Fix OST is Not an Outlook Data File Issue: 6 Easy Methods!

Updated On - May 30, 2024 by Nasir Khan | Reading Time: 6 minutes

Summary: This comprehensive guide provides 6 easy-to-follow methods to resolve the common problem of ‘OST is Not an Outlook Data File’. The aim is to help users overcome this problem in their Outlook application to ensure a smooth email experience. Corruption or malicious data available in your OST file is one of its prime causes. Therefore, it also introduces an OST Recovery Tool to repair corrupt or damaged OST files.

As an Outlook user, you are familiar with the OST file that gives access to work offline. This OST file plays a crucial role in providing flexible and offline access to improve the performance of Outlook. However, various instances occur where users have encountered different issues in Outlook. One such error is that OST is not an Outlook Data File. It means that Outlook does not recognize the OST file and causes trouble to have a smooth mailing experience.

Fix OST is Not an Outlook Data File Issue

Now, the question is how to solve OST is not an Outlook Data File. To answer this, first, you should analyze its possible cause. It helps to understand why this error occurs in your Outlook.

Why OST File is Not Recognized by Outlook?

Unfortunately, the specific cause of this error is not recognized yet. However, this section helps you understand the various factors that can cause the OST is not an Outlook data file issue.

  • Corrupt or damaged OST file.
  • Corruption or misconfiguration of the existing user profile.
  • Synchronization error between the OST file and the Exchange server.
  • Interference due to overly aggressive antivirus or security software.
  • OST file is moved or stored in an inaccessible location.
  • Large OST file especially in older versions of Outlook.

These are some of the reasons that cause the OST file cannot be opened in Outlook error. Now, let’s proceed with 6 effective methods to resolve this issue.

06 Manual Methods to Fix OST Not an Outlook Data File Error

Unlike PST, you can’t access OST file data from other Outlook accounts. Further, it is recommended to have a backup of your OST file data before moving ahead with the methods to fix it. For this, you can utilize a reliable OST to PST Converter that facilitates you to access the OST file from another Outlook account.

Method 1: Update Windows and Restart Your Device

To improve the performance of your Windows device, Microsoft regularly releases updates. Therefore, ensure that your device is up-to-date. To verify this, go to Settings and click on the Windows Update option to check for any updates. After updating Windows, restart your device and open Outlook to check if the error is resolved.

Method 2: Repair Your Existing Outlook Profile

This method is helpful to reconfigure your account’s settings, including the OST file location. You can perform the following steps if the error persists due to the storage of the OST file in an inaccessible location.

  1. Open the Control Panel from the Start Menu.
  2. Search for the Mail option and click on Mail (Microsoft Outlook) (32-bit).
  3. From the Mail wizard, click Show Profiles and select your Outlook profile.
  4. After that, click Properties to choose the Email Account that you have configured in Outlook.
  5. In the end, click the Repair option and follow the on-screen instructions to repair your Outlook profile.

Method 3: Creating a New Outlook Profile

This method often helps to resolve and repair the ‘OST is Not an Outlook Data File’ error. You can follow the given steps to create the new Outlook profile.

  1. Open the Control Panel on your system.
  2. Find and click on the Mail (Microsoft Outlook) (32-bit) option.
  3. Now, click on the Show profile >> Add and enter a new profile name. Click on the OK button. OST is Not an Outlook Data File
  4. In the Add Account window, provide your name, email address, and password.
  5. Click Next and select the new profile to enable Always use this profile as the default.Why OST File is Not Recognized by Outlook
  6. In the end, click OK and open the Outlook application again.

This method helps to fix OST file synchronization error, which results in Outlook not recognizing the OST file issue.

Method 4: Disable or Turned Off Cached Exchange Mode

You can also turn off the Cached Exchange Mode to fix this error. However, it won’t allow you to use Outlook in offline mode. The following steps helps you to disable it effectively without affecting the other settings.

  1. Open the Outlook application and navigate to File > Account Settings > Account Settings.
  2. Now, choose your email account and click on the Change option.
  3. Here, uncheck the Use Cached Exchange Mode and click Next.Disable Cached Exchange Mode to resolve OST is Not an Outlook Data File Issue
  4. A pop-up appears, click OK and then Finish to apply changes.

After that, launch Microsoft Outlook and verify if the error has been resolved. If the error persists, you can recreate the Outlook OST file by following the next step.

Method 5: Recreate a New Outlook OST File

This method helps you to move the inaccessible OST file to a different location. So that you can recreate the Outlook OST file to fix Outlook cannot open OST file error.

  • Go to the OST file location on your system. Recreate a New Outlook OST File to fix the issue
  • Change its name to something like old.ost for backup. You can also delete this file if you have stored its backup.
    Then, open Outlook. It will automatically recreate a new OST file in the default location.
  • If the above methods won’t fix the “OST is Not an Outlook Data File” error, it is recommended to use the Microsoft Recovery Assistant.

Method 6: Microsoft Support & Recovery Assistant

It is a free utility to diagnose and fix errors with the Outlook application or the system. It runs a few tests on your system and provides the best solutions to resolve the identified issues.

  • Download and Install the Microsoft Support and Recovery Assistant. Microsoft Support & Recovery Assistant to resolve Outlook error
  • After installation, click on the I agree button.
  • Select Outlook from the options available in its wizard.
  • Choose Outlook Won’t Start or Other Problems and click on Next.
  • Follow the on-screen instructions to diagnose and fix the Outlook profile issues.

Use Professional tool to Fix OST is Not an Outlook Data File Issue

If none of the above solutions help, you can opt for an advanced solution to recover your data from the corrupt OST file. In this regard, the Regain OST File Recovery Tool is the most prominent utility to retrieve your data. The best thing about this utility is that it offers several advanced features to ensure the recovery of all the data from your corrupt OST files. Using this utility, you can also extract deleted emails successfully. Furthermore, it facilitates you to restore data in multiple file formats, including EML, PST, MSG, MBOX, ICS, VCARD, and HTML.

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It is crucial to fix the “OST is Not an Outlook Data File” error for a seamless email experience in Microsoft Outlook. The above-explained six methods help you to resolve this issue. Moreover, using advanced utilities such as Regain OST File Recovery Tool provides an advanced solution to recover and restore the data from corrupt OST files. By following these methods and utilizing this advanced utility, you can overcome this issue and ensure optimized Outlook usage.

Frequently Asked Questions

Ques1. How do I convert an OST file to Outlook data?
Ans. The simple solution is to export OST to a PST file that can be imported into any Outlook profile. Further, you can share this PST file with other Outlook users to transfer the data. A reliable OST File Converter tool is one of the best ways to perform this task.

Ques2. Can I open OST file in Outlook?
Ans. OST file is an offline data file automatically created in a default location on your system. Unfortunately, you can’t open the OST file in Outlook. However, you can convert it into PST format, which you can import into your Outlook profile.

Ques3. Where is my Outlook OST file?
Ans. In Outlook 2019, Outlook 2016, Outlook 2013, and Outlook 2010:

The default location for the OST file is typically under the following path:

In Outlook 2007:
The default location for the OST file is under
C:\Users\YourUsername\Local Settings\Application Data\Microsoft\Outlook

Note: “YourUsername” is the actual username of the user account.

Author: Nasir Khan

I am Nasir Khan from India, working as a Content Developer in Regain Software. Here I am writing about our products and their updates. And writing some free solutions from converting emails or Cloud Migration process. We have tools like Email Converter, Emails backup and Cloud migration.

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