Some users may be intermittently unable to access the Exchange Online service through multiple connection methods

Title: Some users may be intermittently unable to access the Exchange Online service through multiple connection methods

User impact: Users may be intermittently unable to access the Exchange Online service through multiple connection methods.

More info: This issue impacts the following connection methods, although impact may not be limited to them:

- Outlook on the web
- Outlook mobile app
- Outlook on Mac devices

Current status: While we're observing some recovery after rolling back the impacting change, we're exploring options to expedite the resolution.

Scope of impact: This issue may impact any user based in the United States, France, and United Kingdom regions. This information may be updated as our investigation continues.

Root cause: A recent code regression is causing crashes on a portion of mailbox infrastructure that handles access requests from Outlook on the web, New Outlook, Outlook for Mac, and mobile apps.

Next update by: Friday, January 23, 2026, at 7:00 PM UTC

Title: Users may experience errors when accessing or loading Exchange Online via one or more clients or connection methods

User impact: Users may experience errors when accessing or loading Exchange Online via one or more clients or connection methods.

More info: The following impacted clients and connection methods include but aren't limited to:

- Outlook on the web
- Outlook mobile app
- Outlook on MAC devices

Current status: We’ve identified that a recent code regression in the Exchange Online service is causing unexpected errors and service instability in Outlook on the web, New Outlook, Mac and Mobile clients. The issue is linked to backported updates that affected Information Protection features, leading to increased crashes within the affected infrastructure. We've initiated a rollback of the affected changes and we’re continuing to monitor performance across all environments to ensure full recovery.

Scope of impact: This issue may impact any user within your organization served via the affected region(s): United States, France and United Kingdom. This information may be updated as our investigation continues.

Root cause: A recent code regression introduced changes in Exchange Online service resulting in impact. This regression is causing crashes on some of the affected mailbox infrastructure affecting Outlook on the web, New Outlook, Mac and Mobile clients.

Next update by: Friday, January 23, 2026, at 4:30 PM UTC

Title: Some users may be unable to access or load Outlook on the web

User impact: Users may be unable to access or load Outlook on the web.

Current status: We’ve completed a rollback of recent changes and restored the service to a stable configuration. Our monitoring shows that availability is improving across affected regions, but some environments are still experiencing issues. Additionally, we've identified an update that caused unexpected behavior and are working on a fix to deploy once fully validated.

Scope of impact: This issue may impact any user within your organization served via the affected region(s): United States, France and United Kingdom. This information may be updated as our investigation continues.

Next update by: Friday, January 23, 2026, at 2:30 PM UTC

Title: Some users may be unable to access or load Outlook on the web

User impact: Users may be unable to access or load Outlook on the web.

Current status: We've received reports that users may be unable to access or load Outlook on the web, and we're reviewing service monitoring telemetry to understand the scope of impact.

Scope of impact: This issue may impact any user within your organization served via the affected region(s): United States, France and United Kingdom. This information may be updated as our investigation continues.

Next update by: Friday, January 23, 2026, at 12:30 PM UTC