Some users may be unable to send or receive email from the Outlook mobile app on their devices

Title: Some users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: We're continuing to monitor the progress of the deployment as it continues to saturate the affected environment. We'll provide a timeline for the completion of the deployment as one becomes available.

Scope of impact: Some users attempting to send or receive email from the Outlook mobile app may be impacted.

Start time: Thursday, August 14, 2025, at 7:32 AM UTC

Root cause: A recent build update introduced a condition where, upon encountering a typical transient failure, an exception is generated for a subset of users that results in the sync job responsible for syncing outbound and inbound mail being placed in a quarantine state, resulting in syncs being delayed for a 12-hour interval.

Next update by: Monday, August 25, 2025, at 9:00 PM UTC

Title: Some users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: We’ve initiated the deployment of our permanent fix to the affected environment. We’ll continue monitoring the deployment as it progresses to better assess and provide an estimation for its completion and impact resolution by our next update.

Scope of impact: Some users attempting to send or receive email from the Outlook mobile app may be impacted.

Start time: Thursday, August 14, 2025, at 7:32 AM UTC

Root cause: A recent build update introduced a condition where, upon encountering a typical transient failure, an exception is generated for a subset of users that results in the sync job responsible for syncing outbound and inbound mail being placed in a quarantine state, resulting in syncs being delayed for a 12-hour interval.

Next update by: Thursday, August 21, 2025, at 11:30 PM UTC

Title: Some users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: Our initial fix, a configuration change intended to change the configured delay interval to one hour, so the sync recovers more quickly to provide relief, wasn’t successful during our testing and validation. We're working to determine if there's still a method to implement this successfully. In parallel, our permanent fix will begin deployment with our next scheduled communication update, at which time we anticipate having a timeline for deployment completion and impact resolution.

Scope of impact: Some users attempting to send or receive email from the Outlook mobile app may be impacted.

Start time: Thursday, August 14, 2025, at 7:32 AM UTC

Root cause: A recent build update introduced a condition where, upon encountering a typical transient failure, an exception is generated for a subset of users that results in the sync job responsible for syncing outbound and inbound mail being placed in a quarantine state, resulting in syncs being delayed for a 12-hour interval.

Next update by: Wednesday, August 20, 2025, at 11:30 PM UTC

Title: Some users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: We've confirmed that a recent build update introduced a condition where, upon encountering a typical transient failure, an exception is generated for a subset of users that results in the sync job responsible for syncing outbound and inbound mail being placed in a quarantine state, resulting in syncs being delayed for a 12-hour interval, which is why some users already saw recovery. We're working on two fixes to remediate impact. The first fix is a configuration change to provide relief that will change the configured delay interval to one hour, so the sync recovers more quickly. The second fix addresses the condition to ensure the syncs will no longer enter the quarantine state. We anticipate our configuration change will be ready by our next scheduled update, after which we expect to have a timeline for the long-term fix.

Scope of impact: Some users attempting to send or receive email from the Outlook mobile app may be impacted.

Start time: Thursday, August 14, 2025, at 7:32 AM UTC

Root cause: A recent build update introduced a condition where, upon encountering a typical transient failure, an exception is generated for a subset of users that results in the sync job responsible for syncing outbound and inbound mail being placed in a quarantine state, resulting in syncs being delayed for a 12-hour interval.

Next update by: Tuesday, August 19, 2025, at 11:30 PM UTC

Title: Some users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: While our monitoring indicates that the frequency of occurrences of the impact may be reduced, the majority of the impact is ongoing. We're continuing our investigation into the previously mentioned service change that we suspect is responsible for the impact to isolate the root cause of the mailbox crashes and identify a path to remediation.

Scope of impact: Some users attempting to send or receive email from the Outlook mobile app may be impacted.

Next update by: Monday, August 18, 2025, at 11:30 PM UTC

Title: Some users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: We've identified a recent service change, designed to improve the efficiency of mailbox syncs, that may be causing impact. Our mailbox telemetry suggests that while the service change has improved mailbox sync times for most users, it's causing some mailboxes to crash. The number of crashes is dropping over time without us having taken any action, so we're continuing to monitor our telemetry to determine whether the service returns to a healthy state. In the meantime, we're investigating why the service change may be causing the mailboxes to crash while exploring options to expedite the restoration of service.

Scope of impact: Some users attempting to send or receive email from the Outlook mobile app may be impacted.

Next update by: Monday, August 18, 2025, at 7:30 PM UTC

Title: Users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: We're reaching out to affected users to provide error logs from those who were most recently affected to assist with the investigation into the source of the issue and determine our next steps.

Scope of impact: Users attempting to send or receive email from the Outlook mobile app may be impacted.

Next update by: Monday, August 18, 2025, at 4:30 PM UTC

Title: Users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: Our review of the provided case details and error logs is inconclusive however we continue our investigation to determine our next steps.

Scope of impact: Users attempting to send or receive email from the Outlook mobile app may be impacted.

Next update by: Monday, August 18, 2025, at 11:30 AM UTC

Title: Users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: Our review of the provided case details and error logs is ongoing to isolate the root cause of impact.

Scope of impact: Users attempting to send or receive email from the Outlook mobile app may be impacted.

Next update by: Monday, August 18, 2025, at 9:30 AM UTC

Title: Users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: We're continuing to review the provided case details and error logs as we work to better illuminate the underlying cause of impact and help inform our next steps.

Scope of impact: Users attempting to send or receive email from the Outlook mobile app may be impacted.

Next update by: Monday, August 18, 2025, at 7:30 AM UTC

Title: Users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

Current status: We're investigating the provided case details and error logs to better understand the cause of impact and determine our next troubleshooting steps.

Scope of impact: Users attempting to send or receive email from the Outlook mobile app may be impacted.

Next update by: Monday, August 18, 2025, at 5:30 AM UTC

Title: Users may be unable to send or receive email from the Outlook mobile app on their devices

User impact: Users may be unable to send or receive email from the Outlook mobile app on their devices.

More info: Affected users would be utilizing Hybrid Modern Authentication (HMA).

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.