Some users may have been unable to access their mailbox via Exchange ActiveSync (EAS)

Timeline (UK time)

1. 19 Sep 2026, 15:38 BST ✓ Operational

   Title: Some users may have been unable to access their mailbox via Exchange ActiveSync (EAS) User impact: Users may have been unable to access their mailbox via EAS. Final status: We've determined that a potential networking issue may have caused a section of mailbox database infrastructure to perform below acceptable performance thresholds. Our automated recovery systems redirected user traffic to alternate infrastructure and we confirmed that impact was remediated after a period of monitoring service health. Scope of impact: Impact was specific to users located in Europe attempting to access their mailbox via EAS. Start time: Saturday, September 19, 2026, at 1:00 PM UTC End time: Saturday, September 19, 2026, at 1:42 PM UTC Root cause: A potential networking issue may have caused a section of mailbox database infrastructure to perform below acceptable performance thresholds. Next steps: We're analyzing performance data and trends on the affected infrastructure to help prevent this problem from happening again. This is the final update for the event.

2. 19 Sep 2026, 14:53 BST ✓ Operational

   Title: Some users may be unable to access their mailbox via Exchange ActiveSync (EAS) User impact: Users may be unable to access their mailbox via EAS. Current status: We're reviewing service monitoring telemetry to isolate the root cause and develop a remediation plan. Scope of impact: Impact is specific to users located in Europe attempting to access their mailbox via EAS. Next update by: Saturday, September 19, 2026, at 4:00 PM UTC

3. 19 Sep 2026, 14:21 BST ✓ Operational

   Title: Potential issues accessing mailboxes via one or more connection methods User impact: Users may experience errors or failures when accessing their mailbox via one or more Exchange Online connection methods. Current status: We're investigating a potential issue and checking for impact to your organization. We'll provide an update within 60 minutes.