View Contents Of Ost File

Learning has never been so easy! Summary: In this guide, you will learn about some free methods and workarounds to view OST file in Microsoft Outlook. These methods and workarounds will help you to open and view the default OST file in another Outlook profile.

Further, it discusses steps to convert and view inaccessible, damaged, or orphaned OST file by using an OST converter software. MS Outlook creates two different data files based on the type of email account. It creates a Personal Storage Table or PST file for POP accounts and Outlook Storage Table or OST for IMAP and MAPI-based email accounts, such as Exchange.

OST stores a local copy of mailbox items that are stored on the Exchange server, such as emails, attachments, contacts, tasks, notes, calendars, public folders, etc. It allows Outlook users to access their emails even when the system is disconnected from Exchange or offline.

By default, the OST file is encrypted with the MAPIEntryID GUID encryption key.

4 Steps total

OST is created and encrypted when a user configures or adds the IMAP or Exchange account in Outlook. This encryption key is saved on the server and local system’s registry file.


Thus, to access or view an OST file and its content by using Microsoft Outlook, you need to authenticate with valid user profile credentials. NOTE: If the account is removed from the server, the authentication may fail. In such a case, you can’t open or view OST by using Microsoft Outlook. And such OST files that belong to a deactivated or deleted IMAP or Exchange account are often referred to as Orphaned OSTs.

However, you can open and view any inaccessible, orphaned, downloaded, or copied OST file directly without any authentication by using an OST to PST converter software, such as Stellar Converter for OST.

Converting to PST format – the only solution

  • Below we have discussed different methods to open, view, and read OST file and mailbox items by using Microsoft Outlook.
  • If the current OST file does not open or an error, such as “The file xxx.ost is not an Outlook data file (.ost)”, is displayed, it indicates damage to the OST file.
  • In such cases, you can recreate the OST file and then view it in Microsoft Outlook.
  • The steps to recreate OST are as follows,. - Close Outlook and open Control Panel- Double-click on Mail.
  • This will recreate the OST file next time you open Outlook. This works for MS Outlook 2019, 2016, 2013, and 2010.
  • Alternatively, you can navigate to the OST file location and then rename its extension with .bak.
  • The steps are as follows,.

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  • - Navigate to the default location where OST is saved by OutlookC:\Users\USERNAME\AppData\Local\Microsoft\Outlook\- Right-click on the OST file and choose ‘Rename’, and then rename the file to anything.

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You may also edit the file extension to .bak- Alternatively, you can move the OST file to a different folder- Once done, open Outlook. You may need to sign in again - This creates a new OST file that you can open and view in Microsoft Outlook.

NOTE: This works only if your profile is active but the local OST file becomes inaccessible. If your account is removed from the server, this method won’t work and you will have to convert the inaccessible OST file to PST by using an OST to PST converter software discussed in Method 3 and Method 4.

Wrapping it up

  • Xst Reader is an open-source OST and PST file viewer tool.
  • It does not require Outlook installation to view the OST file.
  • However, it requires .NET Framework 4 to work on Windows.
  • To install and use it for viewing OST and PST files, follow these steps,.
  • - Download the source code of the Xst Reader project and install Visual Studio release- Extract the source code on your system and then double-click on XstReader.sln file in the root folder to open the project in Visual Studio- In Visual Studio, click on Build and then choose ‘Build’ or ‘Build Solution’ to compile the Xst Reader project files and components- Now run the build from Visual Studio and use it for viewing the OST fileYou may also download the XstReader.exe file and open it on Windows PC to view OST or PST files.
  • To download, visit the release page and download the latest file.

Method 3: Use OST to PST Converter Software

  • Then follow these steps,- Extract the folder and then run XstReader.exe- Click ‘Open’ and select the OST file- This will open the OST file for viewing.
  • Additionally, you may export the emails to HTML or rich text format.
  • Download the tool,

3. Stellar Converter for OST

software enables you to scan OST, preview the mails, find particular mails, and save them as EML, RTF, MSG, PDF or HTML formats. It also allows you to open and view inaccessible OST files. The steps are as follows, . Download, install and run Free OST Viewer tool2. Browse and select the OST file you want to view without Outlook3.

The software scans and displays all mail items, such as emails, attachments, contacts, notes, etc.4. To save emails and mailbox items, right-click and choose the desired format to save the mail items at your desired location .

Method 1: Use Outlook Archive Feature

  • Read more:
  • If the user account or profile is deleted from the Exchange server, OST enters into the Orphaned stage.
  • In such a case, you can’t access or view the Outlook OST file. To view orphaned and inaccessible files by using Microsoft Outlook, you can use an advanced OST to PST Converter software, such as Stellar Converter for OST.
  • With the help of this software, you can view or convert the downloaded, copied, inaccessible, or orphaned OST file into PST.
  • After conversion, you can open the PST file in Microsoft Outlook and view the mail items in any Outlook, Exchange, or Office 365 account.
  • Follow the link to Install & Free download the tool:
  • As OST file is encrypted by default, you can open and view the OST by using Microsoft Outlook via associated Outlook profile only.
  • One can’t view an inaccessible, damaged, orphaned, or OST file that belongs to a different profile on another Outlook profile or PC.
  • However, there are workarounds to view the mailbox items stored in the OST file by using a different Microsoft Outlook profile or account.

Method 2: Drag and Drop Mailbox Items

  • You can either use free OST Viewer tool or an OST to PST converter software to view and convert OST to Outlook readable/importable PST format.

4. SysTools OST Viewer

After conversion, you can open and view the exported PST file that contains OST mailbox data in any Microsoft Outlook. An OST to PST software also helps you convert an inaccessible or orphaned OST file to PST format in a few clicks.


  • Published: Oct 22, 2020 · Last Updated: Oct 04, 2021 . Adom (Aryson Technologies) Feb 16, 2021 at 08:20am .
  • You can view OST file without MS Outlook using Aryson OST Viewer tool.
  • Our engineers have analyzed the content of OST (source) and PST (destination) files.
  • The analysis revealed the types of data that are not carried over to the PST file after OST file conversion:.
  • old versions of messages, contacts, files and other objects.
  • removed objects. blocks of data from earlier versions of messages, contacts, files and other objects.


  • It is impossible to use these blocks to fully recreate the original object, which is why they can be treated as junk.
  • In other words, when you remove or modify a message, contact, reminder or meeting, the object is only marked as removed, but is not removed physically and remains in the OST file.

5. Aryson OST Viewer

The new version of the object is written to a newly allocated space, but the old version remains in the OST file as well. If Outlook is in active use, the size of the OST file can grow quite significantly, while the actual size of data in the file remains the same.


  • In order to optimize disk space consumption and remove old elements, you need to configure the AutoArchive feature in Microsoft Outlook.
  • search for and reading of old versions of documents is used by attackers for stealing users’ confidential information;.
  • search for and reading of deleted and old versions of documents is used by police authorities to collect compromising information (Forensic Mode);.
  • Recovery Toolbox for Outlook enables the user to search for data deleted from an OST/PST file and save it to the disk.
  • Summary: Outlook OST file becomes prone to corruption if it exceeds its prescribed size limit.


  • In such a case, it becomes difficult to access it through Outlook to view OST file data.


So how can users extract their valuable data stored inside inaccessible OST files through Outlook? Let us try to find out. When Outlook is used with Cached Mode On, all the data stored within the Microsoft Exchange mail account is saved on the local system for offline access.

This offline replica of the Exchange account data is known as Offline Storage Table file or OST file. OST files enable the users to work on their mailboxes in offline mode, even if the connectivity to Exchange Server is temporarily unavailable. Once connectivity is restored, all changes made to the mailboxes are synchronized with the online accounts Despite being a highly efficient email client, Outlook often faces issues because of problems with OST files.

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