OST is not an Outlook data file is an error that users complain about using the Outlook app, and it may occur for several reasons. However, this article will discuss the cause of the error and how you can fix it.

Users need the OST file to synchronize offline data

  • Exporting OST files is not possible unless you convert them to PST.

  • Users may encounter issues with the OST file if it is corrupt.

  • Using an OST to PST converter app can fix the issue in no time.

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Microsoft Outlook is one of the best tools for managing personal information such as webmail, contacts, calendar entries, and lots more.

It has many features that make it better than other software in the market. One of the advantages of using Outlook is that users can work on it when offline.

Though you need an internet connection to connect with Outlook servers, users can work offline and sync it later whenever there is an internet connection.

Furthermore, using Outlook without a network connection enables the Offline mode. It works with an OST file (Offline Storage Table), an Offline Outlook data file used to store your activities while disconnected from the servers.

Hence, the copy saved on the OST file is synchronized with Outlook when there is an internet connection.

Is Outlook OST a data file?

Outlook OST is an Offline Outlook Data File that allows you to store all the work you have done while offline. It contains a synchronized copy of mailbox information on a local computer.

So, without the Outlook OST data file, users won’t be able to synchronize the offline Outlook data.

Can we convert OST to PST?

Users can convert OST files to PST files. However, it may be for reasons such as exporting or accessing the OST file on another computer or exporting it for someone else to use.

Hence, we recommend you read our article about saving your Outlook emails using OST to PST Converter for more information.

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How do I fix OST is not an Outlook data file?

1. Recreate the OST file manually

  • Open the Control Panel and click on Mail.
  • Click on Show Profiles in the Mail Setup.
  • Select the default profile and click on Properties.
  • Click on Exchange Account and tap on Change.
  • Then, enable the Use Cached Exchange Mode option.
  • Navigate to More settings, select Offline folder file settings and disable the offline use option.
  • Then, click Yes.
  • Go to Cached Exchange Mode settings, enable Use Cached Exchange Mode and click OK.
  • Click Next and the Finish option.

It will help fix the Outlook data file.ost cannot be opened error.

2. Delete the OST file

  • Open the Control Panel and click on Mail.
  • Click on Show Profiles in the Mail Setup.
  • Select the default profile and click on properties.
  • Select Email Accounts, go to the Data Files tab, and click on Open File Location.
  • Right-click on the OST file in the source directory and select Delete.

After the process is complete, launch Outlook. It’ll automatically recreate the OST. It is the best fix for fixing the error message: The set of folders cannot be opened – the file is not an Outlook data file.

3. Use an OST Converter Application

  • Download the OST Converter, then launch the software on your PC.
  • Navigate to the OST file from the PC.
  • Click on Mail to preview the Data on the OST file.
  • At the top of the screen, click on Export to convert the OST file data.
  • Select PST and click on Export.

Exporting the OST file to PST allows the user to import the PST file into the Outlook application.

4. Restart your PC

  • Click on Start.
  • Select Power.
  • Click on Restart and OK.

Restarting the PC will fix startup issues affecting the file.

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5. Update Outlook on your PC

  • Launch Outlook on your computer and navigate to the file.
  • Click on the Office Account.
  • Select the Update Options and click on the Enable Updates option or Update Now.
  • Restart your PC.

What is the difference between .PST and .OST in Outlook?

Outlook PST Files can store local copies of your email data. Also, users can export and import tasks, messages, contact, etc., to any PC.

However, Outlook OST files allow you to store work done in offline mode and can only be synchronized individually using Outlook servers. Likewise, exporting is not possible unless converted to PST.

In conclusion, we recommend you read our article about saving your Outlook emails using OST to PST Converter in a few minutes.

Also, you can go through our guide on recovering deleted/archived Outlook messages to retrieve your data.

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