Microsoft service health
Microsoft reports sustained recovery across the previously affected environments. It is continuing extended monitoring and tracking the email backlog before declaring the incidents resolved, while the majority of dependent Microsoft 365 impact scenarios are believed to be addressed.
Incident timeline
The milestones below condense Microsoft's incident updates for EX1550543 and MO1550821. All times are GMT/UTC.
Microsoft reported sustained recovery across the previously affected environments. Because of the severity of the incident, it is monitoring for an extended period to confirm that no further mitigation is required and that the email backlog processes successfully before declaring the incidents resolved. Microsoft believes the majority of dependent Microsoft 365 impact scenarios have been addressed. Its next update is due by 02:30 GMT on 14 November.
Microsoft reported that infrastructure is stabilizing and sign-in and service access are improving. Queued messages are still being drained and traffic rebalanced, so mail delivery and processing remain behind normal levels. Microsoft has not provided an ETA for full recovery and cautioned that access may recover before mail flow fully normalizes. Its next update is due by 00:00 GMT on 14 November.
Microsoft reported broad recovery and stability across its services. It said an issue during an earlier network capacity upgrade surfaced after a recent network change; the underlying issue has been addressed, while restoration continues for the remaining customers and regions. Microsoft confirmed the incident was technical and not related to cyber activity or AI/agents.
Microsoft said work remained focused on residual impact and reliable service restoration. Recovery continued to be assessed across connection methods while service health was closely monitored to confirm sustained stability. The incident remained active, with no evidence of malicious activity.
Microsoft reported sustained improvements in service availability across affected Microsoft 365 services. Work increasingly focused on resolving the remaining issues and restoring consistent service for all affected users, while recovery was validated across connection methods. Some users could still experience intermittent connectivity issues or delayed email delivery.
Microsoft reported continuing improvement in service availability, with email queues significantly reduced and approaching normal levels. Additional mitigation measures were implemented while the remaining affected infrastructure was restored and residual service issues investigated. Some users could still experience intermittent access issues or delayed email.
Microsoft reported broader improvements in North America, sustained improvements across much of Europe and encouraging recovery signals in Asia Pacific. Some users could still experience intermittent access issues or delayed email while Microsoft stabilized recovered infrastructure, completed mitigation in the remaining affected areas and reduced email queues and backlogs.
Microsoft's broader MO1550821 update confirmed encouraging recovery in Europe, improving conditions in North America and comparatively stable service in Japan. Some users could still experience intermittent issues while recovery continued and email queues and backlogs were reduced.
Microsoft reported encouraging recovery progress in Europe, with service availability and email delivery improving across more affected infrastructure. North America was also improving and Japan remained comparatively stable, though some users could still experience intermittent issues while email queues and backlogs were reduced.
Recovery actions completed across parts of the Asia-Pacific infrastructure and traffic was gradually restored. Mailbox access and delayed-email processing improved, but intermittent issues remained while recovery expanded to other regions.
Recovery proceeded in controlled phases. Microsoft extended the email timeout window to 48 hours to protect delayed messages and said it had no evidence of malicious activity.
Microsoft expanded the patch to infrastructure supporting regions entering peak business hours and continued monitoring server stability and capacity.
An upstream authentication and routing configuration patch produced positive server-stability results on part of the infrastructure and was prepared for wider expansion.
Microsoft confirmed the serviceability change was not taking as expected and moved to alternative workstreams to increase capacity amid sustained traffic-management imbalances.
Microsoft reported that a secure-connection process was becoming overwhelmed. A configuration fix was prepared while a recent network change correlated with the start of impact was rolled back.
Returned servers became unresponsive again when traffic resumed. Microsoft restricted traffic types in selected locations and rebuilt a subset using an earlier software configuration.
Some servers remained stable and traffic shifted to alternate paths. Protective traffic-management measures were introduced while users began seeing limited recovery in some regions.
Microsoft found a core process was becoming overwhelmed and stopping servers from responding. Infrastructure was isolated, restarted and brought back under gradually reintroduced traffic.
An alternative health-check method returned a subset of servers to service. Microsoft began expanding it and prepared automated detection and restart of unresponsive servers.
Microsoft said elevated load was caused by many servers becoming unexpectedly unavailable, shifting demand onto the remaining infrastructure. Deployments and configuration changes were paused.
MO1550821 expanded the scope to multiple Microsoft 365 services and regions as elevated load and connectivity errors spread beyond Exchange Online.
Microsoft opened EX1550543 for mailbox connection failures across Outlook on the web, desktop and mobile protocols, with possible delayed email delivery.
Timeline compiled from Microsoft Service Health incidents EX1550543 and MO1550821, the Microsoft public status page, the EX1550543 incident mirror, the MO1550821 incident mirror, and Associated Press reporting. Microsoft identified the technical network issue behind the incident at 17:57 GMT. At 22:00 GMT it reported sustained recovery, said the majority of dependent impact scenarios were addressed, and continued extended monitoring of the email backlog before considering the incidents resolved. A full post-incident report will follow after its review is complete.
