When a user uses MS Outlook in offline mode, all mailbox data is saved in the OST (Offline Storage Table) file format. For example, users may experience difficulties accessing OST data, or crucial files may become inaccessible to them. When attempting to open OST data, users may receive the error “OST is not an Outlook data file.” As a result, the user must correct the error and recover access to the critical data before the data is completely lost. The user is presented with a popup that displays the error and the information.

We’ll show you how to fix the “Outlook data file cannot be opened” error in this blog. Further, we’ll go over how to fix OST files and regain access to the OST database using both a manual and a third-party OST Recovery Tool.

Primary Reasons Behind OST Is Not An Outlook Data File error

The following reasons are given below why OST is not an Outlook data file error.:

  • The OST file may be corrupted or damaged.
  • Abrupt system shutdown or power failure while running Outlook.
  • Suddenly power off of Outlook may cause an OST file error.
  • A poor Internet connection may cause Sync failure with the Exchange server.
  • Some physical failures in the hard drive can also cause the OST file to be inaccessible.

Previously, we discussed various reasons why OST is not an Outlook data file error. Now we’ll look at how to resolve Outlook data file corruption manually.

Manual Methods To Resolve Outlook Data File Corruption

Users who are having problems with Outlook cannot open OST File, Outlook 2016 OST cannot be opened in Windows 10 can use the manual steps to resolve the problem. The manual procedure is time-consuming and does not provide a permanent answer. There’s also the possibility of human error, which could result in significant data loss. We will also discuss professional techniques as an alternative. To avoid data loss, make a backup of the OST data before beginning the manual process.

After the given reason, now we will discuss the manual methods to resolve Outlook data file corruption, which are listed below:-

  • Why Outlook Cannot Open OST File
  • Outlook Data File Cannot Be Found using Third-Party Utility

#Method 1:  Why Outlook Cannot Open OST File

  1. First, exit the Outlook. Move to the Control Panel and press the Mail button.
  2. In the Mail Setup dialog box, click on the Show Profiles button. Select your profile and choose properties.
  3. Now, choose the Exchange Account from the Mail option and press the Change button and, it enables Use Cached Exchange Mode.
  4. Go for more settings from the Advanced tab and then select offline folder file settings.
  5. Next, Pick the disable offline option and click on the Yes button.
  6. Go again to offline folder file settings, Press on OK button, next hit on the Yes button.
  7. From the Cached Exchange Mode settings, tick on the option of Use Cached Exchange Mode.
  8. After that, click on the Ok button, Go to Next, and then hit on the Finish button.
  9. At last, close the Account Settings and Mail Setup wizard.

As above, methods why Outlook cannot open OST files are discussed. If the user finds any difficulty to perform the manual method, we have a professional method of Outlook data file cannot be found.

Limitations of Manual Techniques Why Outlook Data File Cannot Be Accessed

The following Limitations are given below why Outlook data files cannot be accessed:

  • Inappropriate installation of Outlook application.
  • Outlook OST File Missing error.
  • Incapable to work on heavily corrupt OST files. It only fixes the issue of minor corruption.
  • If the corruption is not recovered in one go, then the tool can take two or more attempts to recover OST files, which takes a lot of time for the users.
  • When the recovery process is finished, the OST files are sometimes left with some inadequate sectors that make them inaccessible for future use.

Recently, We discussed the limitations of why Outlook data files cannot be accessed by using manual methods in the simple steps. Above we discussed that Outlook data files cannot be found using third-party software.

Professional Method of Outlook Data File Cannot Be Found

Here are various methods why Outlook cannot open OST files. It works competently to search where my OST File and helps to fix OST files, Outlook 2016 OST cannot be Opened. And, if you are searching for a tool that works effectively on your system to rename OST files, then third-party software is perfect.


In the end, as we tell you, there are multiple techniques to resolve Outlook data file corruption. To simplify the problem, we have introduced both manual and professional methods. As we discussed, the first manual methods with their limitations. After that, we introduced an automated technique recommended by IT professionals. I hope your issue regarding the Outlook data file cannot be accessed is fixed now.