Outlook 2019 will not start. Missing .ost file’ – Some quick fixes

Megha Sharma
Megha Sharma linkedin | Updated On - December 13, 2022 |

Read time 7 minutes

Many Outlook errors are related to OST files. It happens in the latest Outlook version (2019) too. Our discussion would be about the situation where the user is not able to start or launch the Microsoft Outlook 2019 due to the “missing .ost file” error.

An Exchange account utilizes an Offline Outlook data file as a storage file on the system (where Outlook is installed) to keep a copy of the Exchange mailboxes. It allows users to access, read, and work on previously downloaded emails, contacts, etc. even without the server connection (offline). The server connection is required only to send emails and download new emails.

Note: This .ost file cannot be ported, but a new one can be created in another system just by configuring the Exchange account there.

Why is Outlook not able to locate the .ost file?

If you are dealing with the inaccessibility of Outlook data due to error “missing .ost file,” then first know why this happens. The most common reasons for this error are:

  • Network connection or Outlook configuration issues
  • Unexpected shut down of the system or the application
  • Hardware failures
  • The intervention of third-party add-ins
  • Recent Office updates
  • Corrupted OST file

The above issues are not the only reasons for the problem which you are facing. Still, you can troubleshoot the issue by trying different solutions.

Let us troubleshoot and fix the issue of “missing .ost file.”

Check the Network Connection/Configuration Settings

Verify that the server, as well as the network connection, don’t have any issues. Also, make sure that configuration settings are correct.

Check and Replace Hardware Connections

If the issue has arisen after any recent hardware attachment, then check for such external hardware and remove it if not vital to your system. If any hardware requirement is there, then check for its authenticity and replace it with the new one (in case it is damaged).

Remove/Disable faulty Outlook add-ins

Third-party add-ins can interfere with applications like Microsoft Outlook and its synchronization process. So, try to find and remove the faulty add-ins from your Outlook application.

To disable faulty add-ins in Outlook program, perform these steps in the given order.

  1. Run Outlook in safe mode using outlook.exe /safe in the Windows Run box.
  2. Run Outlook in safe mode

  3. Select the Outlook profile to launch the application further.
  4. If you see that the application is running fine in the Safe mode, then add-ins are faulty, you need to remove or disable it.
  5. On the Outlook application interface, move to File>Options>Add-ins.
  6. Move to the right panel of the Outlook interface and under View and manage Office Add-ins, select COM Add-ins against Manage option, and then click on Go option.
  7. COM Add-ins

  8. On the next dialogue box, unselect all the add-ins checkboxes and then click OK.
  9. unselect all the add-ins

  10. Exit the Microsoft Outlook application.
  11. Restart the Outlook 2019 application.

Note: If Outlook application starts at the end of the last step, then it can be concluded that one or more add-ins were responsible for the issue, which you can track by enabling add-ins one by one and restarting the application.

Un-install Recent Updates to the Office Program

We know that updates are introduced to add the latest features, services, bug fixes, etc. but some updates affect the program adversely.

It is advised to install the previous version of the program again if the Outlook error has occurred after the recent update. After the installation, rerun the Outlook application.

Repair Corrupt Outlook Data Files

As we stated, one of the reasons for this issue could be corruption in the .ost file. In that case, we should repair the corrupt OST file. We can do it on our own utilizing the utility scanPST.exe.

This application scans and repairs errors in both the Outlook Data Files (.ost and .pst). It can repair minor corruption errors in the files limited to size up to 2 GB only.

The default location of this utility is – C:\Program Files (x86)\Microsoft Office\root\Office16

And the default location of the Outlook data file is – C:\users\username\Documents\Outlook Files

  1. First, it is advised to take a backup of the Outlook data files as a precautionary measure. Then users can go to the default location and double-click on the scanPST.exe to launch it.
  2. In the opened application, click on Browse to add the .pst or the .ost file to scan for the errors. Click on Start.
  3. scan for the errors

  4. The scanning of the added Outlook data file will get started. After the scan completion, you can view the error and its details.
  5. Next, click on the Repair option to fix the errors found in your data file.
  6. fix the errors

  7. Exit the application once the repair is completed
Recreate OST File

Recreate OST file is another way to fix the issues with the Outlook application. The process of recreation of .ost file is like this.

  1. Close the Microsoft Outlook application.
  2. On the Control Panel of your system, click Mail option.
  3. Then on the Mail Set-up page, click on Show Profiles option.
  4. Select the Exchange account profile and click on Properties. Click on the Email Accounts tab.
  5. From the Email tab, select the Exchange account and click on the Change option.
  6. On the Change Account page, make sure that the Use Cached Exchange Mode option is selected. Then click on the More Settings option.
  7. Switch to the Advanced tab and click on the Offline Folder File Settings option.
  8. Move to the File section and enter the .ost file path. Click OK.
  9. Provide a different .ost file name when prompted and click OK.
  10. Finally, click on Finish and exit the Mail Set-up.
  11. Start the Outlook application now. This time a new .ost file with synchronized Exchange mailboxes will be created automatically.

We sincerely hope that these solutions will work for you, and you can now access Exchange mailboxes in Outlook with the help of .ost file.

If the methods given above fails, we would like you to try Kernel OST to PST Converter tool which can repair .ost files corrupted up to any extent. Also, it helps to recover specific data from .ost mailboxes to .pst file format. In this way, the data is always secure and can be imported to Outlook anytime. It is surely the best way to repair and recover .ost files data.

So, try this efficient and reliable OST to PST converter utility as your final solution.

Good Luck!


OST file errors are unexpected and can occur due to multiple reasons like network issues, faulty add-ins, hardware failures, unexpected shutdowns, corrupt OST and more. One such error is discussed thoroughly in this blog along with some manual solutions. A smart and reliable utility to recover .ost file data is also suggested.

Kernel for OST to PST