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Fix Outlook PST Sync Errors with OneDrive – Updated 2026 Guide

Ritu Roy | how to mac os outlook outlook error PST software | 5 minutes read | Modified on: 28-01-2026

You can fix the issue of Outlook PST Sync Errors with OneDrive by using a few practical solutions, such as closing Outlook, relocating PST files outside the OneDrive folder, or repairing damaged data files. This article walks you through effective methods that can help resolve the problem quickly and restore normal synchronization.

Why Does Outlook PST Fail to Sync with OneDrive?

When Outlook is configured using a POP3 account, it stores all mailbox information in a PST (Personal Storage Table) file. This data file is continuously accessed and updated while Outlook is active. As a result, Outlook keeps the PST file in use, preventing other applications from accessing it simultaneously.

When OneDrive attempts to synchronize the same PST file while Outlook is running, it may be unable to access the file. This conflict often leads to syncing errors or incomplete uploads.

In some cases, synchronization problems may also appear after installing recent Windows or Outlook updates. For instance, several users experienced PST-related issues following certain Windows 11 updates. In such scenarios, Microsoft has suggested removing the PST file from the OneDrive directory and, if necessary, rolling back or uninstalling the problematic update to restore normal functionality.

Common Reasons Outlook PST Fails to Sync with OneDrive

Before applying any fixes, it’s important to understand what might be causing the synchronization problem. Below are some common factors that can interrupt the syncing process:

When Outlook is running, the PST file often remains in active use, preventing OneDrive from accessing it for synchronization.

If the same PST file is being edited or updated across multiple systems at the same time, OneDrive may encounter conflicts that stop the sync.

OneDrive’s built-in syncing limitations or policy restrictions can also interfere with large or frequently updated PST files.

In some situations, the PST file may continue running in the background even after Outlook has been closed, keeping it inaccessible.

Other background applications or services might be accessing the PST file, which can block OneDrive from syncing it properly.

Corruption within the PST file itself can cause sync failures or repeated errors during the upload process.

Insufficient OneDrive storage space or exceeding assigned quota limits can also prevent PST files from syncing successfully.

What Are the Solutions to Fix Outlook Not Syncing with OneDrive?

If Outlook data is failing to synchronize with OneDrive, try the methods below to resolve the issue effectively.

Method 1: Exit Outlook and End Related Background Tasks

When Outlook is active, the PST file remains in use and becomes inaccessible to other applications. Since OneDrive needs access to the file to upload it, this can lead to synchronization failures. To avoid this conflict, ensure Outlook and all related background services are completely closed.

Follow these steps:

#1: Press Ctrl + Shift + Esc together to open the Task Manager.

#2: Navigate to the Processes section.

#3: Look for any entries related to Outlook, such as Microsoft Outlook or Outlook.exe.

#4: Right-click each identified process and select End Task.

#5: If prompted, confirm your action to terminate the process.

Repeat the steps for all Outlook-related entries. Once everything is closed, check whether OneDrive is able to sync the PST file. If the problem continues, proceed to the next solution.

Method 2: Relocate PST File Using a Symbolic Link

When a PST file is stored in OneDrive, both Outlook and OneDrive attempt to access it at the same time. Outlook locks the file while reading or writing emails, which prevents OneDrive from syncing it properly. Creating a symbolic link allows you to move the PST file to a local folder while making Outlook think it’s still in OneDrive. Essentially, the symbolic link acts as a pointer in the OneDrive folder that redirects Outlook to the file’s new location on your system. This approach reduces conflicts during synchronization.

Steps to Set Up a Symbolic Link:

  1. Close the Outlook application completely.
  2. Create a new folder on your local drive, for example: C:\OutlookPST\.
  3. Move your PST file from the OneDrive folder into the newly created local folder.
  4. Open the Command Prompt as an administrator.
  5. Run the following command (adjust paths according to your setup):

mklink “C:\Users\username\Documents\Outlook Files\TestFile_01.pst” “D:\New PST Location\TestFile_01.pst”

  • After executing the command, a .symlink file will appear in the original OneDrive folder.
  • Launch Outlook and continue using it as usual; the application will now access the PST file via the symbolic link without causing sync issues.

Method 3: Repair a Corrupted PST File

Sometimes PST files may be damaged, which can prevent OneDrive from syncing them. You can fix minor corruption using ScanPST.exe, an inbuilt utility in Outlook.

Steps to Repair PST Files Using ScanPST:

  • Locate ScanPST.exe
  • This utility is installed in the Outlook program folder. The exact path may vary depending on your Outlook version.

Run the Utility

  • Navigate to the ScanPST.exe location and double-click to launch it.
  • Click the Browse button, find your PST file, and select it.
  • Press Start to begin scanning.

Repair the File

  • If errors are detected, ScanPST will display a message: “Errors were found in the file.”
  • Click Repair.
  • Optionally, make a backup of the scanned file before repairing.
  • Press OK to begin the repair process.
  • Once finished, you’ll see the “Repair Complete” message.

ScanPST works well for minor corruption, but it may fail or crash if the PST file is very large or severely damaged. In such cases, you can use MacArmy PST Converter for Mac. While it cannot repair the file directly, it safely extracts the data and converts the PST into more than 15 different formats, including PDF, MBOX, EML, OLM, HTML, CSV, DOC, TXT, Yahoo Mail, Gmail, Office365, and more.

The software is designed with a simple interface, making it easy for both beginners and advanced users. Its versatile features allow you to export or back up PST data according to your requirements, ensuring your emails remain accessible even if the original PST is corrupted.

Steps to Convert PST Files for Backup

You can safeguard your Outlook data by transforming PST files using a reliable Mac application. Follow these steps to perform the process easily:

  1. Install the software on your macOS device and open it.
  2. Click Add File(s) or Add Folder to select the PST files you want to back up.
  3. Check that all required PST files appear in the list, then click Next to continue.
  4. Choose the desired export type and click Next to proceed.
  5. Configure any additional settings according to your requirements, then press Export to start the conversion.
  6. Track the transformation process in real time using the Live Conversion Report.

Note: To explore the full functionality, you can download the free demo version, which allows you to convert up to 25 PST files at no cost.

Conclusion

In this guide, we discussed multiple ways to resolve the “Outlook PST Not Syncing with OneDrive” issue. You can choose the method that best suits your needs and perform the task without complications.

Before starting any repair or conversion process, it’s strongly recommended to create a backup of your PST files to prevent accidental data loss. For additional support or questions, you can reach out to MacArmy Support for assistance.