Nearly 130,000 users on outage tracker Downdetector reported problems accessing Outlook just after 1 p.m. ET. New reports have since fallen from that peak, but 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.
Microsoft said that it was investigating disruptions, notably related to its email and Teams applications.
In updates posted on social media, Redmond, Washington-based Microsoft said it was aware of users “experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas.”
Microsoft later explained that a portion of its infrastructure was “experiencing elevated load" — which it said was “likely contributing to the connectivity errors.” The company determined a number of servers were “unexpectedly unavailable” due to a problem that caused them to fail during automated checks.
Microsoft did not immediately provide more information around what might be causing that failure, but added that it was testing a fix.
“We're aggressively pursuing all pathways to reduce impact,” the Microsoft 365 Status account wrote on X.
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.