Microsoft 365 outage disrupts Outlook, Teams and Copilot worldwide; full recovery not yet confirmed
A global Microsoft 365 outage that began on Thursday at 11:17 ET disrupted Exchange Online and Outlook, Teams features, SharePoint Online, Copilot and Defender XDR for users in any region. Microsoft says a large number of its servers became unexpectedly unavailable after failing automated health checks — not a traffic surge, and with no indication of a cyberattack. User reports for Outlook on Downdetector peaked at 138,058 around 13:00 ET. Microsoft began returning some servers to service on Thursday evening, but a change applied late on Thursday was 'not taking as expected', and full recovery had not been confirmed in the latest updates read.
Checking in progress
This story is still being checked. Claims below are published as claims — never dressed as facts — and each one moves only when the evidence earns it.
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4 of 4 claims checked so far · step 4 of 4: Human gate
Key points
- Started Thursday 11:17 ET (incidents EX1550543 / MO1550821); Outlook, Teams features, SharePoint, Copilot and Defender XDR disrupted in any region.
- Microsoft: servers failed automated health checks and became unavailable, overloading the rest — not a traffic surge, no indication of a cyberattack.
- Downdetector Outlook reports peaked at 138,058 around 13:00 ET — user reports, not an affected-customer count.
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- Partial recovery began Thursday evening; a later change was 'not taking as expected' and full recovery was not yet confirmed.
What happened
The failure spread because the services share one infrastructure: when servers dropped out after failing their health checks, the load shifted onto those still standing, and Exchange-dependent features in Teams and elsewhere failed with the mail system. By Friday the disruption had reached government users in Australia, where the spy agency and federal police were among those hit.
What we know / what we don't know yet
What we know
- That the outage began at 11:17 ET on Thursday, which services were affected, and Microsoft's own account of the mechanism, from its service-health record.
What we don't know yet
- Whether full recovery has been achieved — not confirmed in the latest Microsoft updates read.
- The root cause — Microsoft has published none, and a small number of configuration updates were still being investigated as possible contributors.
- How many customers or users were affected in total — Microsoft has published no figure.
Claim by claim
Show all claims (4)
Why this label: The start time, incident references and service scope are Microsoft's own service-health record as relayed by the three outlets; core Teams chat and meetings were reported largely functional, which is why the scope is stated feature by feature.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
Why this label: This is Microsoft's own explanation of the mechanism, verified as its statement; it is not a root cause, and none has been published.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
Why this label: Downdetector counts are user-submitted reports, not a count of affected customers — Microsoft has not published an affected-user total, and none is claimed here.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
Why this label: The recovery sequence is Microsoft's own update language as relayed by Reuters and USA Today; the story therefore stays in Checking state until Microsoft confirms full restoration.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
Why it matters
Outlook and Teams are the working day for much of the world's office staff, and this outage ran for hours across every region at once — with, so far, an explanation of the mechanism but no root cause, and no confirmed end. Until Microsoft confirms full recovery, every reopening of the working day in a new time zone tests the fix again.
Background
Show the background timeline (4)
Microsoft's Exchange Online incident EX1550543 begins; the wider advisory MO1550821 follows.
Downdetector reports for Outlook peak at 138,058.
Microsoft begins returning a portion of servers to service; limited, gradual recovery.
Microsoft says an applied change is 'not taking as expected'; by Friday morning the outage has hit Australian government agencies.
Update history
No silent edits. Every change is written here, with its time.
- Latest
Published in Checking state — the outage, its scope and Microsoft's explanation are confirmed; full recovery has not been confirmed in the latest updates read.