OST to PST Conversion

How to fix OST corruption with Outlook diagnostic and recovery tool?

OST file contains outlook mailbox in offline status when MS Outlook is disconnected from Exchange Server for temporary period. A single OST file stores only individual Outlook mailbox and saved on specific client server. OST file transfer Outlook mailbox information including changes back on the Exchange Server soon after connectivity is restored on the server.

Transfer of OST files to the Exchange Server is also known as OST synchronization. However, certain factors halt the OST synchronization process and consequently damage the OST files. These factors are virus and spyware intrusion, collapse of MS Office, damaged hard disk and many more. OST corruption is an event mostly disliked by system administrators and users as it make outlook mailboxes inaccessible on the Exchange Server. You will also lose all changes made in the OST file in the event of OST corruption. Microsoft Outlook is equipped with two powerful tools i.e., scanpst.exe and scanost.exe to diagnose and repair OST corruption issues.

Outlook diagnostic and recovery tool will help you when OST files show following error messages:

  • Outlook.OST is not an offline folder
  • Errors have been detected in the file xxxx.OST
  • Unable to expand folder

You’ll find both scanost and scanpst utilities in the local MS office folder of your computer. Scanpst.exe is also known as inbox repair tool that can repair both inaccessible PST and OST files of MS Outlook. You can start OST recovery process with inbox repair tool using below mentioned steps:

  1. Double click on Scanpst application

  2. Click “Browse” to select corrupt OST file from a computer drive

  3. Press “start” button to start scanning of corrupt or large OST file

  4. Click repair to fix the issues

Scanost utility is also known as OST integrity checker and more comprehensive tool to fix OST corruption. You can easily restore OST files having CRC, header corruption, 2 GB limitation and other minor issues with outlook inbuilt tools. After repairing of OST file by any Outlook recovery tool, you must connect the repaired OST file to the Exchange Server so that you can access your mailbox on the server. However, both scanost and scanpst tools are not capable of recovering exchange mailbox from the highly corrupt OST file. In that situation, a good mail backup will help you in recovering OST data.

In case, mail backup too is corrupt or unreadable, choose a third party OST to PST conversion software for recovery of OST files. OST to PST conversion software will extract OST data to PST format on a client server. A proficient OST to PST conversion tool supports every version of MS Exchange Server and MS Outlook. You shall be able to extract even deleted exchange mailboxes with OST to PST conversion software. All OST table recovered by the software can be viewed in a preview before you can save these in your computer drive or other location.


Microsoft outlook provide scanpst.exe and scanost.exe to fix corruption issues of OST files. Minor corruption OST corruption issues such as CRC issues, header damage and 2 GB limitation can be easily fixed with inbuilt recovery tool of Outlook. But severely damaged OST files are difficult to repair with Outlook recovery tool and therefore, you must recover your inaccessible mailbox using either a goof mail backup or OST to PST conversion tool.