Outage in Microsoft 365
Some users may be unable to access their Exchange Online mailbox through Outlook on the web
Resolved Minor
May 27, 2026 - Started 2 months ago
- Lasted about 2 months
Incident Report
Summary AI Generated
On May 27, 2026, some Exchange Online users in Europe, the Middle East, and Africa were unable to access their mailboxes through Outlook on the web for approximately two hours (6:12 PM – 8:17 PM UTC). The issue was caused by a portion of infrastructure responsible for handling mailbox access requests performing below acceptable thresholds. The service self-recovered, and Microsoft confirmed full resolution with no further action required.
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.
Components affected
Exchange OnlineTrusted by 1,000+ teams
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Latest Updates ( sorted recent to last )
2 months ago - at 05/27/2026 10:21PM
Title: Some users may be unable to access their Exchange Online mailbox through Outlook on the web
User impact: Users may have been unable to access their Exchange Online mailbox through Outlook on the web.
Final status: While we were in the process of analyzing service health telemetry, system monitoring indicated that the service had returned to normal health. We've confirmed that the issue is no longer occurring and we'll continue to monitor the service to ensure that the problem doesn't happen again.
Scope of impact: Some users in Europe, the Middle East, and Africa who attempted to access their mailboxes through Outlook on the web may have been impacted.
Start time: Wednesday, May 27, 2026, at 6:12 PM UTC
End time: Wednesday, May 27, 2026, at 8:17 PM UTC
Root cause: A portion of infrastructure responsible for facilitating mailbox access requests was performing below acceptable thresholds which resulted in impact.
Next steps:
- We're continuing to analyze the affected infrastructure to determine what caused it to fall into an unhealthy state so we can address any insufficiencies and prevent this from happening again.
This is the final update for the event.
2 months ago - at 05/27/2026 08:45PM
Title: Some users may be unable to access their Exchange Online mailbox through Outlook on the web
User impact: Users may be unable to access their Exchange Online mailbox through Outlook on the web.
Current status: Our investigation of service health telemetry determined that a portion of infrastructure responsible for facilitating mailbox access requests is performing below acceptable thresholds, which is resulting in impact. We're observing availability returning as the service appears to be self-recovering, and we're monitoring to ensure no actions are needed to fully resolve the impact.
Scope of impact: Some users in Europe, the Middle East, and Africa attempting to access their mailboxes through Outlook on the web may be impacted.
Start time: Wednesday, May 27, 2026, at 6:12 PM UTC
Root cause: A portion of infrastructure responsible for facilitating mailbox access requests is performing below acceptable thresholds and resulting in impact.
Next update by: Wednesday, May 27, 2026, at 10:30 PM UTC
2 months ago - at 05/27/2026 06:44PM
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.
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