Outlook.OST Cannot Be Opened Error

Last updated: February 15th, 2021 at 01:10 pm

Searching for a solution to resolve the “Outlook.ost cannot be opened” error in Microsoft Outlook? Your work is done! In this article, you are going to discuss the best solution to easily resolve this error to regain your OST file database in Outlook.

Microsoft Outlook is an email client, available as a part of the Microsoft Office suite. Outlook creates OST file, to store the user’s mailboxes on his local machine while Outlook doesn’t have a viable connection with Exchange Server.

Get the straight-forward solution to Reapir all corruption errors from Outlook OST, backup OST file & Convert OST to PST with eSoftTools OST to PST Converter Software.


Sometimes, when a user launches Outlook on his computer, it shows an error like- outlook OST file cannot be opened. Before going to the process of fixing this error first let’s see “what are the reasons for getting this error in MS Outlook“.

Reasons for getting the “Outlook OST Cannot Be Opened” error:

Here are some reasons that cause this error to pop up on the screen.

  • The first reason behind this “outlook cannot open the OST file” error is the inappropriate or improper installation of the MS Outlook application. Any problem with installation will not allow the files to open correctly.
  • Abruptly or forcefully termination of MS Outlook when the OST file is in use.
  • Sometimes this problem comes due to the issues in synchronization between the OST file and Exchange server.
  • When the outlook is deleted from the computer and your OST file is left orphaned.
  • Virus or malware infection can cause corruption or mild damage to the OST files.
  • Oversizing is still an issue with OST files that causes an error i.e. “outlook OST cannot be opened“.

Have a look at each of the mentioned reasons, and see which one is causing an issue for you. Once getting all the reasons, now move to the part of the solution for these reasons.

Manual Methods to Fix “Outlook.ost cannot be opened” error:-

Method 1: End entire Outlook related processes

  • Close MS Outlook program.
  • Launch the Task Manager on your computer.
  • Go to the Processes tab.
  • Now, in the Processes tab, look for the processes Communicator, Sync, Outlook, or MAPI. If any of these processes found, select it and click on the End Process button.

Method 2: Disable Outlook Cached Exchange Mode

  • Close MS Outlook and go to the control panel.
  • Click on the Mail option and then select Email Accounts.
  • Under the Email Accounts, hit on the Email tab.
  • Now click on Exchange account and then hit on Change.
  • Uncheck the “Use Cached Exchange Mode” option under offline settings and hit Next to finish the process.

Method 3: Disable the Outlook Add-ins

To improve the functionality of Outlook most users use third-party add-ins. But faulty add-ins may sometimes create some trouble and it may also cause Outlook errors. Thus, disable the add-ins by launching Outlook in safe mode can be a solution to fix this error. Do this by just typing “outlook /safe” in the Run dialog box. Try “Save and Send” and if it works, a faulty add-in is the main reason behind the error. You can also start Outlook in safe mode by following the below-mentioned steps:

  • Go to the shortcut icon for Outlook.
  • Now, press and hold the CTRL key and double-click the application shortcut.
  • Click ‘Yes’ when a window prompt appears asking if you want to start the application in Safe Mode

Method 4: Repair OST file with ScanOST.exe

Microsoft Outlook offers an inbuilt ‘OST Integrity Checker’ tool also known as ScanOST.exe which helps to rectify minor corruption problems in OST files. Repairing Outlook OST file with ScanOST.exe can be a solution to fix “Outlook.ost cannot be opened” error.

Follow the below steps resolve OST error:-

  • Exit from MS Outlook and navigate to the directory on your system where Outlook has been installed. Now, navigate to the ScanOST.exe location and double-click on it to launch this utility.
  • The application will prompt you to select the OST file for repair. Click on the Browse button and select the OST file from its location.

    Note:- If you don’t know its exact location, you can find it by typing the following in the Run dialog:

  • Click on the “Begin Scan” option to automatically check and remove the errors in the OST file.

Limitations of manual methods

  • The manual methods are time-consuming.
  • It is a hard task for non-technical users as it requires some technical knowledge.
  • It doesn’t ensure security for data as well.
  • Not a 100% guaranteed solution to repair Outlook corruption errors

Automated Solution to Resolve Outlook.OST Cannot Be Opened Error

Doesn’t want to use any manual method to repair Outlook OST error, then you can use the automated tool to resolve this error. You can use eSoftTools OST Recovery Software that is an effective method to save the time of the user. It ensures data protection while fixing up the error that has been detected in your file Outlook.OST file.


The best benefit you get with this solution is that each & everything would be done by the company to fix the error that has got detected in your file with full safety as well as security while keeping your details & information safe with us.

This solution saves your time & provides you with the best solution so that you may run your file easily. So, you get quality service & on-time solutions to fix the errors that have got detected in your file.


By applying manual tricks there is a risk of data loss. If you wish to fix the error that has been detected in the file outlook.OST then makes sure you get in touch with the best service provider.

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