A Microsoft 365 outage that began shortly before 1 p.m. ET on November 12 cut off Exchange Online mail, Teams, SharePoint, Copilot and Defender XDR for users in every region. Microsoft blames servers that became unavailable and says recovery is rolling out. What admins and users should do while it finishes.
If Outlook, Teams or SharePoint stopped working for you on Thursday afternoon, the problem is on Microsoft’s side. A Microsoft 365 outage that began shortly before 1 p.m. ET on November 12 cut off Exchange Online mailboxes and other services for business and consumer users, and Microsoft says it can affect users in any region. Don’t reset passwords or reinstall Office. Microsoft tracks the incident as EX1550543 and MO1550821 in the Microsoft 365 admin center.
What broke and who is affected
Microsoft’s first post on its Microsoft 365 Status account on X described problems reaching Exchange Online mailboxes “through multiple connection methods in the Americas.” Within the hour it widened that to service connectivity for users in any region, according to Global News and TechCrunch.
Microsoft’s service status page listed Exchange Online, Microsoft Teams, SharePoint Online, Microsoft 365 Copilot and Microsoft Defender XDR, according to Engadget. XDA Developers later added Planner, To Do and Purview from the same page. TechCrunch reports that consumer Outlook.com inboxes, OneDrive and Office for the web were hit too. A Microsoft spokesperson told CNBC the problems were primarily with Exchange Online.
The scale was large. Tom’s Guide’s live coverage saw Downdetector reports for Outlook peak above 131,000 in the early afternoon. For a while the Microsoft 365 admin center itself was unreachable, so Microsoft posted updates on X.
What Microsoft says caused it
Microsoft’s updates over the afternoon, as reported by CNBC, Global News and XDA:
- It first pointed to elevated load across multiple regions and began moving connection traffic onto its wider worldwide infrastructure.
- It then said traffic had not grown. A large number of servers had become unexpectedly unavailable, which pushed their work onto the remaining servers.
- Around 2 p.m. ET it paused deployments and configuration changes and began restarting the affected servers.
- Shortly before 3:30 p.m. ET it said the failed health checks may come from a specific component that processes server health, and that it had found no recent change matching the start of the outage. It later said it was investigating a small number of configuration updates as possible contributors.
- Around 4 p.m. ET it said an alternative health check method had returned a subset of servers to service, that it was applying the change more broadly, and that it was preparing an automated process to detect and restart unresponsive servers.
Microsoft has not named a root cause. Later in the afternoon, TechRadar reported OneDrive was still failing for its own staff and said a full fix before the end of the East Coast workday looked unlikely.
What to do
- Admins: watch the incident, not the help desk queue. Follow EX1550543 and MO1550821 in the admin center. If the admin center won’t load, use status.cloud.microsoft and the Microsoft 365 Status account on X.
- Don’t change working settings. Mail clients, passwords and DNS records are not the problem here. Restarting Outlook may help once your tenant’s servers come back, and nothing more is needed on your end.
- Move time-critical messages for the afternoon. If a deadline depends on email or a Teams call, use a phone call, a personal address or another meeting tool, and tell the other side why.
- Expect delayed mail. Sending mail servers normally retry for hours when a mailbox host doesn’t answer, so messages sent to you may arrive late. Check for late arrivals once service returns before asking anyone to resend.
- Write it down. If your company relies on Microsoft 365, note the hours you lost and keep the incident IDs. Your admin will need them for any service credit claim or vendor review.
A single point of failure for remote teams
This is our analysis. For a remote company on Microsoft 365, mail, chat, files and calls all sat behind the same failing servers on Thursday. A distributed team has no hallway to fall back on, so an afternoon-long gap in Exchange and Teams stops work in a way it doesn’t for an office.
It also lands in a rough week for Microsoft mail. Outlook.com has been bouncing legitimate messages over SPF checks since last week, and November’s Patch Tuesday fixed an exploited Outlook flaw. TechCrunch notes Microsoft’s last major Microsoft 365 outage, in September, lasted days and was blamed on an authentication configuration problem. If your team has no agreed backup channel for a day like this, pick one now: a group text thread or a second meeting tool costs nothing to set up before the next outage.