Microsoft 365 Outage Mostly Resolved After Two-Day Disruption

Microsoft reported Friday that its global service outage has been mostly resolved, with "broad recovery and stability" across Microsoft 365 services — roughly 24 hours after the disruption began Thursday and knocked Outlook, Teams, Copilot and SharePoint offline for users around the world.

The outage hit corporate communication and collaboration infrastructure at scale. For finance teams, that means email queues, document workflows and collaboration channels that ran through Microsoft's cloud were unreliable for a full business day. University students, staff and faculty were among those affected, according to the University of Illinois's Office of the Chief Information Officer, which published an update Friday.

What caused the outage?

Microsoft 365 Status posted Thursday that some servers became unavailable, straining the remaining infrastructure and triggering the outage. The root cause, the company said Friday on X, traced back to its own upgrade work.

"The incident was introduced by an issue during an earlier network capacity upgrade that surfaced following a recent network change," the Microsoft 365 Status post read. "We have addressed the underlying issue and continue to restore service to remaining customers and regions."

In plain words: a routine capacity upgrade went wrong, and the flaw only showed up after a later network change exposed it.

What should businesses do now?

The University of Illinois's Office of the CIO issued practical guidance that applies to any organization running on Microsoft 365:

• Check Outlook outboxes and drafts folders for emails that failed to send during the outage.
• Confirm delivery by reviewing the sent folder.
• Expect a backlog. Emails are processed before entering a queue, so the office predicts a buildup of undelivered messages that could delay sending and delivery times.
• Set a deadline for escalation. Anyone expecting an email that hasn't arrived by Monday should submit a support ticket to their IT service desk.

The office said it does not expect further updates over the weekend, signaling that residual recovery work will continue into the new week without additional official communications.

Why the backlog matters

The queue mechanics are the detail worth watching. Because Microsoft processes messages before queuing them for delivery, a day-long outage doesn't simply discard pending mail — it stacks it. Sending and delivery times could lag even as dashboards show services healthy, which is why the CIO office set Monday as the threshold for raising a ticket rather than expecting instant normalization.

For finance operations that depend on time-stamped correspondence — confirmations, approvals, vendor communications — that lag carries real risk of missed deadlines during the recovery window.

Microsoft says the underlying issue is fixed and restoration continues for remaining customers and regions.