Some users may be unable to send or receive new Exchange Online email through the native iOS mail app

Title: Some users may be unable to send or receive new Exchange Online email through the native iOS mail app User impact: Users may have been unable to send or receive new Exchange Online email through the native iOS mail app. Final status: We reverted the authentication component changes utilized for Exchange ActiveSync and validated in our telemetry as well as with affected users that the impact was remediated. Scope of impact: Some users attempting to send or receive new Exchange Online email through the native iOS mail app were impacted. Start time: Monday, August 17, 2026, at 11:38 PM UTC End time: Tuesday, August 18, 2026, at 7:15 AM UTC Root cause: Recent changes to an authentication component utilized for Exchange ActiveSync were causing connection failures. Next steps: We're continuing our analysis of the recent changes to isolate what triggered the initial impact which will help us in refining our update review processes to avoid impact in the future. This is the final update for the event.

Title: Some users may be unable to send or receive new Exchange Online email through the native iOS mail app User impact: Users may be unable to send or receive new Exchange Online email through the native iOS mail app. Current status: After reviewing the logs, we identified that there were recent changes to an authentication component utilized for Exchange ActiveSync that is causing connection failures. We're working to revert the problematic changes, which we anticipate should remediate the impact by the time of our next scheduled update, at which point we'll reach out to confirm with a subset of impacted users. Scope of impact: Some users attempting to send or receive new Exchange Online email through the native iOS mail app are impacted. Start time: Monday, August 17, 2026, at 11:38 PM UTC Root cause: Recent changes to an authentication component utilized for Exchange ActiveSync are causing connection failures. Next update by: Tuesday, August 18, 2026, at 9:00 AM UTC

Title: Some users may be unable to send or receive new Exchange Online email through the native iOS mail app User impact: Users may be unable to send or receive new Exchange Online email through the native iOS mail app. Current status: We're continuing our analysis of service-side logs and Exchange ActiveSync logs collected from impacted users to understand the source of the issue and determine our next troubleshooting steps. Scope of impact: Some users attempting to send or receive new Exchange Online email through the native iOS mail app may be impacted. This information may be updated as our investigation continues. Next update by: Tuesday, August 18, 2026, at 7:00 AM UTC

Title: Some users may be unable to send or receive new Exchange Online email through the native iOS mail app User impact: Users may be unable to send or receive new Exchange Online email through the native iOS mail app. Current status: We're reviewing service logs, telemetry, and contextual details provided by impacted users to gain insight into the underlying source of impact and determine our next steps. Scope of impact: Some users attempting to send or receive new Exchange Online email through the native iOS mail app may be impacted. This information may be updated as our investigation continues. Next update by: Tuesday, August 18, 2026, at 5:00 AM UTC