“The file XXX.ost, Outlook.ost is in use and cannot be accessed error” – [SOLVED]

Admin | Email Conversion File Repair How to's Outlook Software Technology | 4 minutes read | Last updated on February 8th, 2023,

Both MS Outlook and Exchange Server are popularly used apps. Number of users using Microsoft Outlook are familiar with .ost file type. It also stands for Offline Storage Table that stores mailbox items such as emails, contacts, calendar etc. when working in Outlook offline that has configuration with Exchange Server.

At times, users face an error i.e. Outlook.ost file or the file XXX.ost is in use and cannot be accessed; close any application that is using the file. It means that OST file you trying to access is already in use by another program or application. There are some similar issues, which one can observe when retrieving OST file.

The file XXX.ost is in use and cannot be accessed

Cannot open Outlook file is in use

ost file is in use and cannot be accessed

Outlook file in use by other application

The file cannot be accessed Outlook OST

Outlook OST cannot be opened

.ost cannot be accessed

Outlook 2016 cannot open OST file

Reasons Behind the Error “OST is in Use and Cannot be Accessed”

The reasons of such errors can be the OST accessibility by multiple users or same application at the same time. Some main reasons are listed below:

• Slow internet connectivity
• OST file synchronization on local machine with MS Exchange Server mailbox
• Runtime conflict of multiple different programs with Outlook email client
• Accessing same .ost file by multiple users or application at same time

How do you fix Outlook Data File (.ost) cannot be accessed error?

After knowing how to detect an error and finding the reasons behind such issues, the next step is to try to resolve these errors. For this, we have explained four approaches in the further section that can help to understand how to fix default.ost in use and cannot be accessed error.

Solution 1. Close Outlook App and Exit from all Outlook Processes

This is first solution that prove helpful to fix above-mentioned errors. Follow the steps carefully and perform the task:

1. First, exit Microsoft Outlook email client.
2. Go to task bar, right-click on it and select Task Manager.
3. Navigate to Processes tab and click on it.
4. Search “Communicator”, “Lync”, “ucmapi” or “Outlook”. If it is displayed, select End task button.

Solution 2. Disable Cached Exchange Mode

This is second method for fixing the error. In the solution, one need to disable the option of Cache Exchange Mode by implementing the following steps:

1. Close Microsoft Outlook application.
2. Open Control Panel and go to Mail button.
3. Click Email Accounts button and select Email tab.
4. Choose Email Address and hit Change.
5. Deselect the option of Use Cache Exchanged Mode, click Next and hit Finish.

Solution 3. Run Inbuilt Repair Tool

This is the third solution that users can apply to fix the issue of inaccessible OST file. Follow the steps and run ScanOST.exe app.

1. Close Microsoft Outlook email client.
2. Run ScanOST.exe.
3. Select Mailbox >> click Repair Errors >> Hit Begin Scan.
4. A process will take few minutes to scan hierarchy and fix issues.

Solution 4. OST Converter to Backup OST files to PST

If none of the above methods works, try to solve the issue of “Outlook.ost file is in use and cannot be accessed error” with OST Converter app. A direct and cost-effective utility that allows to backup unlimited OST files into PST with emails, contacts and calendar. Instead of waiting for any mishappening, take backup of OST data into PST file that can be opened and viewed anywhere without configuration of Exchange Server. You can also move these files to new system and analyse OST data without restriction. Besides PST format, there are many other desktop and cloud apps that you can use accordingly for the same. Follow the steps and check how to access inaccessible OST file:

Step 1. Download and run software on Windows OS system.

Step 2. Go to Select File(s) and choose Add Files, Add Folders or Load Outlook Profiles option to load .ost files for conversion.

Step 3. The tool will start the scanning and list all the associated files with checkboxes on left side of the software pane.

Step 4. Navigate to Saving Options and choose desired file type/cloud account to save Outlook.ost data.

Step 5. Click on Convert to start the process. After process is finished, an alert message will appear on the screen “Conversion Completed Successfully”. Click OK to exit.

Wrap Up

The segment has discussed multiple solutions to solve the error of “the file XXX.ost is in use and cannot be accessed”. A user can use the required method and fix the issue without facing any trouble. If in case, any of the above given method fails, go for third party app, which is reliable, and secure to use. Even, the non-technical users can use it to solve .ost cannot be accessed error.