Resolved -
We now consider this incident resolved for the City of Pleasanton.
Microsoft reports that the disruption resulted from a technical issue introduced during an earlier network capacity upgrade, which surfaced after a subsequent network change. Microsoft has stated that the incident was not related to a cyberattack or AI/agents.
Microsoft addressed the underlying issue and gradually restored services, checking stability at each stage to help ensure a reliable recovery. Microsoft will provide a full post-incident report once its review is complete.
If you continue to experience issues with email or other Microsoft 365 services, please submit a service desk ticket through the IT Help Center at [https://help.cityofpleasantonca.gov](https://help.cityofpleasantonca.gov).
Thank you for your patience throughout this disruption.
Nov 14, 15:52 PST
Update -
**Microsoft 365 Outage Update**
Microsoft reports that its systems are stabilizing. You may see improvements when signing in or accessing services, but email delivery may still be delayed as Microsoft works through the backlog of messages and balances traffic across its systems. Being able to open Outlook does not necessarily mean email delivery has returned to normal.
Features in other Microsoft 365 applications that rely on email services may also remain affected. Features that do not rely on those services remain available.
Microsoft has not yet provided an estimated time for full recovery.
Please continue to check our System Status Page for updates. Additional information and our community discussion are available in the [IT Help Center](https://help.cityofpleasantonca.gov) (login required).
Thank you for your continued patience.
Nov 13, 12:21 PST
Monitoring -
Some good news. It looks like most of the services are back online, including most email systems. Microsoft is still reporting issues with some systems, so we will continue to monitor them as they work on getting everything back online.
Nov 13, 09:19 PST
Update -
UPDATE from Microsoft - Thursday, Nov. 12, 2026, 10:17:59 PM
Current status: As part of our ongoing efforts to advance the recoverability of our frontend servers, we’re evaluating traffic controls that can be applied to increase capacity and stability. This includes traffic optimization actions such as traffic throttling, protocol adjustments, and failover routing intended to improve stability in active regions. In parallel, were expanding internal testing to track activity within a contained environment to improve traffic monitoring and issue detection capabilities.
As of now, we are not aware of any malicious activity that is causing this incident. We will continue to treat this incident with urgency and priority until full resolution. Once mitigated, we will provide full details of the root cause, defense-in-depth repair items, and more within a Post-Incident Report.
Note from Pleasanton IT:
Microsoft is still working to restore reliable service. Its teams are adjusting traffic handling to reduce disruptions and improve stability while they investigate the cause. Microsoft has reported no indication of malicious activity at this time.
Services may remain slow or intermittently unavailable until Microsoft resolves the issue. There is no confirmed time for full restoration.
Nov 12, 22:36 PST
Update -
UPDATE from Microsoft - 4:08:53 p.m. PST
Current status: While the servers we've returned to service initially remain healthy, we've observed that they can become unresponsive again once they begin receiving traffic. We're analyzing diagnostic data from these servers with our networking and platform experts to determine what's triggering this behavior.
Building on the protective traffic management measures we've implemented, we're also temporarily limiting which types of traffic can reach the affected infrastructure in specific locations. This will help us determine whether a particular type of request is contributing to the impact and allow us to restore service incrementally. Additionally, we're rebuilding a subset of affected servers using a previous software configuration to validate whether this prevents them from becoming unresponsive, and we'll expand this approach to additional servers if we observe positive results.
Next update by: 5:30 p.m. PST
Nov 12, 16:42 PST
Update -
UPDATE from Microsoft (even more, and more impacted services) - 3:06:31 p.m. PST
Light at the end of the tunnel?
More info: Potentially impacted services include:
- Exchange Online
- Microsoft Teams
- SharePoint Online
- Microsoft Copilot 365
- Microsoft Defender XDR
- Microsoft Planner
- Microsoft To Do
- Microsoft Intune
- Microsoft Defender for Office 365
- Microsoft Purview: Multiple Purview services including Authorization, Auto Labelling, Data Loss Prevention (DLP), Communication Compliance, and Data Classification are impacted.
- Power BI: All users may intermittently be unable to export reports with MIP sensitivity labels to PDF in Power BI.
- Microsoft 365 Apps Admin Center: Multiple services including Cloud Update, Cloud Policy, and Inventory.
- Universal Print: Users may encounter errors submitting print jobs or using admin features.
Current status: We've begun returning a portion of the affected servers to service, and they're remaining stable so far. We’ve also shifted traffic and connections to alternative pathways wherever possible and have observed limited recovery in some regions.
We've streamlined our recovery process to expedite returning the remaining affected servers to service. To further support recovery, we're implementing protective traffic management measures in a specific location to reduce load on the affected infrastructure, and we'll expand these measures to additional locations if we observe positive results. As capacity is restored, users may experience a gradual recovery as their clients reconnect to the service.
To validate a potential recovery approach, we're fully isolating a portion of our service infrastructure, restarting the affected components, and gradually reintroducing traffic to confirm our services remain stable before applying this approach more broadly. We're also analyzing traffic patterns across our entire service infrastructure and evaluating whether isolating traffic within each region may allow affected regions to recover independently.
Next update by: 4:30 p.m. PST
Nov 12, 15:13 PST
Update -
UPDATE from Microsoft (even more impacted services) - at 2:11:39 p.m. PST
More info: Potentially impacted services include:
- Exchange Online
- Microsoft Teams
- SharePoint Online
- Microsoft Copilot 365
- Microsoft Defender XDR
- Microsoft Planner
- Microsoft To Do
- Microsoft Intune
- Microsoft Defender for Office 365
- Microsoft Purview: Multiple Purview services including Authorization, Auto Labelling, Data Loss Prevention (DLP), Communication Compliance, and Data Classification are impacted.
- Power BI: All users may intermittently be unable to export reports with MIP sensitivity labels to PDF in Power BI.
- Microsoft 365 Apps Admin Center: Multiple services including Cloud Update, Cloud Policy, and Inventory.
Current status: We’re continuing to pursue all available pathways to restore service, as our actions taken thus far have not provided the anticipated relief. Our investigation has found that a core process on the affected servers is becoming overwhelmed, which causes the servers to stop responding and contributes to the capacity loss.
To validate a potential recovery approach, we're fully isolating a portion of our service infrastructure, restarting the affected components, and gradually reintroducing traffic to confirm our services remain stable before applying this approach more broadly. We're also analyzing traffic patterns across our entire service infrastructure and evaluating whether isolating traffic within each region may allow affected regions to recover independently.
Previous status: We're continuing to work through restarting and validating the affected servers to safely return them to service, and we're exploring opportunities to expedite this process. In parallel, we're assessing whether reverting the small number of recent configuration updates we identified could help accelerate recovery.
Scope of impact: This issue may affect users attempting to access the affected Microsoft 365 services.
Next update by: 3:30 p.m. PST
Nov 12, 14:30 PST
Update -
UPDATE (which is not much of an update - but added more impacted services) from Microsoft - at 12:44:51 p.m. PST
More info: Potentially impacted services include:
- Exchange Online
- Microsoft Teams (Pleasanton IT Note: MS Teams seems to be functional for our org)
- SharePoint Online
- Microsoft Copilot 365
- Microsoft Defender XDR
- Microsoft Planner
- Microsoft To Do
Current status: While validating the targeted change, we found that many of the affected servers have become unresponsive, which is preventing us from confirming whether the change is effective. We're restarting these servers so they can come back online with the change in place, and we're applying the same approach to additional affected portions of our infrastructure to validate the results more broadly.
Previous Status: While we haven't identified any recent changes that correlate with the start of impact, our investigation indicates the failed health checks may originate from a specific component on the affected servers that's responsible for processing them. We're deploying a targeted change to bypass this component on a subset of servers to validate whether this restores availability, and we've taken steps to prevent additional servers from being removed from service while we work to return the affected servers to service. We're also investigating why affected servers are experiencing elevated processor usage while handling requests.
Scope of impact: This issue may affect users attempting to access the affected Microsoft 365 services.
Next Update: 1:30 p.m. PST
Nov 12, 12:50 PST
Update -
Microsoft 365 Outage: Additional Information and Community Discussion
In addition to our System Status Page, you can find more information in the IT Help Center: https://help.cityofpleasantonca.gov. Login is required.
We’ve also opened a Microsoft 365 Outage community discussion: https://help.cityofpleasantonca.gov/hc/en-us/community/posts/50350406796685-Microsoft-365-Outage-Nov-12-Where-to-Check-for-Updates where you can ask questions, share what’s working for you, or offer assistance to colleagues on matters that don’t necessarily require a service desk ticket. You’ll also find the discussion linked on the Help Center home page, directly below the red Microsoft 365 outage notice.
Please continue to use the System Status Page for service updates and submit a service desk ticket if you need individual IT assistance.
Thank you for your patience and for helping one another.
Nov 12, 11:44 PST
Update -
UPDATE from Microsoft - at 11:16:03 a.m. PST
Current status: We're aggressively pursuing all pathways to reduce impact. As a precaution, we've paused all deployments and configuration changes while we review recent changes for any correlation to this event. We've also moved traffic for some services off the affected infrastructure to further reduce load, with additional traffic moves in progress.
Scope of impact: This issue may affect users attempting to access the affected Microsoft 365 services.
Nov 12, 11:31 PST
Update -
UPDATE from Microsoft - at 10:59:24 a.m. PST
User impact: Users may be unable to connect to multiple Microsoft 365 services.
More info: Potentially impacted services include:
- Exchange Online
- Microsoft Teams
- SharePoint Online
- Microsoft Copilot 365
- Microsoft Defender XDR
Current status: We've completed redistributing connection traffic across our worldwide infrastructure, and we're moving additional traffic off the affected infrastructure to further reduce load. We're also restarting affected servers to return them to service. In parallel, we're investigating whether the elevated traffic reflects a genuine increase in requests or a shift in how traffic is being routed across our infrastructure.
Scope of impact: This issue may affect users attempting to access the affected Microsoft 365 services.
Next Update from Microsoft: expected by 1:00 p.m. PST today
Nov 12, 11:12 PST
Update -
From Microsoft: We're investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas.
From Pleasanton IT: Impacts have been on our email services, Admin Console, and other hosted Microsoft services; MS Teams appears to be up, however.
Nov 12, 10:48 PST
Investigating -
Many users are reporting trouble accessing Outlook on the web or delays receiving email. The issue appears widespread across our organization. We’re investigating whether it’s related to a Microsoft service disruption and will share updates as more information becomes available.
Nov 12, 10:27 PST
