Microsoft Outage Traced to Failed Server Health Checks
Microsoft said its global service outage stemmed from servers failing automated health checks, not from a surge in traffic. Recovery is progressing, but some users still face Outlook and Copilot problems.
US technology company Microsoft has explained the cause of a global service outage that hit its Outlook email service and its Copilot AI assistant. According to the company, part of its infrastructure was under elevated load across several regions, but the cause was not increased traffic. Instead, servers were failing automated health checks and becoming unavailable.
Once the cause was identified, Microsoft took steps to prevent further server outages while testing alternative health check methods. About four hours later, however, the company admitted that its actions had not brought the expected relief. It found that a core process on affected servers was becoming overwhelmed, causing a loss of capacity.
Recovery has not been straightforward
Microsoft is isolating part of its infrastructure, restarting affected components and reintroducing traffic to confirm stability before applying the fix more widely. Some servers brought back online, however, became unresponsive again once they received traffic. With no quick fix available, the company extended the email timeout to 48 hours.
The latest Microsoft updates point to broader improvements in North America, sustained improvements across much of Europe and encouraging recovery signals in Asia Pacific. The company warned that some users may still face intermittent access problems or delayed email delivery.
DownDetector, a website that tracks user reports of service problems, showed connectivity losses peaking on Thursday afternoon and falling substantially by Friday morning. Users complained that outgoing Outlook messages appeared to send normally while incoming ones arrived inconsistently, and some Copilot users were upset that access was not restored as quickly as Outlook. One Microsoft 365 user asked how many office workers had little to do and what the outage had cost.
