTips, and Calendar Sharing before EWS deprecation

🚨 The Signal: Exchange Web Services (EWS) for cross-tenant Free/Busy, MailTips, and Calendar Sharing will be deprecated by October 2026. Organizations must migrate to Microsoft 365 Cross-Tenant Access Policy to maintain these collaboration features.

The Impact

Organizations using EWS for cross-tenant Free/Busy, MailTips, or Calendar Sharing are affected, risking loss of secure collaboration features if not migrated.

  • Security Teams: Risk of unmanaged information sharing if EWS is not replaced.
  • Admins: Must reconfigure cross-tenant sharing policies to maintain functionality.
  • External Collaborators: Potential disruption to Free/Busy and MailTip exchange.
  • Compliance Officers: Need to ensure continued secure data sharing practices.

The Action

  1. Identify existing Exchange Online Organization Relationships, Availability Address Spaces, or Sharing Policies using EWS.
  2. Plan migration to Microsoft 365 Cross-Tenant Access Policy for Free/Busy, MailTips, and Calendar Sharing.
  3. Configure new Cross-Tenant Access Policies in the Microsoft 365 admin center or via PowerShell.
  4. Test cross-tenant collaboration features with partner organizations post-migration.
  5. Deprecate old EWS-based configurations once new policies are confirmed operational.

Domain: Exchange · Impact: medium · Workload: Exchange Online