Is Microsoft Outlook Down? Microsoft 365 and Copilot Hit by Widespread Outage as Users Face Disruption

Microsoft confirmed a widespread Microsoft 365 disruption on Thursday, 12 November, as users reported problems accessing Outlook, Teams and Copilot. The email disruption centred on Exchange Online, Microsoft's hosted email service for business and organisational accounts.

The company warned that connectivity problems could affect customers in any region and began work to restore unavailable servers.

Microsoft said those servers were placing pressure on the infrastructure still operating, rather than an increase in traffic driving the disruption. Its later updates described failed automated health checks and a targeted workaround, but did not establish the underlying cause or confirm full service restoration.

Outlook Disruption Reaches Other Microsoft Services

The company's advisory identified Exchange Online, Microsoft Teams, SharePoint Online, Microsoft 365 Copilot and Microsoft Defender XDR among services customers might be unable to access. That warning covered potential connectivity problems, rather than confirming that every function or customer within each service was affected.

Complaints also increased across Outlook, Microsoft 365, Teams, Copilot, Azure, OneDrive and the Microsoft Store on Downdetector, which tracks user-submitted outage reports. Those submissions indicated difficulties across several platforms but did not provide a verified count of affected customers.

Microsoft Identifies Pressure on Remaining Servers

Microsoft initially identified elevated infrastructure load across multiple regions as a likely contributor to the connectivity problems. It subsequently clarified that the strain resulted from servers unexpectedly becoming unavailable, shifting their load onto the remaining infrastructure.

The company's statements were reproduced in BleepingComputer's outage report and Tom's Guide's live coverage. They distinguished the immediate capacity problem from the unresolved question of why the affected servers had become unavailable.

Microsoft 365 Incident Followed Mailbox Investigation

The wider incident was listed in Microsoft's service advisory under reference MO1550821, with a start time of 1.26pm ET, or 6.26pm GMT. The company had initially investigated Exchange Online mailbox connectivity issues in the Americas before identifying the broader disruption.

Microsoft later warned that service connectivity could be affected in any region, expanding the potential scope beyond the initial mailbox investigation. That geographical warning did not establish that every region experienced disruption or that all customers lost access at the same time.

Recovery Work Includes Traffic Redistribution

Microsoft redistributed connection traffic across its worldwide infrastructure and moved additional traffic away from affected systems to reduce pressure. It also began restarting affected servers to return capacity to service while investigating the reason for their unavailability.

Deployments and configuration changes were paused as a precaution while the company reviewed recent changes for a possible connection to the incident. In subsequent updates, Microsoft said it had not identified any recent change that correlated with the start of the disruption.

Microsoft Tests Server Health-Check Workaround

The investigation later focused on automated health checks that servers were failing, causing them to become unavailable. Microsoft said those failures might originate from a specific component responsible for processing the checks, rather than identifying a definitive underlying cause.

The company described deploying a targeted change to bypass that component on a subset of servers to test whether availability improved. It was also investigating elevated processor usage while handling requests and taking steps to prevent additional servers from being removed from service.

Earlier Teams Incident Was Reported Resolved

A separate Teams incident, TM1550488, affected users in North and South America between 9.45am and 10.53am ET earlier that day. It caused delays or failures when sending messages, errors updating conversations and difficulties retrieving chats.

Microsoft attributed that earlier disruption to resource contention within its infrastructure and reported it fully resolved. The company had not established whether it was connected to the later Microsoft 365 incident, whose recovery remained incomplete in the updates reviewed.