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Offline Outlook OST is in Use and cannot be accessed: Error Resolved

Media Team | Modified: 2016-07-11T05:16:06+00:00 | Error|

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.

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 Application
  • OST file is in use and cannot be accessed. Close any of application that is using this file
  • Default Outlook OST profile is in use thus cannot display the folder & could not be accessed

Reason of Error (OST File is in Use)

  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 sometime interrupts in between & causes the aforementioned error (OST file is in use and cannot be accessed).
  4. The OST file or PST file is in used by application like Microsoft Exchange and all other mail-enabled applications.
  5. Slow Internet Connection may also become a cause of the issue.
  6. In case of unauthorized user or more than one user, accessing the OST file can result in this error.

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

Method1: Change Compatibility Settings

Right click on Lync Shortcut & select properties.

In Compatibility Tab uncheck the checkbox of “Run this program in compatibility mode for

Method2: Reboot Application

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

Method3: Change Privilege

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

Method4: 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, 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 & cannot be accessed)

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 Error:

You can rectify the issue of your corrupt OST file by running ScanOST.exe. The damage issue of OST file can be checked by OST integrity Check Tool. The program 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.

Steps to Run ScanOST.exe:

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


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


    • In case the tool asks for ‘Profile name’ then provide with 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 command: “%LOCALAPPDATA%\Microsoft\Outlook\”
  2. It will showcase you the OST file stored at the location

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