Microsoft 365 Outage Stretches Into Friday as Company Struggles to Restore Services
A sweeping disruption affecting Microsoft's email, cloud, and AI platforms persisted through Friday morning, with experts comparing the incident to some of the largest technology failures on record.
Microsoft 365 services across the globe remained offline Friday morning as the company continued recovery efforts from an outage that began midday Thursday. The disruption affected email, cloud storage, and artificial intelligence tools used by hundreds of millions of subscribers. Microsoft moved to safeguard customer data by extending email timeout windows to 48 hours while working to restore normal operations.
The scale of the incident drew comparisons to previous major technology failures. Ciaran Martin, former director of the UK's National Cyber Security Centre, told NBC News that the Microsoft disruption ranked among "one of the biggest outages of all time," and possibly "worse" than recent major incidents at Amazon Web Services and CrowdStrike.
The outage rippled across sectors and borders. Hospitals, police departments, schools, and government agencies worldwide reported significant disruptions. Japan's government IT infrastructure was affected, according to deputy chief cabinet secretary Masanao Ozaki. Medical professionals found themselves unable to communicate medication changes or follow-up instructions to patients. Financial institutions blocked customer transfers when verification codes failed to arrive. The Philippine Supreme Court saw legal proceedings delayed. A Colorado sheriff's office reported difficulty processing bond releases for detained individuals.
Microsoft estimated in January that more than 450 million paid commercial subscriptions existed for Microsoft 365, though the company has not disclosed how many users experienced the outage.
Failed health checks blamed for cascade of failures
Microsoft stated on its status page that "we have no evidence of malicious activity associated with this incident" and pledged to publish a full post-incident report detailing root causes and remediation steps once the situation stabilized.
The company's communications revealed that engineers were caught off guard and struggled to find reliable fixes. Microsoft initially identified the problem as "a portion of infrastructure" experiencing "elevated load across multiple regions," but clarified this was not due to traffic surges. Instead, "a problem that's causing servers to fail automated health checks and become unavailable" was responsible.
After determining that failed health checks were the culprit, Microsoft attempted to prevent further server failures while testing alternative health check procedures. Four hours into the incident, the company acknowledged limited progress.
We're opening all available pathways to restore service, as our actions taken thus far have not provided the anticipated relief. We found a core process on affected servers is becoming overwhelmed, causing capacity loss. To validate a potential recovery, we're isolating a portion of infrastructure, restarting affected components, and reintroducing traffic to confirm the services remain stable before applying the change more broadly.
Microsoft, via X
Recovery efforts encountered additional obstacles when restarted servers "become unresponsive again once they receive traffic," forcing engineers to address fresh problems. Recognizing that a swift resolution was unlikely, Microsoft extended email timeout to 48 hours as a protective measure.
Gradual recovery with lingering problems
By Friday morning, Microsoft reported "broader improvements in North America, sustained improvements across much of Europe, and encouraging recovery signals in Asia Pacific." The company cautioned that "some users may still experience intermittent access issues or delayed email delivery as mitigation continues across remaining affected infrastructure."
DownDetector, which aggregates user-reported service disruptions, showed that outages peaked Thursday afternoon and declined substantially by Friday morning.
User reports highlighted inconsistent recovery patterns. Outlook users noted that outgoing messages transmitted normally while incoming messages arrived sporadically. Copilot users expressed frustration that access restoration lagged behind other services. One Microsoft 365 subscriber questioned the broader impact, asking, "How many offices had people with practically nothing to do? How much has this cost?"