Some users may be unable to search in Exchange Online

Title: Some users may be unable to search in Exchange Online User impact: Users may have been unable to search in Exchange Online. More info: Users may have been unable to complete searches using Outlook on the web or either the classic or new Outlook desktop apps. Final status: We've confirmed after further analysis of search traffic patterns during the impact window that the problem was the result of a portion of Exchange Online infrastructure responsible for search functionality experiencing lower than expected availability, preventing some users from searching during peak hours. Our code fix has successfully recovered search function availability, and we've confirmed after an extended period of monitoring that the impact has been remediated by our actions. Scope of impact: Some users in the United Kingdom who were attempting to complete searches using Outlook on the web or either the classic or new Outlook desktop apps may have been impacted. Start time: Tuesday, September 8, 2026, at 8:00 AM UTC End time: Tuesday, September 8, 2026, at 4:30 PM UTC Root cause: A portion of Exchange Online infrastructure responsible for search functionality experiencing lower than expected availability, which prevented some users from searching during peak hours. Next steps: - We're continuing to monitor the affected infrastructure to verify no further optimizations are necessary to prevent this issue from reoccurring. This is the final update for the event.

Title: Some users may be unable to search in Exchange Online User impact: Users may be unable to search in Exchange Online. More info: Users may be unable to complete searches using Outlook on the web or either the classic or new Outlook desktop apps. Current status: We’ve developed and deployed a code change which is intended to improve availability and reduce the aforementioned instability that occurs during peak traffic periods. Additionally, we’re monitoring the service health telemetry to validate the mitigations effectiveness, which will determine if additional troubleshooting will be required. Scope of impact: Some users in the United Kingdom who are attempting to complete searches using Outlook on the web or either the classic or new Outlook desktop apps may be impacted. This section may be updated as the investigation continues. Next update by: Wednesday, September 9, 2026, at 6:30 PM UTC

Title: Some users may be unable to search in Exchange Online User impact: Users may be unable to search in Exchange Online. More info: Users may be unable to complete searches using Outlook on the web or either the classic or new Outlook desktop apps. Current status: We've identified that the issue subsides during off-peak hours, suggesting that the majority of impacted users may no longer be experiencing the issue. We're further investigating a portion of Exchange Online infrastructure responsible for search functionality to aid in identifying the underlying root cause, while we also investigate if any recent deployments could be contributing to impact. Scope of impact: Some users in the United Kingdom who are attempting to complete searches using Outlook on the web or either the classic or new Outlook desktop apps may be impacted. Next update by: Wednesday, September 9, 2026, at 6:30 AM UTC

Title: Some users may be unable to search in Exchange Online User impact: Users may be unable to search in Exchange Online. More info: Users may be unable to complete searches using Outlook on the web or either the classic or new Outlook desktop apps. Current status: Our analysis of the telemetry leads us to suspect that the impact may be resulting from an existing stability issue. We're continuing to investigate the traffic patterns to confirm this theory while, in parallel, we're monitoring to confirm whether the issue subsides during off-peak hours. Scope of impact: Some users in the United Kingdom who are attempting to complete searches using Outlook on the web or either the classic or new Outlook desktop apps may be impacted. This section may be updated as the investigation continues. Next update by: Wednesday, September 9, 2026, at 2:00 AM UTC

Title: Some users may be unable to search in Exchange Online User impact: Users may be unable to search in Exchange Online. More info: Users may be unable to complete searches using Outlook on the web or either the classic or new Outlook desktop apps. Current status: We're reviewing service health telemetry to help determine our next troubleshooting steps. Scope of impact: Some users in the United Kingdom who are attempting to complete searches using Outlook on the web or either the classic or new Outlook desktop apps may be impacted. This section may be updated as the investigation continues. Next update by: Tuesday, September 8, 2026, at 5:00 PM UTC

Title: Some users may be unable to search in Exchange Online User impact: Users may be unable to search in Exchange Online. More info: Users may be unable to complete searches using Outlook on the web or either the classic or new Outlook desktop apps. Current status: We're investigating a potential issue with Exchange Online and checking for impact to your organization. We'll provide an update within 30 minutes.