New issue on bcdr

Author: kaushika-msft

support/windows-365/toc.yml

@@ -67,3 +67,7 @@ items:
     items:
     - name: Windows 365 Switch known issues
       href: windows-365-switch-known-issues.md
+  - name: Windows 365 BCDR
+    items:
+    - name: Windows 365 BCDR known issues
+      href: windows-365-bcdr-known-issues.md      

support/windows-365/troubleshoot-windows-365-bcdr-known-isssues.md

@@ -0,0 +1,29 @@
+title: Windows 365 BCDR known issues
+description: This article provides troubleshooting steps for the recent known issues with Windows 365 disaster recovery
+author: kaushika-msft
+ms.author: kaushika
+ms.reviewer: kaushika; aradinger
+ms.date: 10/16/2025
+ms.topic: troubleshooting-known-issue
+ms.service: windows-365
+ms.custom: pcy:WinComm User Experience
+---
+# Windows 365 BCDR known issues
+
+## Summary
+
+This article addresses a known issue related to Windows 365 Business Continuity and Disaster Recovery (BCDR) scenarios.
+
+## classic Outlook corruption after disaster recovery failback and failover
+
+This issue occurs when the Outlook offline cache becomes corrupted after restoring a Cloud PC from a snapshot during a disaster recovery failover or upon failing back to the primary region post-disaster. Users may encounter an error message when starting Outlook.
+
+The root cause lies in the synchronization process between the client and server. During a failover, the client and server become out of sync because the client on the snapshot reflects a past state relative to the server's current status. Although no data is lost, the process of re-synchronizing the Offline Storage Table (OST) file can take time.
+
+### Solution
+
+To resolve this issue, follow these steps:
+1. **Short-term solution**:Delete the OST file on the Cloud PC after completing a failover or failback. This action forces Outlook to rebuild the offline cache of the mailbox, along with the search index. No user data will be lost during this process.
+2. **Long-term solution**:Switch to the new Outlook app. The new Outlook app uses a different caching mechanism that eliminates this synchronization issue.
+
+By applying these troubleshooting measures, you can address the issue and ensure smoother operation of Outlook in disaster recovery scenarios.