Resolve Outlook PST File Locked By another Process

Bharat BhushanSolution Manager
Experts in data recovery from corrupt Exchange mailboxes, SQL database, and Outlook emails.
Summary: The article lists the effective methods on how to deal with Outlook PST File Locked By another Process error. Read on to learn the important ways to resolve.

An Outlook PST (Personal Storage Table) file is an open proprietary file format that stores local, backed-up copies of your email messages, calendar events, and contacts, among other important items.

A common problem that Windows users have raised concerns over is when the PST file is locked, especially when they’re trying to create backup copies of the files.

The error 0x80070021 pops up when this happens, displaying the message: “The process cannot access the file because another process has locked a portion of the file."

Generally, a PST file locked by another process is the result of a particular add-in installed, an app that depends on the outlook.exe process, or a corrupt Outlook PST file. In this case, Outlook continues to run even when you’ve closed all windows, so if not terminated properly, error 0x80070021 will pop up on your PC.

While this may cause a lot of anxiety and frustration, there are solutions that can resolve the error and help you get back to your work.

How to fix Outlook PST file locked by another process

  1. Use manual methods
  2. Run the Scan PST tool
  3. Use a reliable PST repair software

Use manual methods 

In order to manually fix a PST file locked by another process, you can try the following:

  • Terminate the Outlook app via Task Manager. To do this, press CTRL+SHIFT+ESC. Right click on Outlook.exe and select End Process.
  • Close all apps that are dependent on Outlook
  • Shut down your computer and restart it to force the release of the file lock

If these manual methods do not resolve the problem, try the next solution.

Run the ScanPST.exe tool

Also known as the Inbox Repair tool, the Scanpst.exe tool helps to diagnose and repair problems associated with PST files, like when the PST file is locked.

ScanPST.exe validates and corrects errors in PST file’s internal data structures. If it determines a block as part of an Outlook item, then it removes the same once validated.

To repair an Outlook PST file using the SCANPST tool, take the steps below:

  • Exit Outlook
  • Go to the file location depending on your version of Outlook. If you’re using Outlook 2016, go to Outlook 2016: C:\Program Files (x86)\Microsoft Office\root\Office16
  • Locate the SCANPST.exe file and open it
  • Select Browse to select the PST file you want to be scanned
  • Select Start to begin the scan. By default, a new log file will be created during the scan
  • If errors are found, select Repair to start the fixing process. A backup file will be created during repair.
  • Once the repair is complete, start Outlook using the profile associated with the PST file you have repaired

Use a reliable PST repair software

If you’ve tried the manual methods and the SCANPST.exe tool but you still get error 0x80070021, you can try a reliable PST repair software such as the Stellar Phoenix Outlook PST Repair tool.

This tool scans PST files, repairs, and restores all the contents of your mailbox, then stores the repaired items as a new PST file which you can then import back into Outlook.

How to repair a PST file using Stellar Phoenix Outlook PST Repair

To do this:

  • Run Stellar Phoenix Outlook Repair by double-clicking on its icon
  • Select PST File for Repair, choose the damaged PST file. If you know its location, click Browse; if you don’t, click Find
  • Click on the Repair tab. This will display a preview of emails and other data in the selected PST file for repair
  • Go to the Home menu
  • Click the Save Repaired File icon
  • From the Save Options dialog box, select either PST, EML, MSG, RTF, HTML or PDF file formats
  • Select the Destination Location using the Browse tab

If you can’t open Outlook to import the PST file, do the following:

  • Open Control Panel in your Windows computer
  • Click Mail
  • Select Data Files
  • Find the repaired PST file from the list
  • Select the file and click Set as default
  • Exit and open Outlook to access your recovered mail items

With Stellar Phoenix Outlook Repair software, you can also recover individual mail messages in EML, MSG, RTF, HTML, and PDF format.


Outlook is the standard groupware tool for many organizations that depend on it for email, tasks, contacts, and calendar entries among other items. Files that contain such precious data are fragile so when they are locked, work eventually stops and it can be tedious to fix it.

Fortunately, with tools such as Stellar Phoenix Outlook PST Repair, you can fix even the most severely affected PST file. Whatever size of business you’re in, as long as you depend on Outlook, you may find the need for the services provided by a PST repair tool from Stellar like this one. Have a copy in your software toolbox before the need arises.

Edited by: Andrew Leniart

Bharat BhushanSolution Manager
Experts in data recovery from corrupt Exchange mailboxes, SQL database, and Outlook emails.

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