Offline OST File is in Use and Cannot Be Accessed Outlook: Error Resolved

Written By Andrew Jackson
Anuraag Singh
Approved By Anuraag Singh
Published On October 4th, 2022
Reading Time 5 Minutes Reading

In this blog, we will reveal the best techniques that users can use to fix the “OST file is in use and cannot Be accessed Outlook” error. Here we will discuss the reason for this error and then know how to fix it step by step.

While using Skype or Lync, you can save your conversation into Outlook File. As Lync is a Microsoft product & the features like store IM conversation history, Status: Busy/Free, sync Lync to Exchange Server contacts & share compatibility ratio with Exchange server, etc., make use of your existing OST file.

Error: Lync displays an error message on starting up:  The file c:\User\Admin\AppData\Local\Microsoft\Outlook Data File – my outlook.ost is in use and cannot be accessed. Close any application that is using this file, and then try again. You might need to restart your computer.

OST File is in Use and Cannot Be Accessed Outlook

Instant Solution to Fix This Error: If manual process does not work to fix corruption of OST file, you must use SysTools OST Recovery Tool. This will help the user to repair damaged OST file of Outlook 2019, 2016, 2013, 2010, and all below versions.

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Other Forms of the Error

The aforementioned error appears on several situations with different error format or code. You may face one of these errors.

  • OST file is in use by another utility or application
  • OST file is locked. Try to reboot the Application
  • OST file is in use and cannot be accessed. Close any application that is using this File
  • Default Outlook OST profile is in use thus cannot display the folder & could not be accessed

Reason of OST File is In Use and Cannot Be Accessed Outlook Error

  1. Incompatibility Issue: Due to incompatibility between Lync & Outlook Version, the error is thrown.
  2. Due to Different Folder: In case of two copies of lync.exe, make sure Outlook.exe & Lync.exe run from same directory otherwise you will get an error.
  3. Due to Add-In: Installation of certain Outlook Add-in such as Fax software sometimes interrupts in between & causes the aforementioned error (OST file is in use and cannot be accessed).
  4. Outlook Files used by another program: The OST file or PST file is used by applications like Microsoft Exchange and all other mail-enabled applications.
  5. Due to Unreliable Internet connection: A slow Internet Connection may also become a cause of the issue.
  6. Unauthorized Access: In the case of unauthorized use or more than one user, accessing the OST file can result in this error.

How to Prevent Lync (application) from Locking Outlook .ost File?

Method 1: Change Compatibility Settings

  • Right-click on Lync Shortcut & select properties.
  • In Compatibility Tab uncheck the checkbox “Run this program in compatibility mode for”. Click OK.

Method 2: Reboot The Application

Quit Lync from Task Manager & start Outlook and then try to start Lync. This may avoid the error message of your OST file.

Method 3: Change Privilege

If you have set Lync to Run as Administrator then change the privilege level by unchecking the option.

Method 4: Remove Dependency on OST

Turn off the options in Lync that are accessing the Outlook data. According to the version of Lync or Skype your options may vary. The options like store IM conversation history, Status: Busy/Free, and sync Lync to Exchange Server contacts all make use of your OST file & you need to turn it off if the issue persists & you are unable to process further.

Consequences of The Error OST File is In Use and Cannot Be Accessed Outlook

You can get back to the normal state by shutting down the application or rebooting it but sometimes OST file is severely corrupted after encountering the issue. In addition, it may become difficult to resynchronize the same OST with the Exchange Server.

Rectify Encountered OST file is in Use and Cannot Be Accessed Outlook Issue

You can rectify the issue of your corrupt OST file by running ScanOST.exe. The damage issue of the OST file can be checked by OST integrity Check Tool. The is an inbuilt utility provided by Microsoft that helps in resolving minor cases of OST corruption or you can recover corrupted OST file using third party utility.

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Steps to Run ScanOST.exe:

    • Close the MS Outlook application & check also if it is running in the background.
    • Start ScanOST.exe.


    • If Outlook is running in the background, it will throw an error message:


    • In case the tool asks for ‘Profile name’ then provide the exact name
    • There appear two options: ‘Work Offline’ or ‘Connect’. Click on ‘Connect’
    • Select required option such as ‘Scan all folders‘ etc. as per requirement.
    • Select the ‘Repair Errors’ checkbox to remove any damage issues. Then, click on ‘Begin Scan‘.


Unable to Find OST File?

No issue we will help you find your OST file. Just follow the below instruction:

    1. Click on Start & type “Run


  1. Then type the command: “%LOCALAPPDATA%\Microsoft\Outlook\”
  2. It will showcase to you the OST file stored at the location


In this blog we explained the best ways to OST file is in use and cannot be accessed through Outlook error step-by-step. Here we also learned about the reasons behind this error. If in case you have corrupted the OST file, we also suggested the professional fix it.


By Andrew Jackson

I am SQL DBA and SQL Server blogger too. I like to share about SQL Server and the problems related to it as well as their solution and also I do handle database related user queries, server or database maintenance, database management, etc. I love to share my knowledge with SQL Geeks.