1. Exchange Online: Temporary Mailbox Access Disruption via MAPI
Overview
Some Exchange Online users experienced mailbox access issues via the Messaging API (MAPI) on August 20, 2025. The disruption occurred after Microsoft reverted a recent service change. This triggered MAPI service restarts across multiple regions as the incident began at 7:00 PM UTC, got resolved by 8:54 PM UTC the same day. So, Microsoft has now confirmed that the service health has fully been restored. Microsoft are still continuing to monitor stability.
Impact
Users in North America were primarily affected, with some in Canada, South America, Europe, etc, also experiencing difficulty accessing their mailboxes via MAPI. The outage lasted nearly two hours. It was linked directly to service restarts during the change rollback process.
Action Needed
No customer action required!! Service has returned to normal and Microsoft is reviewing its change reversion processes to prevent similar incidents in future.
2. Windows Reset and Recovery Issue Fixed with Out-of-Band Update
Overview
Microsoft released an out-of-band (OOB) cumulative update on August 19, 2025, to resolve failures in reset/recovery operations on some Windows devices. The issue appeared after installing the August 2025 Windows security update on specific client versions of Windows. The new OOB update replaces all prior updates for affected versions.
Impact
Devices running Windows 11 (23H2, 22H2), Windows 10 (22H2), and Windows 10 LTSC (2021 and 2019, including IoT Enterprise) could experience failed reset or recovery attempts if only the August 2025 security update was applied. Systems not impacted by this issue do not require the OOB update.
Action Needed
If your devices are affected, install the relevant OOB update instead of the August 2025 security update:
- Windows 11 (23H2, 22H2): KB5066189 (OS Builds 22621.5771, 22631.5771)
- Windows 10 (22H2): KB5066188 (OS Builds 19044.6218, 19045.6218)
- Windows 10 Enterprise LTSC 2021 / IoT LTSC 2021: KB5066188 (OS Builds 19044.6218, 19045.6218)
- Windows 10 Enterprise LTSC 2019 / IoT LTSC 2019: KB5066187 (OS Build 17763.7683)
If the August 2025 security update has not yet been installed, apply this OOB update directly. No further action needed for unaffected devices!!
3. Streamlined File Preview and Copilot Chat in Microsoft 365 Copilot iOS App
Overview
The Microsoft 365 Copilot app for iPhone is shifting to a new file preview experience for Word, Excel, PowerPoint, and other apps on September 15, 2025. Users will now be able to view file contents, comments, etc and interact with Copilot Chat for insights or commands.
Editing will no longer be available in the Copilot app; instead, users will be prompted to open/install the standalone Word, Excel, or PowerPoint apps. The same experience will roll out to iPad devices shortly after.
Impact
- From August 22, 2025, iOS users have begun seeing banners in the Copilot app encouraging installation of Word, Excel, PowerPoint apps, etc.
- From September 15, 2025, iPhone users will only be able to preview files and use Copilot Chat in the Copilot app. Editing must be done in standalone apps.
- Teams, OneDrive, and Outlook will stop opening these files for editing in Copilot, instead redirecting users to standalone apps.
- The “Create” option in Copilot will move to a chat-first workflow. Here, new files are generated through prompts and then can be opened in standalone apps for editing.
- After September 15, similar updates will be applied to the iPad app.
Action Needed
No admin action required!!
However, organizations should:
- Inform iOS users about the new experience, recommend installing Word, Excel, and PowerPoint apps.
- Update internal documentation and training to reflect the change.
For MDM-managed environments, consider pushing standalone Word, Excel, PowerPoint, and OneDrive apps to iOS devices.
4. Enforcement of Admin Settings in Microsoft Fabric Public API and CI/CD
Overview
Microsoft Fabric is enforcing tenant and capacity-level admin settings that restrict the creation of Fabric items, Starting September 15, 2025. This enforcement applies to all creation methods i.e. Git integration, Deployment pipelines, the Fabric Create Item public API, etc. The change ensures that admin-defined restrictions are consistently applied.
Impact
- New item creation: If admin settings block certain Fabric item types (whether in Preview or GA), those items can no longer be created by any method.
- Existing items: Items created before enforcement remain unaffected. They won’t be deleted.
- Creation methods affected:
- UPDATE action in Git integration
- Initial deployment of items in Deployment pipelines
- Fabric Create Item public API
Action Needed
Admins should review tenant and capacity-level Fabric item creation settings. They need to confirm they reflect organizational policies. Update settings if needed.
5. Outlook for Windows: Temporary Access Issue with New Desktop Client
Overview
Some users were unable to open the new Outlook desktop client on Windows devices between August 18–19, 2025. Microsoft confirmed the issue was linked to a recent deployment and has since reverted services to the last stable build. Service has been fully restored.
Impact
- About 5% of users opening the new Outlook desktop client on Windows may have been affected.
- The issue started on August 18, 2025, and was resolved on August 19, 2025, at 5:17 PM UTC.
- Users could still access mail by switching to the Outlook classic desktop client as a workaround.
- The problem was caused by a deployment aimed at service optimization, which triggered unexpected crashes.
Action Needed
No action required from users or admins!! Microsoft has reverted the faulty updates as well.
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