A global outage of Microsoft 365 services stretched into a second day on Friday, leaving businesses, public agencies and other users across dozens of countries without reliable access to Outlook email, Teams calendars and related tools. Microsoft said early repair efforts had not delivered a sustained recovery and gave no estimate for when services would be fully restored.
The disruption began on Thursday afternoon, European time, in Exchange Online, the email service behind Outlook for business customers. Outage tracker Downdetector recorded reports from 74 countries and territories within about an hour, with Outlook complaints peaking at roughly 130,000, according to ITdaily and CIO&Leader.
The incident underlines how heavily companies now depend on a small number of cloud platforms for everyday communication. As of Friday morning European time, the root cause had not been confirmed, and Microsoft said restored servers were failing again once normal traffic returned.
Key Takeaways
- Outlook, Teams scheduling, Copilot and other Microsoft 365 services were disrupted worldwide from Thursday into Friday.
- Downdetector logged reports from 74 countries and territories, with Outlook complaints peaking at about 130,000.
- Microsoft said there was no indication of a cyberattack and was rolling back a recent network configuration change.
- The company had not given a time for full recovery as of Friday morning European time.
Services Hit Across Microsoft 365
The outage primarily affected mailbox access through Outlook on the web, desktop and mobile apps, with some messages arriving late. Teams calendars and meeting scheduling were also disrupted, although core chat and online meetings were reported to be largely working.
Copilot, SharePoint Online and parts of Microsoft’s Defender security tools were also affected, according to CIO&Leader and ITdaily. Artificial intelligence developers OpenAI and Anthropic both reported problems with their Microsoft 365 connectors, which depend on the same underlying services.
Microsoft tracked the incident under the identifiers EX1550543 for Exchange Online and MO1550821 for the wider Microsoft 365 suite. Both remained open on Friday morning without an estimated time for full recovery.
Repair Attempts Fail to Hold
Microsoft said the problems began when a number of servers became unexpectedly unavailable after failing automated health checks, placing heavy strain on the remaining capacity. The company said the issue reflected a loss of capacity rather than a surge in user traffic.
Overnight, engineers found that a core process responsible for setting up secure connections on the affected servers was being overwhelmed. Microsoft began reversing a recent network configuration change that coincided with the start of the disruption, but has not confirmed whether it caused the outage.
The company paused deployments, redistributed traffic, restarted servers and applied temporary traffic limits in some locations. In updates early on Friday, Microsoft acknowledged that these steps were not taking effect as expected, as restarted servers became unresponsive once traffic was restored. Charles Lamanna, Microsoft’s executive vice-president for Copilot, Agents and Platform, said there was “no indication this is the result of malicious or cyber activity.”
Disruption Spreads to Business and Public Services
The outage affected organisations across several regions as each began its working day. US electric vehicle maker Workhorse Group postponed its third-quarter results to 16 November, according to CIO&Leader and The Next Web, while public services in Australia asked customers to adjust plans as email systems failed.
The incident revives questions about concentration risk in cloud computing, a concern that analysts have raised for several years as Big Tech cloud services face growing resilience tests. It also follows a roughly ten-hour Microsoft 365 outage affecting North American users in January, and comes a year after a separate global cloud service disruption that affected essential digital services.
For businesses, the immediate costs include lost productivity, delayed communications with customers and the need to switch to backup channels. Regulators in several jurisdictions have increasingly pressed banks and other critical firms to plan for the failure of major technology providers, and the scale of this incident is likely to feature in those discussions.
Investor Focus on Reliability
Microsoft has become one of the main beneficiaries of corporate spending on cloud and artificial intelligence services, and its shares have been closely watched as Big Tech stocks swing on shifting market sentiment. The longer-term financial effect of the outage is not yet clear, but it may increase customer scrutiny of service commitments and compensation terms.
Enterprise clients typically receive service credits when availability falls below contractual levels, and some large customers may seek further assurances about resilience and recovery procedures. Microsoft has not disclosed any financial impact from the disruption.
Attention will now turn to whether Microsoft’s configuration rollback and capacity changes restore stable service over the weekend, and to the post-incident review the company typically publishes after major outages. That report is expected to clarify the root cause and outline measures to prevent a recurrence, which customers, investors and business leaders will examine closely.
