Some users may be unable to open the account view in Outlook on the web

Title: Some users may be unable to open the account view in Outlook on the web User impact: Users may have been unable to open the account view in Outlook on the web. More info: When users attempted to access the account page, the authentication flow failed with the following error: 'AADSTS90002: Tenant 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX' not found. Final status: Following the deployment of our code fix, we've validated with affected users that the code fix has been addressed, and that the impact has been remediated. If users still encounter this problem, they can refresh their Outlook on the web browser session to immediately receive the fix. Scope of impact: Some users who attempted to open the account view in Outlook on the web may have been impacted. Start time: Tuesday, September 22, 2026, at 12:44 PM UTC End time: Wednesday, September 23, 2026, at 2:00 AM UTC Root cause: A code misconfiguration was introduced by a recent service change intended to modernize the Outlook on the web header, resulting in impact. Next steps: - We're further analyzing the recent impacting change to help us improve our pre-deployment tests and validations. This is the final update for the event.

Title: Some users may be unable to open the account view in Outlook on the web User impact: Users may be unable to open the account view in Outlook on the web. More info: When attempting to access the account page, the authentication flow fails with the following error: 'AADSTS90002: Tenant 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX' not found. Check to make sure you have the correct tenant ID and are signing into the correct cloud. Check with your subscription administrator, this may happen if there are no active subscriptions for the tenant.' Current status: We've identified that a code misconfiguration was introduced by a service change intended to modernize the Outlook on the web header, resulting in impact. We've developed and validated a fix to address the code misconfiguration, which we're preparing to deploy to the affected environment. We anticipate the deployment of our fix will begin by our next scheduled communications update. Scope of impact: Some users attempting to open the account view in Outlook on the web may be impacted. This section may be updated as our investigation continues. Start time: Tuesday, September 22, 2026, at 12:44 PM UTC Root cause: A code misconfiguration was introduced by a recent service change intended to modernize the Outlook on the web header, resulting in impact. Next update by: Wednesday, September 23, 2026, at 6:00 PM UTC

Title: Some users may be unable to open the account view in Outlook on the web User impact: Users may be unable to open the account view in Outlook on the web. More info: When attempting to access the account page, the authentication flow fails with the following error: 'AADSTS90002: Tenant 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX' not found. Check to make sure you have the correct tenant ID and are signing into the correct cloud. Check with your subscription administrator, this may happen if there are no active subscriptions for the tenant.' Current status: We're able to reproduce the issue within our internal testing environment, and we're gathering further diagnostic data to aid in our effort to uncover the source of the impact. Scope of impact: Some users attempting to open the account view in Outlook on the web may be impacted. This section may be updated as our investigation continues. Next update by: Tuesday, September 22, 2026, at 11:30 PM UTC

Title: Some users may be unable to open the account view in Outlook on the web User impact: Users may be unable to open the account view in Outlook on the web. More info: When attempting to access the account page, the authentication flow fails with the following error: 'AADSTS90002: Tenant 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX' not found. Check to make sure you have the correct tenant ID and are signing into the correct cloud. Check with your subscription administrator, this may happen if there are no active subscriptions for the tenant.' Current status: We're reviewing data provided by some affected users to determine our next troubleshooting steps. Scope of impact: Some users attempting to open the account view in Outlook on the web may be impacted. This section may be updated as our investigation continues. Next update by: Tuesday, September 22, 2026, at 6:30 PM UTC