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Outlook OST File Access is Denied : Troubleshoot The User Issue

Published By Nilesh Kumar
Debasish Pramanik
Approved By Debasish Pramanik
Published On January 25th, 2024
Reading Time 5 Minutes Reading
Category Outlook Tips

A set of rules is followed by every program because this ensures its effective functionality of it. There exists some standard set of rules, which is applicable to a program either when it is about Windows or Mac. Something like this also relates to the OST file. When an individual tries to open and access the content of a file, he/she encounters an error message i.e., “Outlook OST file access is denied”.

This interrupts the ongoing work of end-users in the Outlook program and hence, lead to problem in growth. Therefore, here we came with all tips and tricks to fix this common Outlook user’s query.

Measures to Fix ‘Outlook OST File Access is Denied’

Follow the below-mentioned instructions and try to fix the problem with it :

1. Launch Task Manager on the machine just by pressing Ctrl+Alt+Delete keys
2. Click on the Processes tab in the Windows Task Manager panel to proceed
3. Search for any one of the following applications or files. If encountered then, click on it and hit the End Process button

  1. Communicator
  2. Lync
  3. Ucmapi
  4. Outlook

This is just a general intro on what actually happens when the error statement ‘OST file access is denied’ occurs through programs. These applications will be associated with MS Outlook. There is a moment when this Windows Task Manager is examined and none of the related applications is found running at the backend, which prevents files from accessing. The upcoming section will be discussing some additional reasons, which are behind the occurrence of this problem and after this, one is going to get ideas to fix it.

Reason #1: Application Conflicts With Microsoft Outlook

Sometimes a condition arises where add-ons are unable to collaborate with the Outlook email client. This issue restricts access to the Outlook OST file. The compatibility issues with third-party applications could be the reason behind making the .ost files inaccessible for working.

Reason #2: OST File Opened in Web Console

There are scenarios where Outlook OST file is accessed via web console like Outlook Web access and now, someone on local machine tries to open the same file. If any changes are tried to make at either end, the error ‘OST file access is denied’ comes on the screen.

Reason #3: Unauthorized Access to OST File

One is very well-known from the fact that the OST file is specific to the MAPI protocol. So, when one tries to access the .ost file in the profile, which has not generated it, users will definitely face this problem.

Reason #4: Location of OST File is Relocated

If the location of the Outlook OST file changes in an unsystematic manner then, one is going to face an error. Since the file is server-dependent therefore, it is strongly recommended to end users that they should relocate the OST file location in a correct way. If all things go in the right way then, users are not going to encounter the ‘Outlook OST file access is denied error.

Note: The user can read this post to Convert OST to PST file easily. 

Workarounds to getting Rid Of the Problem

#1: Disable Add-ons or Integrated Tools

The measure to perform this is dependent upon the Microsoft Outlook edition. First, determine the version, which you are using on your PC, and then, proceed with illustrated steps :

MS Outlook 2007

  • Go to Tools to expand the menu with different options
  • Click on Trust Center >> Add-ins to disable the activated add-ins
  • Follow Steps (2) to (4), which are described in the next Outlook edition

MS Outlook 2010 / 2013 / 2016

  • Click on File >> Options >> Add-ins
  • Now, hit on the drop-down list of the Manage row and select the add-ins to be deactivated
  • Click on the Go button and do the modifications in a proper technical manner
  • Reflect all the changes made in Outlook by restarting the program

#2: Launch OST File in Single Console

Verify that the OST file is not opened by two different applications. If the file is already in use by one program then, you need to terminate it and then, use the same file with some other program where you want it to be.

#3: Open OST File in Original MAPI Profile

If the original Outlook profile is unavailable then, the only way left is to convert the OST file into PST format with a professional tool. For this, users need to opt for a program named OST Converter, which will help you to open OST files in Outlook. This will be making the file independent from the server and hence, fixing the problem.

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#4: Relocate the Outlook OST File Systematically

The OST file gets located on its default location when the Microsoft Outlook profile gets configured with the Exchange server. This is the reason why it is not easy to change the file location. Users need to follow the below-mentioned guidelines to relocate the OST file at the desired path :

  1. Choose the OST file, which is causing the error and create its copy
  2. Paste the copied file to a new location on the same machine
  3. Rename the previous file name with old.ost and once Outlook gets opened, it will be showing an error i.e., unable to access the OST file
  4. Navigate to the path where you have copied the .ost file and finally, the problem is resolved


There is no particular reason through which we can say that the ‘Outlook OST file access is denied’ error has occurred due to this. However, all possible reasons with solutions are described in this blog, which a user can use to fix the issue. If in case users are still facing any problems then, they can put a comment below. We will be researching their problem and providing an easy approach to resolve it.



By Nilesh Kumar

As a Chief Technical Writer, I know the technical issues faced by home and professional users. So, I decided to share all my knowledge via this blog. I love to help you with challenges while dealing with technical jargon.