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Microsoft Investigates Global Microsoft 365 Connectivity Outage
By Clara Ledger
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Microsoft is investigating a global outage affecting Microsoft 365 connectivity, the company said on Thursday, after users reported being unable to reach Exchange Online mailboxes through multiple connection methods.
The incident, tracked by Microsoft as EX1550543, began Thursday morning. Microsoft’s service health notice puts the start at 11:17 a.m. Eastern, according to Microsoft.
Microsoft later confirmed that the issue may affect Microsoft 365 connectivity in any region, according to Microsoft.
The affected services include Outlook, Teams, SharePoint Online, OneDrive, Copilot and Microsoft Defender XDR, according to Microsoft.
Downdetector reports for Outlook peaked at more than 130,000 around 1:27 p.m. Eastern, according to Reuters, which cited Downdetector data.
Microsoft said the elevated load is not driven by an increase in traffic, according to Microsoft. Instead, the company said a large number of servers were unexpectedly unavailable, straining the remaining infrastructure.
Microsoft has paused deployments, redistributed connection traffic across its worldwide infrastructure, and is restarting affected servers, according to Microsoft. Some servers were returned to service by mid-afternoon Eastern, according to Microsoft.
Microsoft has given no root cause and no restoration time, according to Microsoft, and has not linked the outage to a cyberattack.
That absence is itself an important part of the picture. Without a root cause, users and administrators cannot yet know whether the problem is a software fault, a configuration failure, a hardware issue or something else entirely. Microsoft has not said.
What is clear is that the disruption is not confined to a single product or a single way of connecting. Users have been unable to reach Exchange Online mailboxes through multiple connection methods, according to Microsoft, a detail that points to a problem in the underlying connectivity infrastructure rather than a single client or app.
For now, Microsoft’s public updates describe action rather than explanation: deployments paused, traffic redistributed, servers restarted. Some servers were returned to service by mid-afternoon Eastern, according to Microsoft, but the company has not said how many remain unavailable or when full service will be restored.
Until Microsoft provides a root cause or a restoration time, the outage remains an investigation in progress — one affecting connectivity across Microsoft 365, in any region, according to Microsoft.
Clara Ledger
Markets Desk, The Library Media
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