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Microsoft Exchange Online Outage Affecting Multiple Connection Methods Due to Authentication Misconfiguration

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1 unique sources, 2 articles

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Microsoft is addressing an ongoing Exchange Online outage affecting multiple connection methods, including Outlook on the web, Outlook desktop, and Exchange ActiveSync. The issue, tracked under incident ID EX1253275, stems from a code conflict in a recent deployment related to authentication support. The misconfiguration causes intermittent access problems for some users. Microsoft has identified a section of service infrastructure not processing traffic efficiently and is making configuration changes to remediate the impact. The company expects the issue to be fully resolved by the next scheduled update. Other connection methods remain unaffected. The incident was first acknowledged on the day of the article at 06:42 AM UTC. While the exact number of users and regions impacted is not specified, the issue has been flagged as critical in the Microsoft 365 admin center. Additionally, Microsoft is investigating a separate outage affecting the Microsoft 365 Copilot web sign-in page and Copilot web clients.

Timeline

  1. 08.01.2026 14:45 2 articles · 2mo ago

    Microsoft Exchange Online IMAP4 Access Disruption Due to Authentication Misconfiguration

    Microsoft is addressing an ongoing Exchange Online outage affecting multiple connection methods, including Outlook on the web, Outlook desktop, and Exchange ActiveSync. The issue, tracked under incident ID EX1253275, stems from a code conflict in a recent deployment related to authentication support. The misconfiguration causes intermittent access problems for some users. Microsoft has identified a section of service infrastructure not processing traffic efficiently and is making configuration changes to remediate the impact. The company expects the issue to be fully resolved by the next scheduled update. Other connection methods remain unaffected. The incident was first acknowledged on the day of the article at 06:42 AM UTC. While the exact number of users and regions impacted is not specified, the issue has been flagged as critical in the Microsoft 365 admin center. Additionally, Microsoft is investigating a separate outage affecting the Microsoft 365 Copilot web sign-in page and Copilot web clients.

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