Outlook OST File Access is Denied : Troubleshoot the User Issue

Admin | Published: 2021-02-02T12:05:00+00:00 | Outlook Tips

A set of rules is followed by every program because this ensures an effective functionality of it. There exists some standard set of rules, which is applicable on a program either when it is about Windows or Mac. Something like is this also relates to OST file of Microsoft Outlook. 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 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 machine just by pressing Ctrl+Alt+Delete keys
2. Click on the Processes tab in Windows Task Manager panel to proceed
3. Search for anyone of the following applications or files. If encountered then, click on it and hit End Process button

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

This is just a general intro on what actually happens when 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 backend, which prevents file 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 Outlook email client. This issue restricts accessing of Outlook OST file. The compatibility issues with third-party applications could be the reason behind making .ost file 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 made at the 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 OST file is specific with MAPI protocol. So, when one tries to access .ost file in the profile, which have not generated it, users will definitely face this problem.

Reason #4 : Location of OST File is Relocated

If the location of 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 OST file location in a correct way. If all things go in a right way then, users are not going to encounter ‘Outlook OST file access is denied’ error.

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

Workarounds to Get Rid Off 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
1) Go to Tools to expand the menu with different options
2) Click on Trust Center >> Add-ins to disable the activated add-ins
3) Follow Step (2) to (4), which are described in the next Outlook edition

MS Outlook 2010 / 2013 / 2016
1) Click on File >> Options >> Add-ins
2) Now, hit on the drop-down list of Manage row and select the add-ins to be deactivated
3) Click on the Go button and do the modifications in a proper technical manner
4) 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 application. 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 OST file into PST format with Outlook OST to PST Converter Application. For this, users need to opt for a program named as OST Converter, which move all the OST mailboxes to PST format. This will be making 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 below-mentioned guidelines to relocate OST file at the desired path :

1. Choose the OST file, which is causing 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 OST file
4. Navigate to the path where you have copied .ost file and finally, the problem is resolved


There is no particular reason through which we can say that ‘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 problem then, they can put a comment below. We will be researching upon their problem and provide an easy approach to resolve it.