A widespread outage disrupted Microsoft's Outlook, Teams and other 365 services on Thursday, with nearly 130,000 users reporting problems accessing Outlook on Downdetector just after 1 p.m. ET, as the company investigated disruptions.
Many users said they couldn’t send and receive emails or had trouble loading their inboxes, while thousands reported issues with Teams, Copilot and wider Microsoft 365 services, according to outage reports and company updates.
Microsoft said it was aware of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas. The company said a portion of its infrastructure was experiencing elevated load, which it said was likely contributing to connectivity errors.
Microsoft determined that a number of servers had been unexpectedly unavailable due to a problem causing them to fail during automated health checks. The company later said it was testing a fix and rolling out an alternative method for these checks to bring impacted servers back online. “We’re aggressively pursuing all pathways to reduce impact,” the account wrote.
Earlier in the day, Microsoft said it had successfully restored Teams-related problems in North America, though some users continued to report connectivity issues. The exact cause of the server failure was not immediately clear.
Analysis
Why This Matters
- Disruption to widely-used enterprise tools affects productivity for millions of workers and organisations reliant on Microsoft 365 for email, collaboration, and AI features.
- The incident highlights the fragility of cloud infrastructure when automated health-check processes themselves trigger failures.
- The scale of the outage, nearly 130,000 reports, shows how even partial cloud service failures can cascade into broad user impact.
Background
Microsoft 365, including Outlook, Teams, and Copilot, is among the most widely used workplace software suites globally, with hundreds of millions of paid users. Outages of this scale are relatively rare; the company previously suffered a major Azure and 365 outage in July 2024 related to a DDoS attack and internal mitigation errors.
Key Perspectives
Microsoft: says the outage was caused by servers failing during automated health checks, leading to elevated load and connectivity errors, and that a fix is being tested to restore service via alternative check methods.
What to Watch
- Whether Microsoft's fix successfully restores all impacted servers and normal service levels.
- Any post-incident report identifying the root cause of the automated health-check failure.
- Potential regulatory or customer impact from the disruption.
Checked
11 claims in this story checked against 1 source: 11 supported.
Show each claim
- SupportedA widespread outage hit Outlook, Teams and other Microsoft 365 services on Thursday.OPB: “A widespread outage hit Microsoft platforms including Outlook on Thursday”
- SupportedNearly 130,000 Downdetector users reported Outlook problems just after 1 p.m. ET.OPB: “Nearly 130,000 users on outage tracker Downdetector reported problems accessing Outlook just after 1 p.m. ET.”
- SupportedMany users reported trouble sending or receiving email or loading their inboxes, and thousands reported issues with Teams, Copilot and Microsoft 365 services.OPB: “many said they couldn’t send and receive emails or had trouble loading their inboxes altogether. Thousands also reported issues with Microsoft’s workplace messaging app Teams, as well as its AI assistant Copilot and wider Microsoft 365 services.”
- SupportedMicrosoft said it was investigating disruptions, notably involving email and Teams.OPB: “Microsoft said it was investigating disruptions, notably related to its email and Teams applications.”
- SupportedMicrosoft said users were having trouble accessing Exchange Online mailboxes through multiple connection methods in the Americas.OPB: “Microsoft said it was aware of users “experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas.””
- SupportedMicrosoft said elevated load on part of its infrastructure was likely contributing to connectivity errors.OPB: “a portion of its infrastructure was “experiencing elevated load” — which it said was “likely contributing to the connectivity errors.””
- SupportedMicrosoft determined that some servers were unexpectedly unavailable because a problem caused them to fail during automated health checks.OPB: “The company determined a number of servers were “unexpectedly unavailable” due to a problem that caused them to fail during “automated health checks.””
- SupportedMicrosoft said it was testing a fix and rolling out an alternative method for the checks to bring affected servers back online.OPB: “Microsoft later said it was testing a fix and rolling out an alternative method for these checks to bring impacted servers back online.”
- SupportedThe Microsoft 365 Status account wrote, “We’re aggressively pursuing all pathways to reduce impact.”OPB: ““We’re aggressively pursuing all pathways to reduce impact,” the Microsoft 365 Status account wrote on X.”
- SupportedMicrosoft said it had restored Teams-related problems in North America, though some users continued to report connectivity issues.OPB: “Earlier in the day, the company said it had “successfully restored” problems related to Microsoft Teams in North America, although some users continued to report connectivity issues.”
- SupportedIt was not immediately clear what caused the server failure.OPB: “It was not immediately clear what exactly caused that failure.”
