Microsoft Exchange Online outage causes email failures, auth issues
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Microsoft has confirmed it is investigating a widespread service incident affecting Exchange Online, with customers reporting authentication failures, email delays, and delivery errors across multiple tenants. The issue appears to be impacting sign-in flows and mailbox access, causing intermittent disruptions for both end users and automated services relying on Exchange Online.
Affected symptoms include the inability to authenticate to Outlook Web Access (OWA), delays in message delivery, and failures when sending or receiving mail. Some tenants are also reporting issues with calendar availability and shared mailbox access, suggesting the problem extends beyond simple transport queues and into the authentication layer of the service.
While the company has not yet published a root cause, the incident is being tracked under an active service health advisory in the Microsoft 365 admin center. Microsoft has stated that it is rerouting traffic and applying targeted mitigations to restore service for impacted regions.
Key details for admins and users:
- Service degradation is limited to Exchange Online; other Microsoft 365 workloads appear unaffected.
- The issue is not tied to any client-side configuration, so clearing cache or reinstalling the Outlook app will not resolve the fault.
- Administrators should monitor the Microsoft 365 Service Health Dashboard for the latest incident updates and estimated resolution times.
- No workaround has been provided by Microsoft at this time; impacted users are advised to retry after a short delay.
As with most cloud-side outages, there is little that tenants can do beyond waiting for the service to recover. However, it is worth checking if your tenant is part of the affected region and reviewing any recent authentication logs for unusual failures that may align with the incident window.
Source: BleepingComputer
Has your tenant experienced any authentication or mail-delivery delays today, and are you relying on any manual retry workflows to keep business moving?
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