MS Outlook is a desktop-based email client, which stores its complete data in two file format i.e., OST and PST. PST file can be opened easily without any problem but users cannot open OST file directly in MS Outlook due to some security features. There are several security issues, which denies to open OST file in MS Outlook. Some of those security issues are listed-below:

  • Encrypted OST file
  • Prevent misused of OST file
  • Safely stores emails

When users try to open OST file in MS Outlook, an error message “You are attempting to open a file of type ‘System File’ (.ost)" appear. To resolve this error, users have to convert their OST file to PST format.

How To Open OST File In Outlook?

To open Offline OST file in Microsoft Outlook, we have to convert OST file into PST format. There are two solutions to export OST to PST. First is the manual method and other is automated approach or a third party utility.

Manual Method

To export Exchange OST file to Outlook PST follow the below-mentioned steps:

  • Open Microsoft Outlook on your machine
  • Go to File and then select Export to a file. After that click on Next button
  • Now, select Personal File Folder (.pst) and then click on Next
  • Select the OST file, which you want to export and then check Include sub-folders
  • Now, browse the location where you want to save exported file and then click on Finish

Limitation Of Manual Method: The above manual method to convert OST to PST can be applicable only when a user is connected to the MS Exchange server.

Alternate Method

Users can use an alternative approach i.e. OST to PST converter tool to overcome the limitation of a manual approach. Follow the below-mentioned steps to export OST to PST using OST to PST converter tool:

  • Download and launch OST to PST converter tool on your machine
  • Then, click on Add file to add the OST file which you want to convert to PST
  • Now, select the items and then click on Export button or right click on selected items to choose Export option
  • An Export Options window appears. Select PST as destination type and then click on Browse to choose the destination location, where you want to save your Output PST file. After that click on Export button

Advantages Of OST To PST Converter

  • No need of Exchange Server environment to convert OST to PST
  • Recover deleted, damaged or corrupted OST file
  • Compatible with all versions of Windows OS
  • Microsoft Outlook installation is optional


MS Outlook does not allow users to open OST file due to some security features. When users try to open OST file, Outlook generates an error message. To resolve OST file not opening error, there is a need to convert OST file to PST. Therefore, the conversion of OST to PST can be done using a manual approach or using a third party tool i.e. OST to PST converter tool.


About Author

Diptesh Kumar Bhakat is proud to be the author of fastest growing tech blogs. He is a tech savvy. Mr. Diptesh is currently pursuing his B.Tech in Mechanical Engineering. He has a very close attachment with the tech world and loves to blog on his fav topics. He has also contributed to many regional dailies and authored guest posts on some of the leading tech blogs. You can reach him through Facebook, twitter, Google+ and linked-in.

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