On 12 November, Exchange Online mailbox access and several linked Microsoft 365 services broke down for users across multiple regions, starting at 16:17 UTC. Microsoft has filed 35 status updates across three related incidents and the problem is still open as of its last post. This one is on Microsoft's infrastructure, not yours.
Started
16:17 UTC
Duration
Ongoing
Source
IsDown
Next time
Microsoft 365 is degraded. Is your product working?
An incident on their side does not always mean an outage on yours, and the only way to know is to already be watching your own endpoints. Set that up in under a minute and you will be notified the next time your own site is affected. And there will be a next time.
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Affected components: Microsoft 365 suite, Dynamics 365 Apps, Exchange Online
What happened?
Microsoft opened its first incident at 16:17 UTC, reporting that users might be unable to connect to their mailboxes in Exchange Online through multiple connection methods, including Outlook on the web, MAPI, Exchange ActiveSync and REST-based API calls. By 18:19 UTC Microsoft said the affected infrastructure was under elevated load across multiple regions and that it was restarting and repairing servers while evaluating a reroute to alternate infrastructure. A second incident, opened at 17:00 UTC, covers Dynamics 365 Contact Center, where agents could not send or receive messages and voice calls, with Microsoft later restarting a transcript service after a failover produced intermittent failures viewing conversation transcripts. A third incident, opened at 18:26 UTC, widened the picture to multiple Microsoft 365 services at once, naming Exchange Online, Microsoft Teams, SharePoint Online, Microsoft Copilot 365 and Microsoft Defender XDR as potentially affected. Microsoft's longest update, filed at 00:45 UTC, lists a long run of features tied to Exchange Online dependency: Copilot Chat failing to load or respond, Defender for Office 365 Safe Links unable to verify URLs, Microsoft Graph mail and calendar API calls timing out, Planner reliability issues, and several Purview services affected, among others. By the 01:06 UTC update on the mailbox incident, Microsoft said a process on affected servers responsible for establishing secure connections was becoming overwhelmed and causing those servers to stop processing requests, and that it was both preparing a configuration fix and reverting a recent network configuration change that correlates with the start of impact. All three incidents remain marked ongoing, with the mailbox incident's most recent update promising a further report by 2:00 AM UTC on 13 November. No user reports were filed during this window. Microsoft's own postings are the only record here, and they describe cause, scope and mitigation changing several times over the day rather than settling on a single explanation.
Learning
Microsoft's own updates describe a server-side failure: a connection-handling process on Exchange Online infrastructure became overwhelmed and stopped processing requests, a fault that sits entirely inside Microsoft's data centres and would not show up in anything you can watch from your own side. If your product depends on Exchange Online, Dynamics 365 Contact Center or any of the dozen-plus services named in Microsoft's 00:45 UTC update, your own uptime checks on your application layer could stay green the whole time while mail, Copilot, Graph calls and Purview operations all fail upstream. That is the normal shape of a provider-side outage: your endpoints answer fine, but the service behind them does not. Over the last 90 days Microsoft has logged 63 incidents with a median duration of 7 hours 20 minutes, so an outage like this one running past the half-day mark is not unusual for this provider. UptimeRobot's own 30-day figures for Microsoft show 24 incidents with a median duration of 13h 22m, a longer figure than Microsoft's own median, which reflects outside monitoring catching effects users feel before and after a vendor marks things resolved. Your monitoring covers your half, UptimeRobot now watches the provider's half too, so next time you know which side broke without guessing.
