Users may be unable to connect to, or experience degraded functionality with Exchange Online

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We discovered an issue in less than one percent of our infrastructure, where our additional mitigation efforts to resolve impact for Exchange Online did not successfully deploy. The vast majority of impact remains remediated; however, those serviced from the impacted portion of infrastructure may be unable to access previously recovered Outlook connection methods. We remain committed to restoring all services to all users and will continue to carefully monitor our telemetry to ensure recovery. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 6:30 PM UT

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: While monitoring service telemetry closely, we identified a small volume of errors affecting mail flow functionality. We're conducting targeted restarts to reduce the number of errors and alleviate impact. In parallel, we're continuing to analyze service health telemetry to determine if any additional mitigation actions are required to restore normal functionality. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 4:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We're continuing to implement further mitigation actions where required to resolve any outstanding impact associated with this incident. Customer feedback and reports from our telemetry remain positive, and service health is stable. While this work is underway, we're actively monitoring the service closely to ensure stability is consistent. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 2:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We're performing additional remediation efforts where necessary to address any remaining impact from this incident. Reports from telemetry data and customer feedback are aligned, indicating a sustained recovery. We're actively monitoring the situation closely to ensure impact is completely mitigated. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 12:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We're continuing to closely monitor the service to ensure sustained stability, and signals from telemetry and customer feedback remain positive. In parallel, we're conducting additional remediation actions where required to resolve any lingering residual impact. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 10:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We've confirmed that our services remain stable, and both telemetry and customer reports indicate that the issue has been largely mitigated. We're continuing to address any lingering issues while we remain engaged in an extended monitoring period to validate sustained recovery. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 8:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: Our recovery metrics remain positive, with monitoring continuing to indicate that the service is stable and there is a constant reduction in the number of affected users. We’re continuing to validate recovery through targeted remediation actions and service health checks. We’ll maintain targeted monitoring and validation actions to confirm recovery outcomes and identify any remaining impact. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 6:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: Ongoing monitoring continues to show positive recovery progress, with impact no longer observed for most previously affected users. We’re continuing to monitor service health and implement targeted remediation efforts to validate recovery progress and help ensure ongoing service stability. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 4:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We continue to observe positive recovery trends through ongoing monitoring, with most affected users no longer experiencing disruption. We remain focused on identifying and resolving any remaining issues while implementing targeted mitigations to support a stable and consistent user experience. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 2:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We've confirmed that the majority of users remain mitigated. We're continuing to advance several workstreams as we work toward full resolution for all users and in parallel, we're maintaining enhanced monitoring throughout this work to ensure service stability. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Thursday, September 3, 2026, at 12:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We’ve completed a restart of affected Outlook on the web infrastructure, and service telemetry indicates that the majority of users have recovered. We’re continuing to closely monitor service health as we roll out more durable fixes designed to address the underlying conditions contributing to the impact. In parallel, we’re working directly with affected users and examining reports of continued impact to gather additional diagnostic information and identify any remaining issues. We remain focused on fully restoring service for all affected users and will continue deploying our fixes, investigating reports of impact, and monitoring service health until we’re confident the issue is fully resolved. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Wednesday, September 2, 2026, at 10:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We recognize that while service is restored for most customers, the remaining issues are disruptive for those still impacted. We are prioritizing fully resolving the issue for all customers. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Wednesday, September 2, 2026, at 8:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. - Users may be unable to sign in to Outlook on the web. Current status: We’re working on additional mitigation measures for the portion of infrastructure which have not yet returned to healthy service levels after deployment of our primary remediation. Service availability remains above 99 percent and our monitoring shows impact is resolved for the majority of users. We remain engaged and committed to fully resolving this issue for all users. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Wednesday, September 2, 2026, at 6:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. Current status: Service availability remains stable above 99%, and telemetry indicates sustained recovery across the affected environments. The primary remediation has been deployed across the majority of impacted infrastructure, with remaining deployment and validation activities progressing as expected. Most previously affected users should no longer experience issues related to this event, though a small subset may continue to see intermittent impact while final recovery validation is completed. Our remaining efforts are focused on validating sustained recovery and identifying any remaining infrastructure requiring remediation. Enhanced monitoring remains in place as we continue recovery validation activities. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Wednesday, September 2, 2026, at 5:30 PM UTC

Our telemetry indicates service availability remains stable above 99 percent, and we expect the majority of users should no longer be seeing impact from this issue. Our continued focus is on balancing the implementation of our fixes across remaining portions of affected infrastructure to ensure persistent recovery, with added attention on ensuring withstanding recovery of scenarios dependent on REST and Graph API connection methods. This quick update is designed to give the latest information on this issue. Next update by: Wednesday, September 2, 2026, at 4:30 PM UTC

We're observing service availability recovering to above 99 percent across the affected environments, and we expect the majority of previously affected users should no longer be seeing impact from this issue. Our continued focus is on balancing the implementation of our fixes across remaining portions of affected infrastructure to ensure persistent recovery. This quick update is designed to give the latest information on this issue. Next update by: Wednesday, September 2, 2026, at 4:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Users can't download email message attachments through any Exchange Online connection method. - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. - Users may be unable to use room finder in Outlook calendars. Current status: Based on our telemetry, we expect a small subset of users may still see impact across the listed scenarios, though we're continuing our work to balance the implementation of our fixes across the infrastructure to achieve withstanding recovery. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Wednesday, September 2, 2026, at 4:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: We're continuing to closely monitor service health as we carefully expand our reiterative corrective actions across additional regions. This work involves re-deploying our targeted fixes to the dependent authentication components to ensure service resilience, while balancing ongoing traffic patterns to avoid additional residual impact. Most users should see recovery across the majority of impacted scenarios, though some scenarios, including those reliant on Graph API and Representational State Transfer (REST) connection methods, will remain degraded until our mitigation efforts are complete. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Wednesday, September 2, 2026, at 3:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: Most users should see recovery across the majority of impacted scenarios, though some scenarios will remain degraded until our mitigation efforts are complete. We're continuing to progress our mitigation efforts across multiple workstreams as we work to restore the service to healthy levels. We understand the challenges incidents such as these have on your organization and we’ll continue to closely monitor service health and prevent further impact. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Wednesday, September 2, 2026, at 1:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: Most users should see recovery across the majority of impacted scenarios, though some scenarios will remain degraded until our mitigation efforts are complete. We're continuing to progress our mitigation efforts across multiple workstreams as we work to restore the service to healthy levels. We understand the challenges incidents such as these have on your organization and we’ll continue to closely monitor service health and prevent further impact. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Wednesday, September 2, 2026, at 1:30 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: We’re continuing to advance multiple workstreams to restore service and prevent additional impact. We’re prioritizing infrastructure that requires the most immediate attention while carefully expanding corrective actions across additional regions, with continued monitoring throughout this process. In parallel, we’re investigating remaining reports of impact and evaluating additional actions to support full service recovery. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 10:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: We are carefully implementing corrective actions while maintaining enhanced monitoring to ensure services remain stable as recovery progresses. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 7:00 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: We've observed continued recovery across previously impacted Exchange Online scenarios, with core mail flow functionality remaining healthy. Our focus remains on validating recovery across dependent Microsoft 365 experiences and confirming that remaining impact scenarios are fully addressed. We're maintaining enhanced monitoring while engineering teams complete end-to-end validation before determining whether any further corrective actions are required. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 6:00 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: Service telemetry continues to indicate recovery across previously impacted scenarios as remediation progresses through the remaining affected infrastructure. Core Exchange Online experiences, including mail flow and search functionality, have recovered. Our focus has shifted toward validating recovery across remaining Microsoft 365 services. We're actively monitoring service health, assessing any residual pockets of impact, and confirming end-to-end functionality across affected workloads. Scope of impact: Users attempting to perform any of the outlined impact scenarios may be affected by this event. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 5:00 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: We're continuing to apply the targeted remediation across the remaining affected infrastructure where needed. Service telemetry continues to show positive recovery trends, with availability improving across previously impacted scenarios. We're actively validating that authentication, connectivity, and search experiences are returning to expected service levels, while maintaining enhanced monitoring to ensure improvements are sustained and any residual impact is addressed. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 4:00 PM UTC

A substantial portion of the remediation deployment has been completed, and organizations whose environments remain affected are expected to recover as the deployment reaches the relevant infrastructure. As remediation progresses, we're focused on validating sustained recovery and monitoring for any remaining pockets of impact before determining whether any additional corrective actions are required. This quick update is designed to give the latest information on this issue. We recognise the impact this issue may be causing for your organization and want to assure you that resolving it remains our highest priority. We appreciate your patience and understanding as we continue working toward mitigation. Next update by: Tuesday, September 1, 2026, at 4:00 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work - Delays or failures when sending or receiving email messages via Outlook for iOS and Android. Current status: We're continuing to apply the targeted authentication component fix across the remaining affected infrastructure where necessary. Service telemetry continues to indicate recovery, with availability increasing across previously impacted scenarios as remediation progresses. We're validating that authentication, connectivity and search operations are returning to expected service levels while monitoring for any residual impact and confirming that the remediation is delivering broad mitigation across affected Exchange Online scenarios. As recovery signals continue to trend positively, we're maintaining extended monitoring across affected service workflows to ensure improvements are sustained. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 4:00 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We're continuing to reapply the targeted authentication component fix to the remaining affected infrastructure where necessary. While our remediation effort is underway, indications from service telemetry remain positive. We're observing an overall increase in service availability, and we're monitoring this closely to ensure we're progressing towards a broad mitigation. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 10:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074.  We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: Reapplying the targeted authentication component fix and restarting affected infrastructure segments has led to measurable progress. We're observing gradual improvements within telemetry data related to search functionality across the remaining affected infrastructure, and we're continuing this remediation effort across additional infrastructure segments while closely monitoring service health telemetry to ensure we're progressing towards a broader recovery. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 9:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: Our efforts to restart affected sections infrastructure and re-apply the targeted authentication component fix has yielded progress, and we're observing incremental improvement reflected in the service health telemetry associated with search functionality across a sample of the affected environment. We're continuing this action for additional sections of infrastructure as we monitor closely to ensure widespread remediation. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 8:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We're continuing our work to restart affected infrastructure and re-apply the targeted authentication component fix to recover search functionality across the affected environments. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 7:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We're persistently reviewing what additional actions may be required to re-apply our targeted authentication component fix and facilitate the recovery of remaining sections of infrastructure correlated with search functionality to ensure the full remediation. Meantime, we've validated persistent recovery for mail flow across the environment and are focusing our work on recovering search functionality. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 6:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We're observing widespread recovery to Exchange Online mail connectivity, though the draining of backlogged mail queues may take longer for some organizations due to the volume of previously queued messages. Our recovery efforts are now focused on re-applying our targeted authentication component fix and restarting certain instances of infrastructure correlated with search functionality to ensure the full restoration of the associated scenarios. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 5:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We're observing residual impact to some downstream scenarios, including search. We're incrementally restarting corresponding instances of infrastructure to ensure our previously applied authentication components are fully saturated, and we're working to identify whether any additional actions are required to achieve resolution. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 4:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We're closely monitoring the health of the service environment amidst our ongoing recovery work, and we're observing some sections of affected infrastructure which aren't accepting the re-applied authentication components as readily as expected. Users can expect to see continued recovery to email delivery, while users may see residual impact to downstream and dependent scenarios, including search, across affected services. We're working to identify whether any additional actions are required to expedite full recovery. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 3:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We’re seeing improvement across the affected environments as we observe the successful albeit gradual implementation of our mitigation actions. Users should expect to see varying degrees of recovery and residual delays until these actions have completed. We're closely monitoring the health of the service environment and will continue to aggressively pursue any available options to expedite our ongoing recovery work, and we'll provide an estimated recovery timeline as soon as one becomes available. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 2:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We're progressively restarting targeted sections of affected infrastructure to ensure the re-applied authentication components are effectively implemented across affected services. We expect this will aid the recovery of affected scenarios. Users should expect delayed delivery of backlogged messages and residual impact across downstream scenarios as these actions are continuing. We'll provide an expected recovery time as soon as one becomes available to us. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 1:00 AM UTC

We're expanding the aforementioned mitigation action more widely across the affected environments as we closely track the recovery of affected scenarios. Users should primarily begin to see gradual recovery to mail flow. Secondarily, and in parallel to the primary mitigation action previously described, we're restarting targeted sections of affected infrastructure to ensure the acceptance of the re-applied authentication components across affected services and aid the recovery of the downstream scenarios. This quick update is designed to give the latest information on this issue. Next update by: Tuesday, September 1, 2026, at 12:00 AM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery work Current status: We're continuing to implement a targeted mitigation to re-apply core authentication components, and we're expanding this action more widely across the affected environments as we closely track the recovery of affected downstream scenarios. Users may notice gradual recovery to the scenarios identified in the "More info" section as our mitigation action takes effect in their corresponding sections of infrastructure, and we're continuing to review whether any additional actions may be required to achieve withstanding recovery across all affected scenarios. We'll provide an estimated time to resolution as soon as one is available. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Tuesday, September 1, 2026, at 12:00 AM UTC

We're implementing a targeted mitigation to re-apply core authentication components across a sample of affected infrastructure and are closely monitoring corresponding service telemetry to validate the efficacy of this action. As a result of this work, some users are beginning to see recovery to some impacted scenarios. We'll continue to incrementally expand this mitigation action more widely across the affected environments as quickly as possible. This quick update is designed to give the latest information on this issue. Next update by: Monday, August 31, 2026, at 11:00 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery workflows. Current status: We're continuing our targeted review of affected infrastructure and recent changes made to the service to definitively confirm the cause of impact. We're additionally continuing to test and implement various mitigation strategies to apply the necessary authentication component, which have so far yielded positive results. We're monitoring these tests and mitigative actions closely and will provide an estimated time to resolution as soon as one is available. We understand the impact that events like these can have for your organization and we appreciate your patience as we work to mitigate this issue with the highest priority. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start Time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Monday, August 31, 2026, at 11:00 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery workflows. Current status: We're reexamining recent changes made to the service to determine why the authentication components aren't being deployed as expected. Additionally, we are exploring every avenue to safely restore the components, including potentially reverting an update the affected infrastructure recently received. We're performing additional tests to evaluate the best course of action moving forward. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start Time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Monday, August 31, 2026, at 10:00 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery workflows. Current status: We're continuing to perform comprehensive tests to ensure our mitigation strategy effectively resolves the issue without introducing additional impact. In parallel, we're exploring alternative remediation avenues to minimize impact in the interim. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start Time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Monday, August 31, 2026, at 8:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: We've confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074. We've opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service. Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery workflows. Current status: We're continuing to fine-tune our remediation strategy as our internal tests progress. We'll aim to provide an estimated time for remediation as soon as it's available. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start Time: Monday, August 31, 2026, at 3:08 PM UTC Preliminary root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact. Next update by: Monday, August 31, 2026, at 8:00 PM UTC

We're continuing to test our remediation strategy and in parallel we're working to confirm whether other services are impacted so we can expand our communications accordingly. This quick update is designed to give the latest information on this issue.

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: Users may experience a variety of symptoms related to this event, including but not limited to: - Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes. - Delays or failures when sending or receiving email messages. - Authentication-related errors when accessing Exchange Online services. - Difficulties accessing or performing actions within Exchange administration experiences. - Intermittent failures affecting mailbox operations and message delivery workflows. Current status: We've identified a potential corrective action for the affected infrastructure and are evaluating deployment options. We're monitoring service telemetry and affected Exchange Online transactions to determine whether the action is reducing impact and to better understand the scope of affected scenarios. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Start Time: Monday, August 31, 2026, at 3:08 PM UTC Next update by: Monday, August 31, 2026, at 6:30 PM UTC

We’ve isolated a common failure pattern across affected Exchange Online requests that is associated with authentication and protocol connectivity. We're analyzing service telemetry to identify the underlying source of impact and validate potential remediation options. Additionally, we’re continuing to assess the scope of impact and monitor for additional affected scenarios. This quick update is designed to give the latest information on this issue. Next update by: Monday, August 31, 2026, at 5:30 PM UTC

Title: Users may be unable to connect to, or experience degraded functionality with Exchange Online User impact: Users may be unable to connect to, or experience degraded functionality with Exchange Online. More info: Users may experience a variety of symptoms related to this event, including but not limited to: Delays or failures when sending or receiving email messages. Authentication-related errors when accessing Exchange Online services. Difficulties accessing or performing actions within Exchange administration experiences. Intermittent failures affecting mailbox operations and message delivery workflows. Current status: We're reviewing service telemetry and diagnostic data to isolate the source of the issue after receiving an increase in user-reported issues affecting Exchange Online. We'll keep refining the 'more info' section as additional impacts are identified. Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. We're continuing our investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available. Next update by: Monday, August 31, 2026, at 5:30 PM UTC

Title: Investigating user reports of Exchange Online issues User impact: We don't have details on impact yet. We're seeing an increase in user reported issues above our alerting threshold. Current status: We are reviewing service telemetry and available information to determine if there is an issue happening and we'll update this message shortly with our latest findings. This communication serves as a preliminary notification about a potential issue affecting your service.