Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods.

Title: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. User impact: Users may have been intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may have intermittently impacted some users who attempted to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Final status: We've confirmed that the deployment of the code change has completed saturation, and after a period of monitoring service health telemetry, we've observed the errors associated with the impact have ceased and the issue is resolved. Scope of impact: This issue intermittently impacted some users attempting to access their Exchange Online mailboxes, with a smaller subset of users persistently unable to access their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. Start time: Tuesday, March 17, 2026, at 2:00 PM UTC End time: Wednesday, April 15, 2026, at 11:00 PM UTC Root cause: A service component that facilitates notification generation and delivery wasn't processing requests as expected, which resulted in impact. Next steps: - We're entering an extended period of monitoring to ensure the program we've implemented to identify and restart the notification service when persistent errors are detected successfully prevents this issue from reoccurring. This is the final update for the event.

Title: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. User impact: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may intermittently impact some users attempting to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Current status: We're continuing to monitor our fix deployment as it saturates throughout the remaining 10 percent of the affected environment. Many previously impacted users will begin to experience significant impact relief as this saturation finalizes. In tandem, we're implementing a program to identify and restart the Notification service as persistent errors are identified.  Scope of impact: This issue intermittently impacts some users attempting to access their Exchange Online mailboxes, with a smaller subset of users persistently unable to access their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. This section may be updated as our investigation progresses. Start time: Tuesday, March 17, 2026, at 2:00 PM UTC Root cause: A service component that facilitates notification generation and delivery isn't processing requests as expected, which is resulting in impact. Next update by: Friday, April 17, 2026, at 8:00 PM UTC

Title: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. User impact: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may intermittently impact some users who attempt to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Current status: Our deployment has reached 90 percent of the affected environment and we expect it will complete by our next scheduled update. We'll monitor the results of this fix while continuing to implement a program to identify and restart the Notification service as errors are identified. Scope of impact: Impact may occur intermittently for some users with a smaller small set of users persistently being unable to access their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. This section may be updated as our investigation progresses. Root cause: A service that facilitates notification generation and delivery isn't processing requests as expected, resulting in impact. Next update by: Tuesday, April 14, 2026, at 8:00 PM UTC

Title: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. User impact: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may intermittently impact some users who attempt to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Current status: We're continuing to monitor the deployment of our long-term fix while we also continue to implement a program to identify and restart the Notification service as errors are identified. These actions will help us limit further impact while the fix deploys and we'll provide a resolution timeline once available. Scope of impact: Impact may occur intermittently for approximately 3,000 users with a smaller set of users persistently being unable to access their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. This section may be updated as our investigation progresses. Root cause: A service that facilitates notification generation and delivery isn't processing requests as expected, resulting in impact. Next update by: Monday, April 13, 2026, at 6:30 PM UTC

Title: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. User impact: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may intermittently impact some users who attempt to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Current status: After further analysis, we've isolated that this issue intermittently impacts approximately 3,000 users with a smaller set of users persistently impacted, and we've updated the "Scope of impact" in our communications to reflect this new scope. We're continuing to monitor the deployment of our long-term fix while we also continue to implement a program to identify and restart the Notification service as errors are identified. These actions will help us limit further impact while the fix deploys. Scope of impact: Impact may occur intermittently for approximately 3,000 users with a smaller set of users persistently being unable to access their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. This section may be updated as our investigation progresses. Estimated time to resolve: We expect the fix deployment to complete by Friday, April 17, 2026. Root cause: A service that facilitates notification generation and delivery isn't processing requests as expected, resulting in impact. Next update by: Friday, April 10, 2026, at 8:00 PM UTC

Title: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. User impact: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may intermittently impact some users who attempt to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Current status: We've completed the development of a long term fix and are monitoring as the release progresses. We've implemented a program to identify and restart the Notification service as errors are identified to limit further impact while the fix deploys. Scope of impact: Impact may occur intermittently for some users accessing their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. This section may be updated as our investigation progresses. Estimated time to resolve: We expect the fix deployment to complete by Friday, April 17, 2026. Root cause: A service that facilitates notification generation and delivery isn't processing requests as expected, resulting in impact. Next update by: Friday, April 10, 2026, at 8:00 PM UTC

Title: Users may have been intermittently unable to access their Exchange Online mailboxes in some connection methods. User impact: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may intermittently impact some users who attempt to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Current status: We've confirmed that the Notification Broker service restarted throughout the affected infrastructure and is successfully alleviating the majority of impact for users. We're also developing a code change and a revert on a recent service update to address additional issues that are contributing to impact while we continue our investigation into the underlying root cause. Scope of impact: Impact may occur intermittently for some users accessing their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. This section may be updated as our investigation progresses. Next update by: Tuesday, April 7, 2026, at 8:00 PM UTC

Title: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods User impact: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may intermittently impact some users who attempt to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Current status: We're finalizing our process to restart the Notification Broker service across the affected infrastructure, which we anticipate may remediate the impact. In parallel, we're assessing options to implement long-term mitigation and telemetry to prevent further instances of impact while we continue our investigation into the underlying root cause. Scope of impact: Impact may occur intermittently for some users accessing their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. This section may be updated as our investigation progresses. Next update by: Friday, April 3, 2026, at 8:00 PM UTC

Title: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods User impact: Users may be intermittently unable to access their Exchange Online mailboxes in some connection methods. More info: This issue may intermittently impact some users who attempted to access the Exchange Online service through the Outlook mobile apps or the new Outlook for Mac desktop client. Current status: We've received reports from affected tenants that the impact scenario originally communicated through SHD EX1256020 is still ongoing. We're working to restart the Notification Broker service on affected portions of Exchange Online service infrastructure to remediate impact while we continue our analysis into the underlying root cause. Scope of impact: Impact may occur intermittently for some users accessing their Exchange Online mailboxes in the Outlook mobile apps or the new Outlook for Mac desktop client. This section may be updated as our investigation progresses. Next update by: Thursday, April 2, 2026, at 11:30 PM UTC