Microsoft is currently investigating a service disruption affecting Exchange Online users who are experiencing difficulties accessing their mailboxes through one or more connection methods.
The issue, tracked under Microsoft 365’s service health dashboard, has prompted multiple status updates throughout Monday, March 16, 2026.
Reports began surfacing earlier on Monday, with Microsoft issuing its first formal acknowledgment at 4:26 PM IST. Subsequent updates followed at 4:53 PM and 7:49 PM IST, indicating that the company’s engineering teams are actively working to identify the root cause and restore full service functionality.
The incident affects Exchange Online, Microsoft’s cloud-hosted email and calendaring platform, which serves millions of enterprise and business customers worldwide.
Affected users may find themselves unable to connect to their mailboxes via clients such as Microsoft Outlook (desktop and mobile), Outlook on the Web (OWA), and potentially third-party email clients relying on protocols like MAPI, IMAP, or EWS.
The scope of impact, as described in the advisory, spans one or more connection methods, suggesting that not all access pathways are uniformly affected.
The disruption appears to impact a subset of Exchange Online users, though Microsoft has not yet publicly disclosed the exact number of affected tenants or geographic regions involved.
Organizations that rely heavily on Exchange Online for day-to-day communications, including email workflows, calendar scheduling, and shared mailbox access, may experience intermittent or persistent connectivity failures during this window.
Microsoft’s 365 service health portal has been updated multiple times, with the engineering team working toward resolution. Users and IT administrators are advised to monitor the Microsoft 365 admin center’s Service Health section for real-time updates. The company has committed to providing further updates as the investigation progresses.
As a workaround, administrators may consider directing users to alternative access methods that remain unaffected, such as switching from a desktop client to Outlook on the Web, or vice versa, depending on which connection method is experiencing disruption in their environment.
Microsoft has not yet attributed the disruption to any specific infrastructure change, deployment update, or configuration issue. Further technical details are expected in subsequent updates as the investigation continues.
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