Is Microsoft Outlook Still Down? Microsoft Says Email Is Restored After Outage That Lasted More Than 24 Hours

Microsoft said early Saturday it had fully restored Outlook and its other Microsoft 365 services. The outage lasted more than a day and hit businesses, airlines, hospitals and government agencies around the world.

"We have completed our efforts to address the underlying issue of the incident and restored service to the remaining impacted customers and regions," the company said in a post on its Microsoft 365 Status account on X.

Microsoft told administrators that further updates would be posted under incident MO1550821 in the Microsoft 365 admin center.

By Saturday morning, outage-tracking websites showed Outlook running normally, with user reports back near typical levels. Users who still can't get in or are missing messages may be seeing leftover effects from the disruption. That includes delayed emails that piled up while the system was down.

What Happened

The trouble began around midday Eastern time on Thursday. Users across North America started reporting that they couldn't open their inboxes, send messages or sign in.

At 12:54 p.m. ET, Microsoft acknowledged the problem. "We're investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas," it said on X.

Downdetector reports rose quickly. More than 129,000 people in the United States had reported Outlook problems by shortly after 1 p.m. ET Thursday. Chicago, Seattle and New York were among the hardest-hit cities.

The problem soon spread beyond email. On its service health page, Microsoft warned that "users may be unable to connect to multiple Microsoft 365 services." Teams, the AI assistant Copilot and SharePoint Online were among the services affected. The company later said the issue could affect users in any region.

According to Digital Trends, which cited Downdetector, the tracker logged more than 7.4 million outage reports worldwide during the incident. The figure counts reports, not individual users. Downdetector said reports came from more than 70 countries and territories.

Outage Stretches Into Second Day

Microsoft's first fixes didn't hold. Engineers restarted affected servers, but some became unresponsive again once traffic returned, so the company had to try other ways to bring service back.

As Europe and Asia began their Friday workday, the outage was still widespread. Microsoft extended its email timeout window to 48 hours to reduce the chance that messages sent during the outage would be lost.

On Friday the company began reporting progress. It said it was "seeing encouraging recovery progress, with service availability and email delivery performance improving across a growing portion of affected Microsoft 365 infrastructure."

Inboxes gradually came back to life Friday. Some users received a trickle of delayed messages. Microsoft said it would keep watching the backlog of mail that built up during the disruption.

"Due to the severity of impact this incident caused, we're monitoring for an extended period to ensure no additional mitigative actions are required," the company said.

Cause Traced to Network Upgrade

Microsoft said the outage was not caused by a cyberattack. It said the incident "was introduced by an issue during an earlier network capacity upgrade that surfaced following a recent network change."

The company also described it as "a technical issue not related to cyber or AI."

Digital Trends reported that Microsoft first suspected unusually heavy traffic. Investigators then found that several backend servers had unexpectedly gone offline, leaving the remaining servers struggling with the load. Engineers eventually deployed a patch to an authentication and routing component, then slowly restored traffic and worked through the delayed email.

Microsoft has promised a fuller post-incident report.

Wide-Ranging Impact

The outage disrupted operations far beyond office inboxes. Microsoft says more than 430 million people use its Microsoft 365 apps.

The governments of Japan, Singapore and Australia said the disruption affected some of their operations. Courts, health care providers, banks and airlines also reported problems.

In Canada, hospitals said the outage affected some services, while stressing that patient care was not affected. Via Rail warned that passengers might not get email updates about their trips.

In Britain, the National Health Service relied on alternative systems, Reuters reported. Indian carriers Air India, IndiGo and Akasa Air reported problems with email support. In Taiwan, one financial firm fell back on fax machines to confirm trades.

Hong Kong businessman Danny Lau, who runs an aluminum company, said his firm's Outlook accounts couldn't receive updates from U.S. customers. He warned that a longer outage could "impact the production timeline."

Electric truck maker Workhorse Group moved its quarterly earnings release to Nov. 16 after the disruption.

The cost of the outage could top $7 billion, according to one estimate reported by CNN. Variety reported that affected customers can ask Microsoft for service credits for the interruption.

What Users Can Do Now

Microsoft says service is restored. Users who still have trouble can try the usual steps:

• Sign out and back in.
• Restart the Outlook app or browser.
• Check the Microsoft 365 service status page.

Business and enterprise customers can follow incident MO1550821 in the Microsoft 365 admin center for official updates.

Emails sent during the outage may arrive late as the backlog clears. Users expecting important messages may want to check with senders before resending.

Latest in a Series of Disruptions

This week's failure is one of the longest Microsoft cloud outages in recent years. Outlook and Microsoft 365 have had several disruptions over the past two years, including:

• a roughly 24-hour outage of Outlook and Teams in November 2024
• a weekend login failure in March 2025, which Microsoft blamed on a problematic code change
• a mailbox infrastructure problem in July 2025 that knocked Outlook offline for more than 11 hours

Each outage has drawn fresh questions about how dependent businesses and governments have become on a few cloud providers. Analysts have said multi-hour failures across core Microsoft 365 services usually point to significant problems in the company's underlying cloud infrastructure.

For now, Microsoft says the immediate crisis is over, and its full account of what went wrong is still to come.