A Microsoft 365 outage disrupted Outlook email and other services for thousands of users on Thursday, as the company said it was investigating problems reaching Exchange Online mailboxes through multiple connection methods in the Americas.
The first notice came from the company’s Microsoft 365 Status account on X shortly before 1 p.m. ET. “We’re investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas,” the post said, pointing administrators to the Microsoft 365 admin center under incident EX1550543.
The admin-center notice spelled out what was failing. Users could not connect to their Exchange Online mailboxes, it said, through Outlook on the web, the Messaging API (MAPI), Exchange ActiveSync (EAS) or the REST API.
Reports piled up fast. Downdetector logged a spike in Microsoft 365 complaints just after noon ET — 22,323 by 12:55 p.m. — and just shy of 83,000 Outlook reports before 1 p.m., according to USA TODAY’s live coverage. Around the same time, about 2,000 users reported trouble with Teams and 4,400 with Copilot.
The problem did not stay in the Americas. “While we’re working to mitigate impact, we’ve confirmed the issue may affect Microsoft 365 service connectivity for users in any region,” Microsoft posted at 1:07 p.m. Reports kept climbing, passing 47,000 for Microsoft 365 and nearing 130,000 for Outlook at about 1:20 p.m., Downdetector figures cited by USA TODAY showed.
What Microsoft found in its systems
In its admin-center updates, Microsoft said it had found connectivity errors on part of the Exchange Online infrastructure that receives and processes users’ access requests, and that engineers had gathered networking logs to hunt for the source of the errors.
By 1:43 p.m., the company said a portion of its infrastructure was carrying elevated load across multiple regions, which was likely contributing to the connectivity errors, and it opened a second incident, MO1550821, covering Microsoft 365 connectivity more broadly. Its list of affected services grew to include Teams, SharePoint Online, Microsoft Copilot and Microsoft Defender XDR alongside Exchange Online.
Traffic shifted while servers restart
Microsoft said it had begun redistributing connection traffic across its worldwide infrastructure to balance the load. In a 2:15 p.m. update, it said it had paused all deployments, was moving more traffic off the affected infrastructure and was restarting affected servers to bring them back into service. “We’re aggressively pursuing all pathways to reduce impact,” the update said.
Thursday’s email failure followed a separate Teams problem earlier in the day. Microsoft posted at 10:40 a.m. that it was investigating issues with Teams functionality in North America, tracked as TM1550488, and said in the same thread that those issues were resolved around noon, according to USA TODAY.
Microsoft had given no cause for the outage and no time for a full restoration by mid-afternoon. Its admin-center notice set 3 p.m. ET for the next update.
Update: Recovery progressing in Asia Pacific
In a Friday morning update, Microsoft said recovery actions were completed across portions of the affected infrastructure in the Asia Pacific region and that traffic was being gradually restored, with mailbox access and delayed email processing improving. The company said service health remained variable, that restored capacity had not yet returned to baseline, and it gave no time for a full restoration; overnight, it said servers returned to service could become unresponsive again once they received traffic.
Also Read: Microsoft 365 Outage Hits Outlook Email for Thousands