OST File Corruption Issue: A Comprehensive Guide

Updated On - June 7, 2023 by Henry Bray |

Reading Time: 8 minutes

Emailing is one of the significant aspects of professional and personal life; hence email data is crucial. Outlook is a prominent email client, and all users are exceptionally versed in the data storage file formats. Outlook users are familiar with the term “OST corruption” While dealing with Outlook for Windows or Mac applications. Though users take many precautions to prevent accidental data loss and corruption, but, mishappening can happen to anyone. But what should you do if your offline OST files somehow get corrupted? Today, we’ll talk about how to delete corrupt OST files in Outlook and your other choices to access corrupt OST files. Also, we will cover all the dimensions of OST file corruption.

What is a corrupted OST file?

An OST or Offline Storage Table file is a local copy of your mailbox stored on your computer. It is used in Microsoft Outlook to allow users to access their email, calendar, and contacts even when not connected to the internet.


corrupted OST file can occur if the file becomes damaged or is otherwise unable to be read by Outlook. This can happen for various reasons, including hardware or software issues, power outages, or problems with the Exchange server. If an OST file becomes corrupted, it can cause Outlook to malfunction or display errors when trying to access the file.

Location of OST file

Before we discuss how to delete corrupt OST files, let us first determine the location of the OST file. The location of the OST file depends on the version of Outlook and the operating system you are using. Here are some of the typical locations of OST files:

  • Outlook 2019 and Outlook 2016: C:\Users%username%\AppData\Local\Microsoft\Outlook
  • Outlook 2013: C:\Users%username%\Documents\Outlook Files
  • Outlook 2010: C:\Users%username%\AppData\Local\Microsoft\Outlook

Note: %username% refers to the username of the currently logged-in user.

How do OST files get corrupted?

OST files can corrupt for various reasons, such as power outages, system crashes, and malware infections. Let’s learn them one by one!

  • Sudden power failure or shutdown can be a reason behind OST corruption.
  • System Hardware issues (like; hard drive failure) can also cause OST file corruption.
  • Network issues that disrupt communication between the Exchange server and the local computer
  • Virus or malware infection is also one of the common reasons responsible for OST file corruption.
  • Improper closing of Microsoft Outlook while the OST file is in use is also not good for the file’s health.
  • Incorrect systems or wrong Outlook configurations can also corrupt the file.

If an OST file becomes corrupted, it may be difficult or impossible to access the data it contains. Sometimes, you can repair the OST file using Microsoft Outlook’s built-in repair tool. However, if the damage is severe, you may need to recreate the OST file by synchronizing with the Exchange server again or have to use third-party OST recovery tool.

What errors occur in Outlook as a result of OST corruption?

A corrupt OST file can cause Outlook to crash or freeze, preventing you from accessing your important email and other data. Besides, it causes a lot of unwanted errors that have listed as follows:

  • Due to corrupt OST files, Outlook may crash randomly.
  • You will not be able to pen the Outlook data file.
  • Users may face data sync issues between Outlook and the Exchange Server.
  • One of the ordinary and main errors that users face is the inability to send or receive emails. For an email client, not receiving/sending is the worst thing that could happen to any email user.
  • Corrupted contacts and calendar entries also signify corruption.
  • Lost IMAP and POP3 settings and configurations also indicate corruption.
  • Outlook fails to start and displays an error message.
  • Outlook takes a long time to start, and processing gets very slow; hence process gets tedious and time-consuming.
  • Error alerts suddenly pop up that show the OST file is inaccessible.
  • Blank folders with no content appear in Outlook.

So, it is important to delete corrupt OST file in Outlook or repair it to prevent these issues and keep your email program running smoothly.

How to Delete Corrupt OST Files in Outlook?

  • Close Outlook and any other programs using the OST file.
  • Locate the OST file on your computer. OST files are commonly saved in the C:\Users[Your_Username]\AppData\Local\Microsoft\OutlookHow to Delete Corrupt OST Files
  • Rename the OST file by adding the word “old” to the end of the file name (e.g., “Outlook.ost” becomes “Outlook.ost.old”). This will allow you to keep a copy of the OST file in case you need to refer to it later.
  • Open Outlook and allow it to create a new OST file. This will delete and replace the corrupt OST file with a new, un-corrupted one.
  • Deleting a corrupt OST file in Outlook is an important task. Following the steps outlined above, you can easily delete corrupt OST files and get your Outlook program back up and running. That can help keep your email program running smoothly and prevent data loss.
  1. Recreate OST files in Outlook

Recreating an OST (Offline Storage Table) file can help you fix issues related to synchronization, data corruption, and other errors. When you recreate an OST file, it creates a new one that is synced with the Exchange server.

Before proceeding with the steps to recreate OST files, it is important to understand that recreating an OST file will delete all the data in the file, including any changes you made to your mailbox data while working offline. If important data is not synchronized with the Exchange server, back it up before proceeding.

Here are the steps to recreate OST files in Outlook:

Step 1: Close Outlook

Make sure to close Outlook completely. You can do this by right-clicking the Outlook icon in the system tray and selecting “Close Outlook.”

Step 2: Locate the current OST file

The location of the OST file depends on the version of Outlook and the operating system you are using. You can use the steps outlined in the previous blog post to locate the OST file.

Step 3: Rename the current OST file

To recreate the OST file, you must first rename the current OST file. You can do this by right-clicking the OST file and selecting “Rename.” Change the file extension from .ost to .old.

Step 4: Open Outlook

Open Outlook, and it will automatically create a new OST file synchronized with the Exchange server. The synchronization process may take some time, depending on the size of your mailbox and the speed of your internet connection.

Step 5: Verify synchronization

Once the synchronization process is complete, verify that your mailbox data is up to date by checking your emails, calendar, contacts, and other mailbox items. If you notice any missing data, you can import the data from the backup file you created earlier.

Is it safe to delete corrupt OST files?

Now that we know the location of the OST files, let us answer the question, is it safe to delete corrupt OST files?

The short answer is yes. You can delete the corrupt OST file without affecting your mailbox data, as it is just a local copy of your Exchange server data. However, deleting the OST file will result in losing all the changes you made to your mailbox data while working offline. When you reconnect to the Exchange server, a new OST file will be created and synchronized with the server.

Why should you repair corrupt OST files instead of deleting them

Although it is safe to delete corrupt OST files, it is not the best solution to the problem. Instead of deleting the OST file, consider repairing it. Here are some reasons why:

  • Data recovery: When you delete the OST file, all the changes you made to your mailbox data while working offline will be lost. However, if you repair the corrupt OST file, you can recover all the data before it becomes corrupt.
  • Time-saving: If you delete the OST file, Outlook will have to re-synchronize all the data with the Exchange server, which can take a lot of time, especially if you have a large mailbox. Repairing the corrupt OST file will save you time as you will not have to re-synchronize all the data.
  • Cost-effective: If you use paid data recovery software, deleting the OST file and re-synchronizing the data with the Exchange server may not be cost-effective. Repairing the corrupt OST file with a reliable OST to PST converter software is a more cost-effective solution.

How do I recover corrupt OST files without deleting them?

According to experts, deleting or recreating the corrupt OST file is the easiest option to eliminate the OST corruption issue. But in all cases, it’s not right. Sometimes, you may have vital data saved on your OST file. At that time, you have no other option but to recover the data.

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You don’t need to worry about it, as many third-party tools are available online to perform the recovery. The Regain OST recovery tool is the best; it has all the advanced facilities and a straightforward user interface. Let’s know about this professional utility and know what features it offers to users.

Features and Facilities Offered by Regain OST Recovery Tool:

  • Users can add multiple OST files to recover OST files without any limitations.
  • The size of the OST files also doesn’t matter; the software can recover OST files of any size.
  • After recovering the OST file, it offers multiple file formats to save the data. E.g., PST, EML, MSG, MBOX, vCard, et cetera.
  • Regain OST Recovery Tool also previews the data after recovery and before saving. 
  • The GUI of the tool is very user-friendly. Any user without any prior technical knowledge can quickly and easily recover OST files.
  • The tool properly maintains the metadata integrity and hierarchy of the folders.
  • It recovers all the items of OST files like contacts, emails, calendars, and all. The tool properly works on the hard deleted and severely corrupted OST files.
  • At the end of the process, the tool provides users with a proper report, including all aspects, to save for future reference.
  • Regain OST Recovery Tool is compatible with all versions of Windows O. S. and Microsoft Outlook’s versions.
  • A free demo version of this software is also available to download, which allows processing the 30 items per folder. Users can easily download and recover the OST files and ensure the tool’s working.


Don’t delete corrupt OST files; recover them using professional software:

Below are the simple steps to recover the corrupt OST file and deal with the OST file corruption.

  • Step 1: Install and Open your system’s Regain OST Recovery Software.
  • Step 2: Click on the Add file option and add OST files.
  • Step 3: Now preview the OST file and click the Export option.
  • Step 4: Choose the Outlook PST option in the dropdown menu. Here, you can also choose any other file form as needed.
  • Step 5: At last, choose a required option and click Export.

 So, these were the straight and simple steps to deal with the OST file corruption. You can also save the report or the future references.


Final Words:

File corruption is a common issue in this technical world, and Outlook users are no exception. OST file corruption can be a crucial issue for Outlook users. If your OST file becomes corrupted, it can cause Outlook to malfunction or display errors, which makes it difficult or impossible to access your essential data. To prevent this from happening, you can delete corrupted OST files in Outlook. However, if your OST file keeps the data you need, then deleting is not an option. Using a professional OST recovery tool is the best option in this scenario. You can use the Regain OST file recovery tool to recover lost and inaccessible data from corrupt OST files. Simple steps to run the tool are explained above. Download and install the tool and successfully tackle OST file corruption.


Frequently Asked Questions:


Q. How can I check if my OST files are corrupted or not?

A. A few common symptoms indicate corruption in the OST file. Signs like slow processing, error in sending/receiving emails, error pop-ups, and unable to open OST files indicate OST corruption. If you face this kind of issue, there is a high chance that your OST files are corrupted.


Q. What precautions should I take to prevent corruption in file format in the future?

A. To prevent file corruption, use Antivirus programs, synchronize compatible hardware, and adequately handle Outlook. The improper outage and power cuts should be in check and controlled.


Q.Is there any other option to deal with OST file corruption other than deleting OST files?

A. Recovery of corrupted OST files is the best option. If you delete corrupted OST files, then you will also lose the data within the OST files. To recover OST files, you can use a professional third-party recovery tool.


Q. Can I recover multiple OST files of large sizes in a single go using Regain OST Recovery Tool?

A. Yes, with the Regain OST Recovery Tool, you can recover multiple OST files of any size. The tool keeps the originality and folder hierarchy of folders intact.


Q. I am not a technical guy. Can I recover the OST file on my own using Regain Software?

A. Regain OST Recovery Tool has a straightforward and easy-to-understand GUI—any technical or non-technical user can efficiently process the tool. You can contact Regain’s team for help if you still need any assistance. Regain’s technical support team will help you out with the OST recovery.

Author: Henry Bray

Henry Bray is a young technologist and content a Content Writer at Regain Software, loves to write about MS Outlook, MS Exchange Server, Office 365, Mozilla Thunderbird and many more email applications.

3 thoughts on “OST File Corruption Issue: A Comprehensive Guide”

  1. Avatar Sonia says:

    I have noticed that Outlook’s offline OST files often get corrupted. I agree with your thoughts that deleting the corrupted OST file is the best way. Thanks for this tedious article! I have found many useful pieces of information (like the OST file’s location, screenshots of the steps, and others) here. Again, thanks a lot.

  2. Avatar Marina Barros says:

    I was having a lot of trouble with this problem, but I’m now able to repair it. Thank you for the informative information!

  3. Avatar Scott Newman says:

    It is never a good idea to delete OST files; instead of deleting them use any automated tool and recover them. Business data is the backbone and losing them cause trouble or you might need the deleted OST files data later.

    I truly agree with not deleting corrupted OST files data, and after reading the complete blog using your free OST recovery tool, there is no reason to delete OST files. You make the OST recovery process easy as it never was. Appreciate your effort and effortless tool.

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