Microsoft 365 Alert – Service Degradation – Exchange Online – Users’ Free/Busy information may be outdated – RESOLVED

19/07/2023 10:02:00 AM (GMT)

NHSmail Reference : INC37099312

Microsoft Reference : EX649488

Issue Status : RESOLVED

Issue Description : Users’ Free/Busy information may be outdated.

More info : Recent changes to users” free/busy status may be delayed or not accurately reflected. This may impact any user reviewing the free/busy status of any other user in any Exchange Online connection method.

Final Update : 26/07/2023 08:28:00 AMMicrosoft have completed applying the caching configuration change to all affected infrastructure and validated remediation via service telemetry.

Scope of impact : Users serviced by the affected infrastructure attempting to update their Free/Busy status are impacted.

Root cause : A recent feature update intended to improve the Free/Busy feature resulted in a large influx of Free/Busy Control Flow Messages (CFM) to be sent to the Exchange Online infrastructure, resulting in stale Free/Busy information.

Next steps : Microsoft are continuing their review of the free/busy update that resulted in impact to better understand the underlying cause of impact and prevent similar issues in the future.

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