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Outlook Data File Cannot Be Accessed? Here’s How to Repair it!

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When I was using Microsoft Outlook not too long ago, I saw a message that said there was a problem with the accessibility of its .OST file: error 0x800401F Outlook data file cannot be accessed.” .OST (Offline Storage Table) files are of the utmost significance since they enable us to access Outlook data even when we do not have an active internet connection. However, Outlook may have issues if the .OST file is damaged or unable to be accessed by Outlook.  In this article, I’ll tell you what to do if you can’t access your Outlook data file.


Common Accessibility Errors with Outlook

Before diagnosing this issue, we must look at some of the more typical accessibility problems that typically occur in Outlook.

  • The .OST file cannot be found in any location or on any device.
  • Outlook is unable to show the collection of folders and files.
  • The .OST file is already being used by one of the supported applications.
  • The user cannot view the .OST file because it has been locked.
  • Another user is now accessing the .OST file – for instance, a file is either still running or being accessed.
  • Closing any other applications that are currently utilizing the .OST file.
  • Unable to find either the file path or the storage location for the .OST file.
  • The default .OST file cannot be seen because another program is now using it.
  • Due to an error that occurred with Outlook, it cannot load the requested .OST file.

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Why Outlook Cannot Access an .OST File?

As we discussed earlier, several issues might contribute to the Outlook data file inaccessibility problem. Consequently, if you are unable to access an .OST file in Outlook, you should make an effort to analyze the situation, as it may be caused by one of the following issues:

  • Inaccessibility:The .OST file you want to view may not be present in its original place, rendering it inaccessible (i.e., the file could have been moved or deleted).
  • File Corruption: You can see this error if the .OST file you are attempting to open has been corrupted by another program, a virus, or both.
  • Unauthorized Access: If you are not the Administrator of the .OST file or do not have the appropriate authority to access the .OST file, then this can lead to a problem with the file’s inaccessibility.
  • Synchronization Issues: The issue may have arisen due to syncing errors between Outlook, Exchange, or your email server.
  • Corrupt Add-Ins: This problem might occasionally be caused by unwanted or corrupt plugins (Outlook add-ins).
  • Other Reasons: In addition, the difficulty might be caused by a sluggish network connection, a firewall provided by a third party, issues with the server, incompatible data, etc.

How to Solve the “MS Outlook OST File Cannot Be Accessed” Problem?

Now that we have gone over all the fundamentals, let’s learn how to repair the Outlook data file that cannot be accessed, by adopting various methods shown here.

Method 1: Turn off the Compatibility Mode in Outlook

Outlook, like other pre-installed programs in Windows, can operate in a compatibility mode. Unfortunately, if the mode has been activated, it may create problems with the stored .OST file’s accessibility.  Suppose you cannot view an .OST file in Outlook, you can go to the directory in which the Outlook.exe file is located. You can choose to go to its location directly or search for it using the search tool on the taskbar.

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Once you have located the Outlook.exe file, right-click on it, and select Properties. Once you have the Properties box open, go to the Compatibility tab. From there, ensure that the option to Run this application in Compatibility Mode is disabled.

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After that, you can relaunch the Outlook application, and you should have no problem accessing the .OST file you previously saved.

Method 2: Get Rid of Faulty Outlook Add-ins

If Outlook cannot access .OST files as explained above, the problem might lie with one of the plugins you have installed. Thank goodness you won’t have trouble removing any add-ins installed on your Outlook account. Run Microsoft Outlook, then go to the File > Options > Add-ins menu option.


Go to the Manage area of the Outlook Options box, and select COM Add-in from the list of available options. This will bring up the add-ins installed on your computer, allowing you to remove any plugin from Outlook. To deactivate an add-in, you have to make your selection, then click the Remove button in the toolbar.


Method 3: Turn off the Exchange Cached Mode for your Account

The problem where an Outlook data file cannot be accessed can sometimes be traced back to synchronization issues between Exchange and Outlook. Simply turning off the cached mode in MS Exchange will allow you to overcome this problem.

Go to Control Panel > Mail > Email Accounts, choose the email account you want to change, and then click the Change button. Next, you need to go to the Advanced Settings section of your user profile and deactivate the Exchange Cached Mode function.


Method 4: Use Scanost.exe to Repair the .OST File

If the .OST file you’re attempting to access is corrupt, you’ll have trouble accessing it. The good news is that Windows has a built-in solution called the Outlook Inbox Repair tool that can repair damaged .OST files.

Begin by locating the Scanost.exe program on your computer – you can often find it in the directory – C: > Program Files > Microsoft Office. When you first run the Scanost.exe program, the user interface of the Outlook Inbox Repair utility will appear on the screen. You can now navigate to the .OST file, and load it to restore and correct it without difficulty.


Method 5: Repair the Installed Outlook Application

A defective application is yet another potential cause of the problem with the Outlook data file that prevents access to the file. In this scenario, you can easily repair the Outlook program by running a pre-installed troubleshooter on Windows.

You can pick the MS Office program already installed on your computer by navigating to the Settings > Apps and Features menu option. In addition, you now have the option to Modify the MS Office application that has been installed.


Now, select the Repair option from the drop-down menu when it offers choices to reset or repair Microsoft Office. This will launch a new process for you to complete, to execute a speedy online repair of the Office apps installed on your computer.


Method 6: Convert the Corrupt .OST File to Another Format (like .PST)

Finally, if Outlook cannot open an .OST file, you can export it to another program. Recovery Toolbox .OST to .PST File Converter is a helpful tool you can use if you want to solve this problem.


Convert it online and load the corrupted .OST file. After that, you can begin the conversion process; the data will be exported in a format compatible with .PST without any issues. After the process, you can see your data, export the .PST file, and open it in any other program, such as Thunderbird, Mail Spring, Mail Bird, and so on.


Method 7: Use Recovery Toolbox for Outlook to fix your corrupt. PST file


With Recovery Toolbox for Outlook you can fix any .PST files of different versions: ANSI (Outlook 97-2003), Unicode (2007 and above), and repair password-protected files. The online Outlook recovery tool makes it easy to fix the error online on any device. In addition, you’ll have no difficulty fixing encrypted .PST files and restoring .OST files of any version.

After reading this article, you’ll without a doubt discover a solution to the issue where an Outlook data file cannot be accessed. Whenever Outlook is unable to access an .OST file, the first thing I do is either stop any firewalls or remove any unnecessary plugins. In addition, if you cannot view .OST files in Outlook, you can attempt to fix them or convert them to a .PST format using Recovery Toolbox for Outlook. Both of these options are available to you and easy to use. In addition, this method makes it simple for you to access the data stored on Outlook or any other email service.


Kossi Adzo is the editor and author of He is software engineer. Innovation, Businesses and companies are his passion. He filled several patents in IT & Communication technologies. He manages the technical operations at

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