[Solved] – Can’t Open OST File in Outlook: Error in Microsoft Outlook

Admin | Cloud Backup Email Conversion Software | 4 minutes read | Last updated on February 8th, 2023,

Are you searching for the solution to fix the problem of OST file cannot be opened in Microsoft Outlook? Not to bother, we are here to resolve the issue related to OST file. In this blog, we are trying to provide an accurate solution to users by which, a user can easily access their OST data in Microsoft Outlook.

About OST and PST File Formats

Before continuing further, a user must need to know about the MS Outlook and their file formats. Microsoft Outlook is the commonly used email client application across the world in the organizations by the technical users. Outlook provides two file formats i.e. OST and PST. OST is usually known as Offline Storage Table. Generally, it is created when the connection between MS Exchange and the Microsoft Outlook account is established. It allows the user to work in an offline mode too by utilizing cached data. However, PST is a Personal Storage Table that simply stores the whole data items of MS Outlook in it. It stores all email messages, contacts, notes, tasks, attachments, calendar, and more.

Commonly Asking Errors Query of OST Files


Most users are stuck in these type of queries where they are looking for solutions related to their OST file errors. I have searched and analyzed the most searchable queries by which users are looking for an accurate solution. Here are some of the commonly asking queries which are searched on Google are described below:

  • The file username .ost is in use and can’t be accessed
  • The File username .ost cannot be opened
  • Outlook cannot start
  • The set of folders cannot be opened
  • Cannot open Outlook window

We are here to talk over about the solution for all these types of errors of OST files. I hope the solution for all these errors is the use for you all. This method makes lots of smiles on the user’s face.

What is the Perfect Solution to Resolve OST File Error?


There are a number of technical errors are occurred which guide to the corruption of OST files in Outlook, then the user receives the various types of technical errors. So, users are tried to look for the different methods for their queries. They are searching for the solution for how to deal with such type of issues. It is better to opt the third party application i.e. OST to PST Converter, which can simply allow users to export OST file in Outlook PST format and easily access their OST data in MS Outlook. It is a reliable move for users to import and transfer OST data into Microsoft Outlook.

Default Location of OST File


To export the OST file into PST file format, it is important to open the OST file from the defaulting location of the system and open it by the MS Outlook. It can be simple to find out your OST file in the system by finding the following file location:

C:\User\user name\AppData\Local\Microsoft\user name\username.ost

If a user tries to access OST file in MS Outlook, then the email client application gives an error.

“The file C:\User\user name\AppData\Local\Microsoft\user name\username.ost is in use and cannot be opened.”

Fixed Solution to Come Out from OST Error


If you searching for the manual method, firstly, the user has to take a backup of OST file. Then, if a user gets the above-discussed error, then try to restart your system. A user needs to follow the complete step by step guide:-

  1. Right, click on Taskbar >> Choose Task Manager.
  2. Now click on Processes
  3. Try to find out searching like “Communicator”, “Lync”, “ucmapi”, or “Outlook”. If you find any one of them, then choose it and click on “End Task”.

Fix Part 2:

  1. Now close your MS Outlook.
  2. Open Control Panel >> choose Mail >> Email Accounts.
  3. Select email address that shows a username .ost error and select Change.
  4. The, uncheck “Use Cached Exchange Mode”.
  5. After that final step is to press on Next and then Finish.

Now reinstall your MS Outlook to check the error are fixed successfully. If no one of the manual processes is working great, then the user needs to go with the third party tool that is recommended by the technical experts. It provides the number of advanced functionality to users by which they can smartly access their OST data again. This application easily allows the user to come out from all these numerous technical error conditions.

Try this OST file Conversion to PST software, it will quickly resolve your error.

I hope it will helpful for you.

Open OST File in Outlook