Some users may be unable to access their mailboxes through one or more Exchange Online connection methods

Title: Some users may be unable to access their mailboxes through one or more Exchange Online connection methods

User impact: Users may be unable to access their mailboxes through one or more Exchange Online connection methods.

More info: The following connection methods may be affected:

- Messaging API (MAPI)
- Representational State Transfer (REST) API
- Outlook on the web
- Exchange ActiveSync (EAS)

Current status: Our analysis of service logs from the affected infrastructure has identified that a recently enabled configuration change may be resulting in impact. We’re further reviewing the change and associated logs, specifically noting when it was introduced in correlation to the observed start of impact time to confirm our theory. Simultaneously, we’re looking into whether reverting the suspected configuration change will have any adverse effects. We anticipate that the validation of the underlying cause will be completed, and further insight into our troubleshooting actions will be provided by our next scheduled update.

Scope of impact: Some users in Europe, the Middle East, and Africa may be unable to access their mailboxes through one or more Exchange Online connection methods.

Next update by: Thursday, September 25, 2025, at 4:30 AM UTC

Title: Some users may be unable to access their mailboxes through one or more Exchange Online connection methods

User impact: Users may be unable to access their mailboxes through one or more Exchange Online connection methods.

More info: The following connection methods may be affected:

- Messaging API (MAPI)
- Representational State Transfer (REST) API
- Outlook on the web
- Exchange ActiveSync (EAS)

Current status: Our monitoring of service telemetry shows availability has largely recovered, however recent trends show the availability typically drops hourly during peak traffic hours. We're analyzing service logs from the affected infrastructure and identifying any patterns in behavior that correlate with the impact timeline to narrow the scope of our investigation as we continue our efforts to pinpoint the root cause of the impact.

Scope of impact: Some users in Europe, the Middle East, and Africa may be unable to access their mailboxes through one or more Exchange Online connection methods.

Next update by: Thursday, September 25, 2025, at 1:00 AM UTC

Title: Some users may be unable to access their mailboxes through one or more Exchange Online connection methods

User impact: Users may be unable to access their mailboxes through one or more Exchange Online connection methods.

More info: The following connection methods may be affected:

- Messaging API (MAPI)
- Representational State Transfer (REST) API
- Outlook on the web
- Exchange ActiveSync (EAS)

Current status: While we've noted periods of service health recovery during our investigation into the gateway timeouts, we're also observing a consistent pattern of availability dropping hourly, and we're analyzing portions of affected infrastructure to determine what's causing the impact so we can isolate the root cause.

Scope of impact: Some users in Europe, the Middle East, and Africa may be unable to access their mailboxes through one or more Exchange Online connection methods.

Next update by: Wednesday, September 24, 2025, at 9:00 PM UTC

Title: Some users may be unable to access their mailboxes through one or more Exchange Online connection methods

User impact: Users may be unable to access their mailboxes through one or more Exchange Online connection methods.

More info: The following connection methods may be affected:

- Messaging API (MAPI)
- Representational State Transfer (REST) API
- Outlook on the web
- Exchange ActiveSync (EAS)

Current status: We've noted a number of gateway timeouts during our examination of service health telemetry and we're reviewing these to understand what's causing them so we can determine our next steps towards mitigation.

Scope of impact: Some users in Europe, the Middle East, and Africa may be unable to access their mailboxes through one or more Exchange Online connection methods.

Next update by: Wednesday, September 24, 2025, at 7:00 PM UTC

Title: Some users may be unable to access their mailboxes through one or more Exchange Online connection methods

User impact: Users may be unable to access their mailboxes through one or more Exchange Online connection methods.

Current status: We're reviewing service health telemetry that identified this issue to determine which connection methods are impacted and develop our next troubleshooting steps.

Scope of impact: Some users in Europe, the Middle East, and Africa may be unable to access their mailboxes through one or more Exchange Online connection methods.

Next update by: Wednesday, September 24, 2025, at 5:00 PM 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.