OST File Won’t Open in MS Outlook 2016 – Error Fixed

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OST Files; How they help?

OST is an offline file folder present in Microsoft Outlook. The offline folder allows users to work on their messages and mail the data offline, even when access or connection to the mail server is not there. A clone or replica of all your mail messages and data in the exchange server mailbox is saved on your local computer automatically, as an OST file. So, when your internet connection gets disrupted, you can still access the local copy of emails and data in your outlook and work on them. Once the internet connection is re-established, or restoration of access to mail server happens, the messages and the data items get automatically synced. Generally, the IMAP accounts, exchange accounts, Office 365 accounts use this offline outlook data file (.ost) to store a cache of the data from your Microsoft outlook.

OUTLOOK 2016 WON’T OPEN OST File – A Frequent Issue

Think of a situation where you had written a mail of all the business proceedings and attached vital data to the mail and suddenly your internet connection gets disrupted. You would be relaxed that all such information is stored as a cached copy in OST file. Now the next time, you are unable to open the file on your outlook 2016.  You see an error message that “OST file cannot be opened”.

It would be a precarious situation, right? Not only you, but many people from all walks of life and using MS Outlook, frequently complain that Microsoft Outlook 2016 won’t open OST files on their system.

Well, there are many reasons for such technical disability. I have jotted down some of them below

  • You have not configured your email account, according to Outlook,
  • The Ost files get stored on a faulty section of the hard drive, making it inaccessible and corrupt.
  • The automatic synchronization between the OST file and the exchange server may have been abrupt, creating OST file error.
  • The abrupt closure of your MS outlook account owing to power failure may have corrupted the file.
  • Any malware application may have corrupted your file making it inaccessible.

Outlook won’t open OST files; Let’s recover the files

Don’t worry. It’s not time to hit the panic button or mourn the loss of your data, if you can’t open your OST files. Yes, we know, you must be thinking that your MS Outlook won’t open your crucial business deals file and I am asking you to cool off. This is because there are some systematic steps and validated ways through which you can recover your files in minutes. You just need to follow some of the methods of file recovery mentioned below.

Close the MS Outlook, other processes and then reopen outlook.

  • Open the task manager using Ctrl+Alt+ delete
  • Click on the processes


  • Select the MS outlook and forcefully end the process by pressing the END TASK.
  • If you find other processes or programs like UCMAPI.exe, Lync or Communicator, end these processes too.

Then again reopen the MS Outlook and try to open the OST file. It sometimes happens that some processes or applications running in the computer system may stop the OST file from opening. Moreover, sometimes the MS outlook getting hanged or unresponsive may create the OST file opening problem. Ending the MS Outlook process, along with the other processes mentioned above and then restarting MS Outlook again may solve the problem

Use Professional OST to PST Converter tool to fix “OST File Won’t Open in Outlook” Error

This method is a sure shot recovery method for orphan OST files. So one can directly convert OST file format to PST file format using a reliable OST to PST Converter software. Once data is migrated and converted, you can easily import the data in PST format in your Outlook easily. The tool has the capability to recover and convert all the mailbox items such as attachments, contacts, emails, notes, journals, calendars, etc. to Outlook PST and several other formats.

After converting into PST file format, you need to follow certain steps mentioned below.

  1. Open Outlook in offline mode
  2. Go to File menuOpen Export Import/Export and click it
  3. The import/export wizard appears
  4. Click on the Export option for the Outlook PST file
  5. Select the folder which contains your required data and click on the Next button
  6. Save the data on your system.

OST File Viewer Tool – Another Free Tool to view Inaccessible OST files

DRS OST file viewer tools can be used for viewing any OST file even if the file is corrupted or protected with passwords. The OST file viewer is bit god-send as it can help you view OST files without the installation of MS outlook, and works in all versions of Windows.


These three methods can be handy in order to resolve “OST File Won’t Open in Outlook” issue in Outlook 2016. However, choosing a professional OST to PST Converter software is an ideal option to fix this issue.

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