(Updated) Auto upgrade of shared calendars from legacy MAPI model to modern REST model

🚨 The Signal: Microsoft is upgrading shared calendars from legacy MAPI to modern REST, improving sync reliability and performance. This server-side change is automatic and aims to be seamless, with no user or admin action required.

The Impact

Users accessing shared calendars will experience improved reliability, with no direct security risk or action required.

• Shared calendar users: Improved performance and reliability.
• Delegates: Better calendar sync consistency.
• Admins: No action or configuration changes needed.
• Security teams: No direct security posture change.

Domain: Exchange · Impact: low · Workload: Exchange Online