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Issue Description : Users’ Free/Busy information may be outdated.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