Reasons behind OST file corruption and solutions

Reasons for Corrupt OST file and Methods to Fix OST File Corruption

One of the most frequent queries that Outlook users have is OST file corruption. So, in this article, all about the OST files, common reasons behind its corruption in Outlook 2016, 2013, 2010 and 2007 have been explained along with the possible manual solution to fix these corruptions.

OST files- An overview

OST files in Outlook are nothing but a replica of the mailbox contents of users which is stored on an Exchange Server. Due to this, Outlook remains in function continuously even when there is Exchange cached mode. Sometimes, when the user uses to work offline because of certain reasons, OST files allow working in offline mode too. It is so because the mailbox copy which is available locally makes the data accessible.

Once the connection rebuilds, there is automatic syncing of the OST file with the Exchange Server mailbox. This seems so smooth, but in reality, it is not like that. As in other apps and files, corruption occurs. The same is the case with OST files. In most cases, there is OST file corruption due to an internet connection problem.

What causes OST file Corruption?

During the synchronization process of OST, if there is an interruption due to poor internet connectivity, there are chances that OST files may get corrupted. Once there is an interruption in OST files, the functionality of Outlook also gets affected. Apart from these reasons, there are also several other reasons behind OST file corruption. These reasons are categorized into Hardware related issues and Software related issues.

Hardware related reasons

As the name suggests, these issues are due to any problem like improper configuration, failure, or malfunctioning in the external components of the computer system. These are some of the reasons which come under Hardware related issues.

• Affected Storage Device:

If your storage device seems slower than usual, there might be many reasons behind the problem like bugs or faulty hardware. The slow performance of your storage device is a result of malfunctioning of hardware components or any viral infection to the system.

• Bad Sectors on the Hard Drive

It is one of the major reasons behind OST file corruption. It severely affects the working parameters of the hard disk drive due to which there is an impact on its performance. Also, it causes corruption in the data files stored on it. Thus, OST file corruption is also the result of such bad sectors on the device.

• Interruption due to Network Connectors

Certain issues which arise due to inappropriate functioning of routers, cables, network cards and other similar devices make an impact on the accessibility and functionality of OST files as a result of which it fails to sync in a proper manner. So, better check the network connections to be ensured about their working.

• Sudden Power Loss/Surges

Sometimes, sudden power failure is also the reason behind OST file corruption if the user is currently accessing the file and working on it. There are also instances when corruption is due to excess power supply and sudden loss of electricity.

Software related reasons

If there are issues due to logical incompatibilities and inconsistencies, all these come under software related problems. Also, these errors are caused due to bug transmission, virus infection, application failure and downloading the applications from some untrusted or unreliable sources. Some of these errors have been explained below.

• Abnormal Termination of Outlook

Always exit all the dialog boxes, opened windows, emailing function or any application once you are done with that in MS Outlook. Also, remember that you shouldn’t close the application in process. This may turn your OST files corrupted and your Outlook data will be inaccessible. In some cases, the application shutdown itself.

• Stipulated Storage Limit

It is a known fact to all that each and every file being individually used for the storage of data is liable to specific capacities of storage. When the data stored in OST files reaches to the specified limit, there is corruption. You’ll have to repair these corrupted files in order to regain the incorporated data and to fix the OST file corruption. Thus, it is wise to compact the OST file and split it on a regular basis.

• Deficiency in Outlook Program

In some cases, the problem arises with application itself because of certain issues in OST or PST files. In such a scenario, it is difficult to detect the actual reason. But, using several techniques, you can detect the cause and fix it.

• Incompatible Outlook Add-in

Sometimes, there is a problem with the add-ins, which are installed on your system with Outlook. To get rid of this, you need to disable COM add-ins from the Outlook. You can do so by going on Add Ins option and after that clicking on Manage. You should disable these add-ins on “one-on-one” basis so that you get to know which add-in was creating the problem.

Effective Solutions to Fix Corrupt OST File Problems

Solution 1: Update the Folder

This method allows to change the properties of the folder to repair the inaccessible OST File issues. Use these steps for Outlook 2010:

  1. Right-click on the folder and click on Properties.
  2. A new dialog box will be appeared. Click on the option ‘Clear Offline Items’ and hit a click on OK button.
  3. On the Outlook 2010 ribbon, select the option of Send/Receive.
  4. Click on the Update Folder to save the changes.

Solution 2: Recreate OST file

As the Microsoft Exchange Server uses OST files for all its functioning. So, If you encounter any issues with the OST file, you can delete that and re-create it by downloading from the server. However, use this method only when you are not able to use your OST files anymore and follow the procedure with utmost care.

Solution 3: Use scanost.exe Tool

Microsoft facilitates the users with two inbuilt tools i.e. ScanPST.exe or Inbox Repair tool and scanOST.exe or OST Integrity Checker to fix some minor glitches in Exchange OST files. The Scanost.exe tool scans all the mailbox items contained in OST files and are present on the Exchange server. This tool assists the users to fix the reasons of the minor issue OST file corruption issues.

But, the OST Integrity Checker is present only in the earlier versions of Outlook i.e. Outlook 2007 and previous versions and has been discontinued from Outlook 2010 and later versions. However, you can take the help of  Inbox Repair tool to resolve the errors of both PST and OST files in that versions of Outlook.

Limitations of Scanost.exe tool

There are some sorts of limitations associated with scanOST.exe or OST integrity checker such as:

  • Not able to recover missing emails or other items from OST file.
  • Can fix only minor corruptions in OST file.
  • No safety assurance while recovering the data.
  • Not present in Outlook 2010 and higher versions.

Solution 4: Start MS Outlook in Safe Mode

The primary reason to start Outlook in safe mode is to disable the add-ins that might arise the errors during the boot process. It enables to work safely without any corrupted add-ins or files. You can simply use the “outlook.exe /safe” command to open Outlook in safe mode.

Solution 5: Compressing the OST file

A large-sized OST file might cause various hassles and glitches such as sluggishness in Outlook performance, OST file corruption, etc. Deleting these files is not the exact solution as even after the deletion of file or an item in the file, it still exists in the deleted folder. For deleting the items which exist in your “deleted items folder”, you need to individually delete all the items which will take a lot of time. So, an alternative is to compact the OST file. By compacting the OST files, extra space occupied by these files gets reduced.

Solution 6: Disable Anti-virus & Firewall settings

You can turn off the antivirus program and other firewall settings. These programs scan and detect every outgoing and incoming email. Due to this,  sometimes, these programs block the normal functioning of Outlook. So, it is recommended to disable the settings of antivirus programs and restart MS Outlook.

Solution 7: Using Professional Tools to Fix Corrupt OST File

If none of the above manual methods work, you can opt for a professional OST to PST Converter to fix the OST file corruption. This tool is very effective as it repairs and fixes all the types of corruption and restore back the data files.


At the times, when OST file corruption is unpredictable in the Outlook data files, users can adopt the above explained manual and automated methods to fix the OST file corruption. Hope this blog is helpful to the users.

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