How to Fix “OST File is in Use and Cannot be Accessed” Issue

OST to PST Converter /March 04, 2025

OST files are an integral part of Microsoft Outlook that enables users to work offline, make changes to the Outlook data, and then synchronize with the Exchange server whenever the connection is available. Nevertheless, some circumstances may cause the OST file to become unusable, and the user will receive the message “OST file is in use and cannot be accessed.”

This error commonly happens when Outlook cannot read or write on the OST file, and thus, users cannot access their emails, contacts, and other important information. By knowing the causes and applying the correct measures, users can easily return to their Outlook information and continue working.

Reasons for the “OST file is in Use and Cannot be Accessed” Issue

The issue “OST file is in use and cannot be accessed” is quite a popular one, and most often, it appears when the user is attempting to work with an Outlook data file. Here are some of the simple causes of this error:

  • The Outlook data file may be opened in another application or process on your computer or device.
  • The file may be opened in the read-only mode.
  • The file has some problems with permissions.
  • Multiple users running on the same OST file
  • OST file accessed unauthorised
  • Poor or bad internet connection
  • The file could be damaged as a result of a virus attack or any other cause

Methods to fix the “OST file is in use and cannot be accessed” issue

Users can opt to work with manual and automated workarounds since error messages that state that the OST file is in use and cannot be accessed are inevitable. These solutions are:

Method 1: Disable Cached Exchange Mode

This error can be due to several reasons, but one of the most general is that while your Exchange Server is running in Cached mode, your Outlook client is not. This can occur if you have recently transferred your emails to a new computer or upgraded your Outlook version. Here, we will explain how to turn off the Exchange cached mode to solve the error.

  1. Select the File tab in the MS Outlook.
  2. Go to Account Settings and then to Account Settings again.

    3. Account Settings

  3. Choose the Exchange account that needs to be modified and then click on the ‘Change’ button.
  4. Clear the check mark beside the “Use Cached Exchange Mode” option and click Next.

    5. Exchange account

  5. Click on Finish and then on Close.
  6. Close the Microsoft Outlook and re-open it to have the changes implemented.

Method 2:Recreate OST File

Given below are four simple steps to repair the OST file and resolve the error:

  1. Close all programs that are accessing Outlook data files. This error is usually displayed when an application seeks to open an Outlook data file currently opened by another program.
  2. Once you are done with all the applications, shut down your computer. This ensures that all the applications are closed and do not have any link to the Outlook data file.
  3. The next step is to delete the .ost file. To do this, you should go to the file’s location on your computer and remove it.
  4. The last action that needs to be done is to restart Outlook. After Outlook has been restarted, the new .ost file will be created & the error message should no longer appear

Method 3:End MS Outlook Processes

If you are receiving the message “OST file is in use and cannot be accessed”, it means there is a process still in use with the OST file. The following are the procedures to shut down MS Outlook and other processes to address the error:

  1. Open the Task Manager by doing the Ctrl+Alt+Delete shortcut.
  2. Go to the Processes page.
  3. Go to the Task Manager, look for outlook.exe or msimn.exe, and click on End Process for all of them.

    4. Task Manager

  4. Quit the Task Manager and try to open your OST file once again.

Method 4:Use GoldyTools OST to PST Converter

Goldytools OST to PST Converter is a professional tool that converts OST files to PST files in a few minutes. This tool also offers several features, including restoring deleted or permanently deleted items from an OST file, fixing damaged OST files, restoring emails, restoring password-protected OST files, converting encrypted OST files, and more. It also supports all versions of MS Outlook, including Outlook 2021 and Exchange Server 2019

Conclusion

The “OST file is in use and cannot be accessed” error can be quite annoying and sometimes can hinder your productivity, but the above methods can help you deal with the problem and carry on with your work without any more interruptions. If manual methods appear too complicated or take too much time to implement, Goldytools OST to PST Converter is the right solution to this problem. Get Goldytools now and ensure your Outlook data stays reachable and safe.

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