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:
- 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

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

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

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

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

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.