Some users may have experienced errors or failures when accessing their mailbox via Outlook on the web

Title: Some users may have experienced errors or failures when accessing their mailbox via Outlook on the web User impact: Users may have experienced errors or failures when accessing their mailbox via Outlook on the web. More info: As a result of this service degradation, users may have also experienced issues accessing the Microsoft Purview and Microsoft Defender portals. Final status: We've determined that a recent service change within the Exchange Online front-end infrastructure caused processes responsible for facilitating user connections to terminate unexpectedly, resulting in impact. We reverted the suspected change and confirmed after a period of monitoring that service health has returned to expected levels and impact has been remediated. Scope of impact: Impact was specific to some users in Europe, Middle East and Africa attempting to access mailboxes via Outlook on the web. Start time: Monday, November 9, 2026, at 6:56 AM UTC End time: Monday, November 9, 2026, at 10:46 AM UTC Root cause: A recent service change affected how user connections were handled, causing some connections to terminate unexpectedly and resulting in impact. Next steps: - We’re reviewing our service change testing and validation procedures to help identify and prevent similar connection issues from occurring in the future. This is the final update for the event.

Title: Some users may experience errors or failures when accessing their mailbox via Outlook on the web User impact: Users may experience errors or failures when accessing their mailbox via Outlook on the web. Current status: We’ve identified that affected requests are failing due to unexpected connection terminations within a section of Exchange Online infrastructure. We’re analyzing the affected connection path to determine why these connections are being unexpectedly terminated, while reviewing network connectivity, infrastructure load, and request routing across the affected environment. In parallel, we're examining recent service configuration changes for any correlation with the failures and comparing telemetry across the affected infrastructure to isolate the underlying cause and determine our next steps toward remediation. Scope of impact: Impact is specific to some users in Europe, Middle East and Africa attempting to access mailboxes via Outlook on the web. Next update by: Monday, November 9, 2026, at 12:00 PM UTC

Title: Some users may experience errors or failures when accessing their mailbox via Outlook on the web User impact: Users may experience errors or failures when accessing their mailbox via Outlook on the web. Current status: We're reviewing service monitoring telemetry to isolate the source of the issue and establish a fix. Scope of impact: Impact is specific to some users in Europe attempting to access mailboxes via Outlook on the web. Next update by: Monday, November 9, 2026, at 10:00 AM UTC

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.