Fix the Outlook error “Ost is not an Outlook Data File”

OST to PST Converter /February 05, 2025

Summary

Microsoft Outlook OST files store your crucial business data but are prone to getting damaged or throwing errors. One such error is “OST is not an Outlook data file”, which leads to data inaccessibility. In this blog, we will learn about the root cause of this error, along with reliable methods to fix the OST file. However, you can fix the inaccessibility of your OST file by converting it into PST using the advanced Goldytools OST to PST Converter

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Introduction

Microsoft Outlook is a reliable email that allows users to work in offline mode by creating a synchronized copy of their entire Exchange Server data. It lets you work freely on the offline OST file when disconnected from the server and automatically updates the data after the connection is restored. The issue arises when Outlook is not able to read or access the OST file & its data due to “OST is not an Outlook data file” error. These issues can occur after procuring corruption & bringing downtime, and also risk on your sensitive data, so you need to repair the OST file to proceed required operations.

There can be some common reasons behind the occurrence of errors where you will see a popup message on the screen showing:

““Cannot start Microsoft Outlook. Cannot open the Outlook Window. The set of folders cannot be opened. The file c:\Users\USERNAME\Local\Microsoft\Outlook\abc@xyz.com.ost is not an Outlook data file (.ost).””

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What results in “OST is not an Outlook data file”

Microsoft Outlook is indeed a reliable collaborative platform for organizations that are managing their business. But, the occurrence of errors is very common while using an OST file, which can be derived from different reasons. By undertaking the respective measures you can avoid experiencing such errors. Let’s discuss some of the most common reasons behind such errors:

  • Corruption: OST files often get corrupted which is a very common phenomena, and it can happen at any time due to many issues.
  • Sudden shutdown: Instances where the software and system gets abruptly shutdown, so it can severely damage your OST file.
  • Outlook version: The compatibility issue in Outlook version can slowly damage your OST file, so you should update your Outlook to the latest version.
  • Virus or malware: One of the most common yet dangerous causes of OST file related issues are virus attacks that highly affect the valuable data.
  • Synchronization failure: The connection failure between the OST file and Exchange Server can also throw OST is not an Outlook data file error.
  • Oversized OST file: Heavy flow of mails are received on the Exchange Server on a daily basis as it is synced with the OST file, that makes the OST file very large.

How to fix the “OST is not an Outlook data file” error?

Experiencing an OST file issue that prohibits your access to its data or not being able to open it and leaves the data at risk. This instigates the need to find prominent ways to repair OST file errors and secure business’s useful data. Find the effective manual methods to fix OST file errors:

Method -1 Create a new OST file

To fix the corruption in the OST file which stops you to open or makes it inaccessible.So, in such cases you must delete the old OST file and then create a new file. Below the

  • Locate the OST file from the system, and you can use the default location – C:\Users\AppData\Local\Microsoft\Outlook\.
  • Browse the corrupt OST file from the system and delete it.
  • After this, launch the Outlook application as it will automatically create a new OST file.

Method -2 Disable add-ins in Outlook

In Microsoft Outlook, users often include several add-ins to enhance the functionality but it sometimes invites errors due to bad configuration. So, we suggest you to remove add-ins by following the methods mentioned below:

  • Launch Outlook application.
  • Go to Files and click on Options.
  • Now, from the Add-ins de-select the add-ins you want to remove.

Method -3 Check for updates

It is very necessary to manage proper technical requirements to run both applications and files safe from unpredictable errors “OST is not an Outlook Data File”. So, you must check if your Outlook application & Windows is up-to-date or not. To update both Windows and Microsoft Outlook follow the steps below:

  • Launch Outlook application and go to Files.
  • Click on Office Account>Update Options where you can see if there is any update or not.
  • If there is an update available then click on theUpdate Now option.
  • After the update, then restart the applications.

Updating Window

  • In the Search bar type Settings and open it.
  • Now, go to Windows Update.
  • If it’s showing any new updates, then click on it and update the Windows to the latest version.

Conclusion

Microsoft Office 365 users often keep their data within the Offline OST file and forget to back it up to different locations. The possibility of experiencing errors like “OST is not an Outlook data file” is always high and, if the data is not backed up then you might lose it forever. In the above article, we have mentioned some useful methods that can help you to fix this error. But, there are some instances where your Outlook account gets damaged, and you can’t even configure the OST file to Outlook. So, we recommend you integrate a reliable Goldytools OST to PST Converter tool that easily exports and saves your corrupt or damaged OST file in PST file format.

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