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Summary: Microsoft Outlook users face OST file corruption issues. Causes include deletion, malware, sync failure, and more. Solutions involve profile management, disabling Compatibility Mode, and using a professional tool like Kernel for OST to PST

Microsoft Outlook is a widely utilized email client, catering not only to Windows users but also to Mac users through Outlook for Mac, offering streamlined email management.

While Microsoft Outlook offers numerous advantages, it’s not without its drawbacks. Among its millions of users, many encounter unexpected issues that can suddenly appear on their screens.

Microsoft operates various product and service-specific forums where users can submit their inquiries. A glance at the Office forums reveals a noticeable surge in user-reported issues and the impact they have on productivity.


Understand why OST file corrupts!

OST files, or Offline Storage Tables, serve as a local copy of the original mailbox hosted on the Exchange Server. This copy synchronizes at regular intervals, ensuring continuous access to the mailbox for the account owner, even when server connectivity is unavailable.

OST file corruption reasons

Several factors can lead to inaccessibility issues with Outlook OST emails, including:

  • One common cause of Outlook OST email inaccessibility is the deletion of file(s) or folder(s) from the Exchange folder.
  • Malware or virus attack.
  • Synchronization failure due to abnormal shutdown failure.
  • Outlook is crashing because of internal discrepancies.
  • Bad sectors error in the hard drive where the OST file is stored.
  • Changes in the internal structure of Outlook OST file.
  • Issues due to Add-ins are causing damage to the OST file.
Fix OST file corruption issue
  1. Remove silent (not in use) Outlook OST profiles:
  2. Open Outlook and click on File tab > Account Settings > Manage Profiles; click Show Profiles.
    From there you can select all the silent Outlook profiles and remove them.

    add and remove profile

  3. Make another copy of Outlook OST file; this will eliminate all the issues associated with the old OST file.
  4. In case if the error is not sorted even after going through the above steps then, create a new profile.
Error due to running in Compatibility Mode

In most cases, Compatibility Mode is not necessary for Outlook, regardless of the version, when running on Windows Vista, 7, 8, 8.1, or 10. Therefore, it is not recommended to use Compatibility Mode for applications specifically designed for the Windows operating system.

Here are some of the most common errors you may encounter when running Outlook in Compatibility Mode:

  • “Cannot open your default email folders. Information store could not be opened.”
  • “Cannot start Microsoft Outlook. Cannot open the Outlook Windows. The server is not available. Contact your administrator if this condition persists.”
  • “Cannot display the folder. File access is denied. You do not have the permission required to access the file C:\Users\username\localsettings\application\data\microsoft\outlook\outlook.ost”

Enabling Compatibility Mode for Outlook can lead to conflicts. Therefore, it is advisable to consider disabling it if you encounter any issues.

Disable Compatibility Mode on 64-bit Windows OS, follow the steps below:
  1. Navigate to the address: C:\Program Files(x86)\Microsoft Office\Office XX\Outlook.exe.
  2. Right-click on the application (exe), click on Properties and select the Compatibility tab.
  3. Uncheck the checkbox named Run this program in compatibility mode, click Apply; click Ok.

If the Compatibility tab is missing, follow steps below:

  • Click Start > search for Program Compatibility Troubleshooter.
  • Start the utility; click Next;
  • Select Outlook XX from the list of programs.
  • Follow the steps for disabling Compatibility Mode.
Use a professional tool

Utilizing a professional OST to PST conversion tool is the recommended approach for repairing and recovering OST file data, minimizing the risk of encountering complications. Not all users possess the technical expertise to address such issues, particularly when managing critical business emails with Outlook.

Kernel for OST to PST

Kernel for OST to PST is an advanced OST to PST converter tool specifically designed to address scenarios like the ones mentioned above.

ost to pst converter

This tool allows you to recreate and recover damaged OST files without the need to address the underlying issue first. It features an intuitive GUI for easy navigation and provides a user-friendly experience. Additionally, you have the capability to import multiple corrupt or damaged Outlook OST files simultaneously and repair them all in a single operation.


Identifying the right solution for the error you encounter in Microsoft Outlook can be challenging, given the variety of potential issues that can negatively impact a user’s productivity. We have outlined the most suitable methods to help you in such situations. In general, it is advisable to begin with the use of a professional tool to prevent data loss.

Kernel for OST to PST