.OST File Recovery

Have files been deleted due to a user’s error or software error? Have you formatted a disk by accident and need to know how to recover the files? Read our .OST file recovery guide for Windows, MacOS, Android and IOS in 2024.

OST File Recovery

What is a .OST file?

An OST file is a data file created by Microsoft Outlook (2005 or later), an email client and personal information manager. It is used to store a copy of mailbox information from an Office 365, Exchange, or Outlook.com account. OST files may contain email messages, contacts, tasks, calendar data, and other account information.

What Are Common Causes of ".OST" Files Lost or Failure?

There are several common causes of ".OST" files lost or failure:

  1. Synchronization issues: If there are synchronization problems between the Exchange server and the Outlook application, it can lead to OST file corruption or loss.
  2. Abrupt termination of Outlook: If Outlook is closed improperly or crashes unexpectedly, it can result in OST file corruption or loss.
  3. Virus or malware attacks: Malicious software can infect and damage the OST files, making them inaccessible or causing data loss.
  4. Oversized OST files: When the OST file exceeds its size limit, it can become prone to corruption or failure.
  5. Hardware or software issues: Problems with the hard drive, system crashes, or conflicts with other software applications can cause OST file loss or corruption.
  6. Accidental deletion: Users may accidentally delete the OST file or its contents, leading to data loss.
  7. Operating system issues: Issues with the operating system, such as system crashes or file system errors, can result in OST file failure.
  8. Network problems: Network interruptions or connectivity issues between the Outlook client and the Exchange server can cause OST file synchronization problems or corruption.
  9. Power outages: Unexpected power outages or improper shutdowns can cause OST file corruption or loss of data.
  10. Migration or upgrade issues: During the migration or upgrade of Outlook or Exchange server, there may be compatibility issues or errors that can lead to OST file failure or loss.

How to recover lost ".OST" files?

Sometimes while working with a computer, laptop or other stationary or mobile devices, you may encounter various bugs, freezes, hardware or software failures, even in spite of regular updates and junk cleaning. As a result, an important ".OST" file may be deleted.

Go to view
🧺 How to Recover Files and Folders After Sending Them to the Recycle Bin and Deleting? (Windows 11)

🧺 How to Recover Files and Folders After Sending Them to the Recycle Bin and Deleting? (Windows 11)

By no means should you think that the only way to recover a ".OST" file is always to create it once more.

Use programs for recovering ".OST" files if a file was lost after accidental or deliberate deleting, formatting the memory card or the internal storage, cleaning the storage device, after a virus attack or a system failure.

Programs to recover ".OST" files

Looking for a way to get files back? In cases when files were deleted and they cannot be restored by using standard operating system tools, use Hetman Partition Recovery.

Partition Recovery™ 4.9
The tool recovers data from any devices, regardless of the cause of data loss.

Follow the directions below:

  1. Download Hetman Partition Recovery, install and start the program.

  2. The program will automatically scan the computer and display all hard disks and removable drives connected to it, as well as physical and local disks.

    File Recovery Software
  3. Double-click on the disk from which you need to recover ".OST" files, and select analysis type.

    Hetman Partition Recovery - Analysis Type
  4. When the scanning is over, you will be shown the files for recovery.

    Hetman Partition Recovery - Files that Can be Restored
  5. To find a file you need, use the program’s interface to open the folder it was deleted from, or go to the folder "Content-Aware Analysis" and select the required file type.

    Hetman Partition Recovery - Deep Scan
  6. Select the files you have been looking for and click "Recovery".

    File Recovery Software - Files List for Recovery
  7. Choose one of the methods for saving the files and recover them.

    Saving recovered files in Hetman Partition Recovery

How to open file with ".OST" extension?

Looking for how to open a stereo outlook Offline Data File image file file?

Programs that open ".OST" files

Microsoft Outlook 2019 Microsoft Outlook 2019
Remo Convert OST to PST Remo Convert OST to PST
OEMailRecovery.com Outlook Recovery Toolbox OEMailRecovery.com Outlook Recovery Toolbox
4Team Corporation OST PST Viewer 4Team Corporation OST PST Viewer
Aryson OST Recovery Aryson OST Recovery

Additional Information

  • File type: Outlook Offline Data File

  • File extension: .OST

  • Developer: Microsoft

  • Category: Misc Files

  • Format: Binary


We will be happy to answer your questions!

Comments (1)

  • Hetman Software: Data Recovery
    Hetman Software: Data Recovery 18.12.2019 14:54 #
    Leave a comment if you have any questions about Recovering lost .OST files after deleting, cleaning or formatting!
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Vladimir Artiukh

Author: Vladimir Artiukh, Technical Writer

Vladimir Artiukh is a technical writer for Hetman Software, as well as the voice and face of their English-speaking YouTube channel, Hetman Software: Data Recovery for Windows. He handles tutorials, how-tos, and detailed reviews on how the company’s tools work with all kinds of data storage devices.

Oleg Afonin

Editor: Oleg Afonin, Technical Writer

Oleg Afonin is an expert in mobile forensics, data recovery and computer systems. He often attends large data security conferences, and writes several blogs for such resources as xaker.ru, Elcomsoft and Habr. In addition to his online activities, Oleg’s articles are also published in professional magazines. Also, Oleg Afonin is the co-author of a well-known book, Mobile Forensics - Advanced Investigative Strategies.


Questions and answers

  • What are some common reasons for encountering problems when opening .OST files and how can they be fixed?

    There are several common reasons for encountering problems when opening .OST files, and they can be fixed using the following methods:

    1. Corruption: OST files can get corrupted due to various reasons like power failures, abrupt system shutdowns, malware infections, etc. To fix this, you can use the built-in Inbox Repair Tool (scanpst.exe) provided by Microsoft Office. This tool scans and repairs the corrupted OST file.
    2. Synchronization Issues: If there are synchronization problems between the OST file and the Exchange Server, it can lead to errors while opening the file. To resolve this, you can try disabling the Cached Exchange Mode, deleting and re-creating the OST file, or repairing the Outlook profile.
    3. Large File Size: If the OST file exceeds its maximum size limit, it can cause issues while opening. You can try archiving or deleting unnecessary items from your mailbox to reduce the file size. Alternatively, you can convert the OST file to a PST file format using third-party tools and then open it in Outlook.
    4. Network Connectivity Problems: If there are network connectivity issues between the client and the Exchange Server, it can affect the opening of OST files. Ensure that you have a stable network connection and try opening the file again.
    5. Outlook Version Incompatibility: Sometimes, an older version of Outlook may not be compatible with a newer OST file format. In such cases, you can try updating your Outlook to the latest version or converting the OST file to a compatible format using third-party tools.
    6. Password-Protected OST Files: If the OST file is password-protected and you don't have the correct password, you won't be able to open it. Make sure you have the correct password or contact the person who set the password for assistance.

    In case none of the above methods work, it is recommended to seek professional help or contact Microsoft Support for further assistance.

  • What are some troubleshooting steps to resolve issues with opening .OST files in Microsoft Outlook?
    1. Restart Outlook: Sometimes, a simple restart can resolve the issue. Close Outlook completely and then reopen it to see if the .OST file opens without any problems.
    2. Check for file corruption: If the .OST file is corrupted, it can cause issues with opening. Use the Inbox Repair Tool (scanpst.exe) provided by Microsoft to scan and repair any corruption in the .OST file. The tool can be found in the Microsoft Office installation directory.
    3. Disable add-ins: Add-ins in Outlook can sometimes conflict with the opening of .OST files. Disable any third-party add-ins and then try opening the .OST file again. If it opens successfully, you can enable the add-ins one by one to identify the problematic one.
    4. Create a new Outlook profile: Sometimes, the Outlook profile itself can be the cause of the issue. Create a new profile and configure it with the necessary email accounts. Then, try opening the .OST file using the new profile.
    5. Check for sufficient disk space: Ensure that there is enough free disk space available on the drive where the .OST file is located. Lack of disk space can prevent the file from opening.
    6. Repair Office installation: If none of the above steps work, try repairing the Office installation. Go to the Control Panel, select "Programs and Features," find Microsoft Office in the list, and choose "Repair" or "Change" to repair the installation.
    7. Contact Microsoft Support: If the issue persists after trying all the troubleshooting steps, it may be necessary to contact Microsoft Support for further assistance. They can provide specific guidance based on the version of Outlook and any error messages encountered.
  • Are there any specialized software or tools available to help fix problems with opening .OST files?

    Yes, there are specialized software and tools available to help fix problems with opening .OST files. Some popular options include:

    1. Stellar OST to PST Converter: It is a reliable software that converts inaccessible OST files to PST format, allowing you to access your data in Outlook.
    2. SysTools OST Recovery: This tool helps in recovering corrupt or damaged OST files and converts them into PST, EML, MSG, or Office 365 format.
    3. Kernel for OST to PST Converter: It is a powerful tool that can repair and convert OST files to PST format, providing access to the data in Outlook.
    4. Aryson OST to PST Converter: This software converts OST files to PST, MSG, MBOX, EML, and other formats, enabling you to open and access the data.
    5. OST2PST Wizard: It is a simple yet effective tool to convert OST files to PST format, resolving issues with opening and accessing the data.

    Before using any software, it is recommended to research and choose a reliable tool that suits your specific requirements.

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