Some users may see intermittent failures when accessing Exchange Online through Representational State Transfer (REST)

Title: Some users may see intermittent failures when accessing Exchange Online through Representational State Transfer (REST) User impact: Users may have experienced intermittent errors or failures when accessing Exchange Online through REST. Final status: We've confirmed that a directory service component configuration change intended to further optimize the service was resulting in impact. We've fully disabled the offending change and verified through internal monitoring that impact is remediated. Scope of impact: Impact may have intermittently occurred for some users who were attempting to access Exchange Online through Representational State Transfer (REST). Start time: Wednesday, October 14, 2026, at 5:55 PM UTC End time: Tuesday, October 27, 2026, at 11:48 PM UTC Root cause: A directory service component configuration change intended to further optimize the service was resulting in impact. Next steps: -We're reviewing our feature update testing and validation methods to better identify the potential for impact prior to deployment so we can prevent similar issues in the future, and to improve our pre-deployment update testing processes.

Title: Some users may see intermittent failures when accessing Exchange Online through Representational State Transfer (REST) User impact: Users may experience intermittent errors or failures when accessing Exchange Online through REST. Current status: We've successfully validated that disabling the change remediates impact with no unforeseen side effects. We're continuing to roll out this change in order to fully remediate impact, and we expect that it will complete by our next scheduled update. Scope of impact: Impact may intermittently occur for some users who are attempting to access Exchange Online through REST. This section may be updated as the investigation continues. Next update by: Wednesday, October 28, 2026, at 1:00 AM UTC

Title: Some users may experience intermittent errors or failures when accessing Exchange Online through REST APIs User impact: Users may experience intermittent errors or failures when accessing Exchange Online through REST APIs. Current status: We're continuing to disable the recent service change intended to optimize directory functionality in additional selected affected environments while monitoring service telemetry to validate whether this action successfully alleviates impact. If successful, we'll proceed with disabling the change throughout the remaining affected environments to fully remediate impact. We'll provide a resolution timeline once available. Scope of impact: Impact may occur intermittently for users attempting to access Exchange Online through REST APIs. Next update by: Tuesday, October 27, 2026, at 11:30 PM UTC

Title: Some users may experience intermittent errors or failures when accessing Exchange Online through REST APIs User impact: Users may experience intermittent errors or failures when accessing Exchange Online through REST APIs. Current status: We're continuing to disable the recent service change intended to optimize directory functionality in additional selected affected environments and monitoring service telemetry to validate whether this action alleviates impact. If successful, we'll proceed with disabling the change throughout the remaining affected environments to fully remediate impact. Scope of impact: Impact may occur intermittently for users attempting to access Exchange Online through REST APIs. Next update by: Tuesday, October 27, 2026, at 9:30 PM UTC

Title: Some users may experience intermittent errors or failures when accessing Exchange Online through REST APIs User impact: Users may experience intermittent errors or failures when accessing Exchange Online through REST APIs. Current status: We've identified that a recent service change intended to optimize directory functionality may have introduced an issue with how Exchange Online Representational State Transfer (REST) API requests are processed, resulting in intermittent errors or failures. We're testing this theory by disabling the change in a portion of the affected environments and monitoring service telemetry to determine whether this action alleviates impact. If successful, we'll proceed with disabling the change throughout the remaining affected environments to fully remediate impact. Scope of impact: Impact may occur intermittently for users attempting to access Exchange Online through REST APIs. Next update by: Tuesday, October 27, 2026, at 7:30 PM UTC

Title: Some users may experience intermittent errors or failures when accessing Exchange Online through REST APIs User impact: Users may experience intermittent errors or failures when accessing Exchange Online through REST APIs. Current status: We're continuing to review service telemetry and recent service changes in an effort to isolate the source of this issue and determine an appropriate remediation action. Scope of impact: Impact may occur intermittently for users attempting to access Exchange Online through REST APIs. Next update by: Tuesday, October 27, 2026, at 5:30 PM UTC

Title: Some users may experience intermittent errors or failures when accessing Exchange Online through REST APIs User impact: Users may experience intermittent errors or failures when accessing Exchange Online through REST APIs. Current status: We're investigating an issue in which users may experience intermittent errors or failures when accessing Exchange Online through REST APIs. We're reviewing service telemetry to determine the underlying cause and identify the most effective remediation action. We'll provide an update within 30 minutes.