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“It was working on a critical project due in the morning. Suddenly, my Outlook displayed a message- my OST file was inaccessible because it was currently in use by another program.

I had been working on that OST file for days, and now I have to start from scratch. This couldn’t be happening! Frantically, I searched for solutions. Most of the advice involved complicated steps that required technical expertise. But then I found some easy solutions.

I followed the instructions, and within minutes my OST file was back where it belonged and was accessible on my Outlook. With a few clicks of the mouse, I resumed work on my project- just in time to finish and submit before the deadline.”

If you are also experiencing this issue, don’t worry. You can fix it by going through the instructions in this post. We have also provided an automated solution as an added bonus that will help you resolve the issue in minutes. So, without further ado, let’s get started.

Reasons for the “OST file is in Use and Cannot be Accessed” Issue

The problem “OST file is in use and cannot be accessed” is a very common error that usually occurs when the user is trying to access their Outlook data file. There are a few basic reasons why this error might occur:

  • The Outlook data file might be open in another program or process.
  • The file might be open in read-only mode.
  • There are permissions issues with the file.
  • More than one user accessing the same OST file
  • OST file accessed without authorization
  • Slow or unreliable internet connection
  • The file might be corrupted due to a virus attack or some other reason
Methods to fix the “OST file is in use and cannot be accessed” issue
Method 1: Disable Cached Exchange Mode

This error can prevail due to a wide range of factors, but one general cause is that your Exchange Server is configured for Cached mode and your Outlook client is not. This can happen if you have just moved to a new computer or upgraded your Outlook version. Here, we will show you how to disable Exchange cached mode to fix the error.

  • Click on the File tab in MS Outlook.
  • Click on Account Settings, and then click on Account Settings again.Account Settings
  • Select the Exchange account, and then click Change.
  • Uncheck the box next to the option “Use Cached Exchange Mode,” and then click Next.Use Cached Exchange Mode
  • Click Finish, and then click Close.
  • Exit and restart Microsoft Outlook for the changes to take effect.
Method 2: End MS Outlook Processes

In case you are getting the “OST file is in use and cannot be accessed” message, it means that a process that is using the OST file needs to be closed. Here are the steps to close MS Outlook and related processes so that you can fix the error.

  • Access the Task Manager by pressing Ctrl+Alt+Delete.
  • Click on the Processes tab.
  • Find all instances of outlook.exe or msimn.exe and select End Process for each one.End Process
  • Close Task Manager and try to access your OST file again.
Method 3: Recreate OST File

Below are four easy steps to recreate OST file and fix the error.

  • Exit all applications that are using Outlook data files. This error message appears when an application is trying to access an Outlook data file that is already in use.
  • After exiting all applications, reboot your computer. This will ensure that all applications are truly closed and no longer have any access to the Outlook data file.
  • The next step is to delete the .ost file. To do this, simply navigate to the location of the file on your computer and delete it.
  • The final step is to restart Outlook. Once Outlook has been restarted, a new .ost file will be created & the error message should no longer appear.
Method 4: Disable the Outlook Add-ins

If you receive the error pop-up “OST file is in use and cannot be accessed” when trying to open Outlook, it may be due to a corrupted or outdated add-in. Here, we’ll give you a few steps on how to disable trouble some Outlook add-ins so you can get your email up and running again.

  • Access outlook and go to File > Options > Add-Ins.
  • In the Add-Ins dialog box, select COM Add-Ins from the Manage drop-down at the bottom of the screen & then click Go.
  • In the COM Add-Ins dialog box, deselect any add-ins that are checked and then click OK.COM Add-Ins dialog box
  • Close Outlook and then launch it again normally. This time, you should not receive the error message.
Method 5: OST to PST Conversion (Manual and Automated)

Sometimes the OST file gets damaged or corrupted due to various reasons such as power failure, abrupt system shutdown, virus attack, etc. In such cases, you just need to convert the OST file to PST (Personal Storage Table) format so that you can access the data.

There are two methods that you can use to convert the OST file to the PST format: Manual and Automated. Let’s have a look at both methods:

  1. Manual Method: Use Microsoft’s inbuilt ‘Export’ feature
    • First of all, open MS Outlook & go to the ‘File‘ option.
    • Then click on ‘Open & Export‘ and select ‘Import/Export.’Import/Export
    • A new window will open. Here, select the option ‘Export to a file‘ and tap on ‘Next.’Export to a file
    • Now choose ‘Outlook Data File (.pst)’ & click on ‘Next‘.
    • Select the folder that you wish to export & tap ‘Next.’
    • Now browse the location where you intend to save the converted PST file and click on ‘Finish‘.
  2. Automated Method: Use OST to PST Converter

    Kernel for OST to PST Converter is a professional tool that allows you to convert an Offline Storage Table (OST) file into Personal Storage Table (PST) format within a few minutes. This tool also provides various features such as the recovery of deleted or permanently deleted items from an OST file, repair corrupt OST files and recover emails, recovery of password-protected OST files, conversion of encrypted OST files, etc. Moreover, it is compatible with all versions of MS Outlook, including 2021 and Exchange Server 2019.

    Follow the steps given below to convert an OST file into PST format:

    1. First of all, download and install the tool on your system.
    2. Then launch the tool. Browse the location of your corrupt or damaged OST file and click on the ‘Next‘ button.Browse the location
    3. The tool will now scan your selected OST file and display all recoverable items in a tree-like structure.
    4. You can preview each item before saving them into desired output formats such as PST/EML/MSG/DBX/MBOX/HTML/TXT/RTF/PDF formats.
    5. You now need to choose the desired format, i.e., PST File (MS Outlook), and tap Next.
    6. You can also filter the data and choose the desired location with saving preferences for your converted file.filter the data
    7. Lastly, tap on Finish, and you are all done now.
  3. Bottomline

    So, these are the possible solutions that you could try if you’re getting the “OST file is in use and cannot be accessed” error. Of course, there may be other potential fixes not mentioned here, but we hope at least one of these suggestions helps to get your Outlook data up and running as smoothly as possible.

    We recommend using our automated solution to fix this Outlook issue, as it quickly converts inaccessible or corrupt OST files into accessible PST files. Try this tool today and see how simple it is to get your data back.

Kernel for OST to PST
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