Outlook PST File on OneDrive Causes Sync Error: How to Move Off

If you store an Outlook PST data file in OneDrive, you may see sync errors, file corruption warnings, or Outlook failing to open. OneDrive constantly syncs the PST file to the cloud, and because Outlook locks the file during use, the sync fails and produces errors like “We can’t sync this file” or “Something went wrong.” This article explains why PST files and OneDrive do not mix and provides a step-by-step method to move the PST file to a local folder where Outlook and Windows can manage it without interference.

Why PST Files in OneDrive Cause Sync Errors

Outlook PST files are single-user data files that contain your emails, calendar items, contacts, and tasks. When Outlook is open, it locks the PST file exclusively so that no other process can write to it. OneDrive, however, tries to upload any changed file in its monitored folder to the cloud. Every time Outlook writes a new email or modifies a folder, OneDrive attempts to sync the PST file, fails because the file is locked, and logs a sync error.

Over time, repeated failed sync attempts can corrupt the PST file. OneDrive may also create conflict copies named “filename (yourname’s conflicted copy).pst” which further confuse Outlook. The Microsoft 365 support documentation explicitly states that PST files should not be stored on network drives, cloud storage folders, or external USB drives because Outlook requires direct, exclusive read-write access to the file at all times.

OneDrive Sync Engine Behavior

The OneDrive sync engine uses a file watcher that triggers an upload whenever a file is modified. For a PST file that Outlook modifies every few seconds, the watcher constantly queues upload attempts. Each attempt fails with a file-in-use error, causing the OneDrive icon in the system tray to show a red X or a warning badge. The sync error log in OneDrive Settings > Backup > Manage Backup shows entries like “This file can’t be synced” for the PST file.

Risk of PST File Corruption

A PST file that is partially written when OneDrive tries to sync can become inconsistent. If you close Outlook while a sync is in progress, the PST file may be left in a state that the Inbox Repair Tool (Scanpst.exe) cannot fully recover. The only reliable prevention is to keep the PST file outside any cloud sync folder.

Steps to Move the PST File Out of OneDrive

Before moving the file, close Outlook completely. Then follow these steps to relocate the PST file and reconnect it in Outlook.

1. Close Outlook
   Click File > Exit in Outlook or right-click the Outlook icon in the system tray and select Exit. Confirm that no Outlook process is running by opening Task Manager with Ctrl+Shift+Escape and checking that Outlook.exe is not listed under Processes.
2. Open Account Settings in Outlook
   Launch Outlook. Go to File > Account Settings > Account Settings. In the dialog that opens, click the Data Files tab. This lists every PST file attached to your current Outlook profile along with its full folder path.
3. Identify the PST file in OneDrive
   Select the PST file entry that shows a path containing “OneDrive” in the location column. Click the Open File Location button. Windows File Explorer opens and highlights the PST file. Note the exact folder path for later verification.
4. Create a local folder for PST files
   In File Explorer, navigate to C:\Users\YourUsername\Documents. Create a new folder named Outlook Files. Alternatively, create C:\Outlook Files at the root of drive C. This folder will store the PST file permanently.
5. Close Outlook again and copy the PST file
   Close Outlook. Right-click the PST file in the OneDrive folder and select Copy. Navigate to the new local folder you created and press Ctrl+V to paste the file. Do not cut or delete the original yet.
6. Remove the PST file from Outlook
   Open Outlook. Go to File > Account Settings > Account Settings > Data Files. Select the PST entry that points to the OneDrive location and click Remove. Confirm the removal when prompted. The data stays in the PST file; only the reference in Outlook is removed.
7. Add the copied PST file to Outlook
   In the same Data Files tab, click Add. Browse to the new local folder, select the PST file you copied, and click OK. Outlook mounts the PST file and displays it in the folder pane under the name you gave it.
8. Delete the original PST file from OneDrive
   After confirming that Outlook shows all your data correctly, navigate to the original OneDrive folder and delete the PST file. Empty the Recycle Bin to ensure OneDrive no longer tracks the file. OneDrive will stop showing sync errors for that file.

If Outlook Still Has Issues After Moving the PST File

After moving the PST file, some problems may persist. Below are common scenarios and how to resolve them.

Outlook Shows “The file path is invalid” After Moving

This error appears if you used the Move button inside Outlook instead of manually copying the file. The Move button in Outlook only works within the same logical drive. Always use the copy-and-remove method described above. If you see this error, remove the broken PST reference in Data Files and add the PST file from its new location.

OneDrive Still Shows the PST File in Sync Errors

If OneDrive still reports sync errors for the PST file, check whether a copy remains in the OneDrive folder. Search your OneDrive folder for any file ending in .pst. Delete all PST files from OneDrive. Also check the OneDrive recycle bin online at onedrive.live.com and permanently delete any PST files there.

Outlook Cannot Find the PST File After a PC Restart

This happens if you placed the PST file on a drive that is not always available, such as a removable drive or a network share. Move the PST file to C:\Users\YourUsername\Documents\Outlook Files, which is always available on the local system drive. After moving, remove and re-add the PST file in Outlook.

Local PST Storage vs OneDrive PST Storage: Key Differences

Item	Local PST Storage	OneDrive PST Storage
Sync behavior	No sync; file is accessed directly by Outlook	OneDrive attempts continuous sync, fails due to file lock
File corruption risk	Low, because no external process touches the file	High, due to partial writes during sync attempts
Error messages	None from OneDrive	“We can’t sync this file,” red X on OneDrive icon
Data accessibility	Only on the local PC where PST resides	Attempts to sync to cloud but fails; no remote access
Backup method	Manual copy to external drive or manual upload to cloud	OneDrive cannot back up a locked PST file

After moving your PST file to a local folder, OneDrive sync errors will stop immediately. You can now open and close Outlook without seeing warning icons in the system tray. As a next step, set up a regular manual backup of the PST file by copying it to an external hard drive or a separate cloud folder while Outlook is closed. For advanced users, consider converting the PST file to a Microsoft 365 Group mailbox or an Exchange Online mailbox to avoid PST files entirely.