Solved Error – Outlook OST File Cannot be Opened Windows 10

Summary: In this blog post, you will learn about “Outlook OST file cannot be opened” error and the reasons behind this error. We have shared various solutions to fix this error. We have also mentioned about an advanced OST to PST converter tool that you can use to recover your mailbox data from an inaccessible OST.

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Outlook is an advanced email client that offers a wide range of collaboration, messaging, and security features. Still, it can occasionally run into problems and throw errors, such as “Outlook OST file cannot be opened”. This error usually occurs after a specific event, such as Outlook upgradation and reinstallation. In Outlook the set of folders cannot be opened OST error may also occur when the Outlook data file becomes corrupt or damaged. In this post, we’ll be sharing some effective solutions to resolve this error.

How to Fix “Outlook OST File Cannot be Opened” Issue?

You can first try some simple fixes to resolve the OST data file cannot be found or opened problem. If you’ve installed an Office update or reinstalled Outlook recently, simply reboot the system. This may help you fix the error. If this is not the case, check for new Office updates and install the available updates. Now, see if that fixes the problem.

Outlook data file OST cannot be opened error window
Image 1: Outlook data file OST cannot be opened error window

In some cases, the Outlook data file cannot be opened error is caused by customizations made in the navigation pane. To remove these customizations, go to the Windows Run utility and execute Outlook.exe /resetnavpane.  

If none of these fixes work, follow the given solutions:

 1. Repair OST File

The error OST file cannot be opened is often occurred when the OST file is corrupt. You can repair OST with Outlook’s in-built utility called ScanPST.exe, which is located in Outlook’s installation directory.

However, ScanPST.exe may fail to repair large-sized and severely corrupt Outlook data file. In such a case, you can delete and recreate the OST file. To do so, follow these steps:

  • Close Outlook and delete the OST from your system. If you don’t know its location, enter %LOCALAPPDATA%\Microsoft\Outlook\ in Windows Search and press Enter. You will be taken to the folder where the OST is located.
  • After deleting the OST file, start Outlook. Outlook will automatically recreate OST on your system.

However, for some users, recreating OST is not possible even if they want to fix the problem of OST cannot be opened. This is because of several reasons:

  • Recreating OST is not possible, if the live mailbox is inaccessible due to decommissioned server or lost credentials.
  • If the OST file size is too large, downloading the entire file from server is problematic or almost impossible.
  • If there are some local-only items in OST, the recreated OST won’t have these items.

In such cases, the only option is to recover data from the OST by using an advanced OST converter tool, such as Stellar Converter for OST. The software easily converts an inaccessible OST file to PST, which you can import into Outlook and access your mailbox. This is the ultimate solution when you can’t fix the Outlook OST file cannot be opened issue.

How to use Stellar Converter for OST?

To extract and convert data from OST by using Stellar Converter for OST, follow these steps:

  • Download and install the software.
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  • Launch the software and under the Home tab, click the Select Outlook OST button.
Stellar converter for OST file selection window
Image 2: Stellar converter for OST file selection window
  • Click the Browse button and locate the OST file on your system. If you don’t know the location, click the Find button. Then click Convert to begin the file conversion process.
  • Once the file is converted, preview contents of the file in the preview pane.
Stellar converter for OST file preview window
Image 3: Stellar converter for OST file preview window
  • Select the items you want to save to PST file and click Save Converted File button under the Home tab. This will open the Save As window.
Stellar converter for OST file file format selection window
Image 3: Stellar converter for OST file file format selection window
  • Select PST from the list of options and click Browse to provide the location where you want to save the file.
  • Click OK to save the file at the desired location.

2. Repair Outlook and Install Updates

If there is a problem with your Outlook software, you may encounter the OST cannot be opened error. In such a case, you can repair Outlook with Office Repair. You also need to install new Outlook updates after repairing the application.

3. Disable Conflicting Add-Ins

If an Outlook add-in is conflicting with the application, it may prevent Outlook from opening OST. To disable the faulty add-in and fix Outlook OST file cannot be opened issue, follow these steps:

  • Go to Windows Start menu and search “Run”.
  • Launch Run utility and enter outlook.exe/safe in the input field. Then click OK. This will open Outlook in safe mode.
  • In Outlook, open the File tab and then go to Options > Add-ins
  • In the Outlook Options window, find the Manage section at the bottom. Make sure COM Add-ins option is selected in the drop-down menu, and then click Go.
Outlook add-ins list
Image 4: Outlook add-ins list
  • Unselect all add-ins and click OK.
  • Close Outlook and reopen it in normal mode. If it doesn’t throw the OST cannot be opened error, it means the problem was caused by a conflicting add-in. To identify this add-in, enable one add-in at a time. Once you find the add-in that’s causing the problem, you can remove it from the application.

4. Create a New Outlook Profile

The Outlook OST file cannot be opened issue may also occur due to a corrupt Outlook profile. You can delete your existing profile and create a new profile to resolve the error.


In Outlook the set of folders cannot be opened OST error may occur due to missing Outlook update, a faulty add-in, damaged/corrupt OST file, etc. However, you can easily resolve the error by following the solutions mentioned in this post. In case your OST file becomes inaccessible, you can use an advanced OST to PST converter software such as Stellar Converter for OST to extract data from OST. The software converts OST file into Outlook PST format which can be easily imported into any Outlook account.  

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