Zix - M365 - Some users may be unable to connect to Microsoft 365 Exchange Online
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OpenText experienced a major incident: Zix - M365 - Some users may be unable to connect to Microsoft 365 Exchange Online. ServiceAlert observed recovery on Sep 4, 2026.
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Incident Lifecycle
Affected Components
Zix Office 365
Incident Timeline
Monitoring
Update from Microsoft:
All user impact scenarios are now resolved as they rectified the additional mitigation efforts for the Outlook impact which occurred in less than one percent of their infrastructure. They will continue to monitor their telemetry to ensure all services remain healthy and plan to close this communication by next update.
All user impact scenarios are now resolved as they rectified the additional mitigation efforts for the Outlook impact which occurred in less than one percent of their infrastructure. They will continue to monitor their telemetry to ensure all services remain healthy and plan to close this communication by next update.
Sep 3, 2026 at 6:33 PM UTC
Monitoring
Update from Microsoft:
Microsoft discovered an issue in less than one percent of their infrastructure, where 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. Microsoft remains committed to restoring all services to all users and will continue to carefully moni...
Microsoft discovered an issue in less than one percent of their infrastructure, where 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. Microsoft remains committed to restoring all services to all users and will continue to carefully moni...
Sep 3, 2026 at 4:45 PM UTC
Monitoring
Update from Microsoft:
Their telemetry indicates service availability remains stable above 99 percent and expect the majority of users should no longer be seeing impact from this issue. The continued focus is on balancing the implementation of their 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.
Their telemetry indicates service availability remains stable above 99 percent and expect the majority of users should no longer be seeing impact from this issue. The continued focus is on balancing the implementation of their 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.
Sep 2, 2026 at 12:18 PM UTC
Monitoring
Update from Microsoft:
Microsoft continues to advance multiple workstreams to restore service and prevent additional impact. Microsoft is prioritizing infrastructure that requires the most immediate attention while carefully expanding corrective actions across additional regions, with continued monitoring throughout this process. In parallel, Microsoft is investigating remaining reports of impact and evaluating additional actions to support full service recovery.
Microsoft continues to advance multiple workstreams to restore service and prevent additional impact. Microsoft is prioritizing infrastructure that requires the most immediate attention while carefully expanding corrective actions across additional regions, with continued monitoring throughout this process. In parallel, Microsoft is investigating remaining reports of impact and evaluating additional actions to support full service recovery.
Sep 1, 2026 at 9:57 PM UTC
Monitoring
Update from Microsoft:
Microsoft observed continued recovery across previously impacted Exchange Online scenarios, with core mail flow functionality remaining healthy. Their focus remains on validating recovery across dependent Microsoft 365 experiences and confirming that remaining impact scenarios are fully addressed. They are maintaining enhanced monitoring while engineering teams complete end-to-end validation before determining whether any further corrective actions are required.
Microsoft observed continued recovery across previously impacted Exchange Online scenarios, with core mail flow functionality remaining healthy. Their focus remains on validating recovery across dependent Microsoft 365 experiences and confirming that remaining impact scenarios are fully addressed. They are maintaining enhanced monitoring while engineering teams complete end-to-end validation before determining whether any further corrective actions are required.
Sep 1, 2026 at 5:07 PM UTC
Identified
Update from Microsoft:
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, Microsoft is focused on validating sustained recovery and monitoring for any remaining pockets of impact before determining whether any additional corrective actions are required.
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, Microsoft is focused on validating sustained recovery and monitoring for any remaining pockets of impact before determining whether any additional corrective actions are required.
Sep 1, 2026 at 12:26 PM UTC
Investigating
Update from Microsoft:
Microsoft is continuing to perform comprehensive tests to ensure their mitigation strategy effectively resolves the issue without introducing additional impact. In parallel, they are exploring alternative remediation avenues to minimize impact in the interim.
Microsoft is continuing to perform comprehensive tests to ensure their mitigation strategy effectively resolves the issue without introducing additional impact. In parallel, they are exploring alternative remediation avenues to minimize impact in the interim.
Aug 31, 2026 at 8:14 PM UTC
Investigating
Update from Microsoft:
Microsoft has identified a potential corrective action for the affected infrastructure and are evaluating deployment options. They are 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.
Microsoft has identified a potential corrective action for the affected infrastructure and are evaluating deployment options. They are 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.
Aug 31, 2026 at 5:51 PM UTC
Investigating
Update from Microsoft:
Microsoft isolated a common failure pattern across affected Exchange Online requests that is associated with authentication and protocol connectivity. They are analyzing service telemetry to identify the underlying source of impact and validate potential remediation options. Additionally, they are continuing to assess the scope of impact and monitor for additional affected scenarios.
More info - Users may experience a variety of symptoms related to this event, includi...
Microsoft isolated a common failure pattern across affected Exchange Online requests that is associated with authentication and protocol connectivity. They are analyzing service telemetry to identify the underlying source of impact and validate potential remediation options. Additionally, they are continuing to assess the scope of impact and monitor for additional affected scenarios.
More info - Users may experience a variety of symptoms related to this event, includi...
Aug 31, 2026 at 4:57 PM UTC
Investigating
Microsoft O365 Exchange - some users are experiencing an issue connecting to Exchange 365. Microsoft is aware of the issue and has provided Issue ID: EX1464935.
Aug 31, 2026 at 4:33 PM UTC
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