Recovering emails from an OST file

Compatibility: Outlook for Microsoft 365, Outlook 2021, Outlook 2019, Outlook 2016, Outlook 2013

For most types of accounts, such as IMAP, Microsoft 365, Exchange, and, an Offline Outlook Data File (.ost) is used to store a synchronized copy of your mailbox information on your local computer. In some situations, such as network outages or data corruption, you may need to recover emails from an OST file. In this article, we will discuss some methods to recover emails from an OST file.

Note: In Outlook 2013 and earlier versions, IMAP accounts used an Outlook Data File (.pst).

Rebuilding the OST file

In earlier versions of Outlook, Microsoft previously recommended using the Scanost.exe tool for errors that occur with your offline Outlook Data File (.ost). The Scanost.exe tool is no longer available starting in Outlook 2010. Microsoft now recommends deleting your offline Outlook Data File (.ost) and letting Outlook redownload the information from the server. You might want to rebuild the .ost file in the following situations:

The reason for these errors and other problems in synchronization might be corruption in the .ost file, and in some cases, emails may not be synchronized from the server. When all you have is an ost-file and you can't access your email account via Outlook at the moment anymore either, an alternative to rebuilding the .ost file is to extract the data.

Information: After deleting the .ost file, any items that are saved locally will be lost, such as Calendar, Contacts, Tasks, and any folders marked Local only. In this situation, we recommend backing up your existing .ost file.

Extracting data from the OST file

If you encounter Outlook connection issues or cannot rebuild your .ost file, there are several tools available that can help you recover data from an OST file. These tools can extract emails from .ost files without requiring Microsoft Outlook or a server account connection. They can help you recover important emails, contacts, tasks, and other data from your OST file and save it in various file formats for future use.

Exporting emails using OST PST Viewer

OST PST Viewer can open orphaned, corrupted, encrypted, and password-protected OST files. With this tool, you can export emails from an OST file to various file formats, including MSG, EML, and PST. Follow these steps to export emails from an OST file.

  1. Close Microsoft Outlook and all other mail-enabled applications that may use your Outlook mailbox.
  2. Download the OST PST Viewer, and run it on your computer.
  3. Browse the .ost file you want to recover and click Open.
  4. Select mailbox folder in All Folders pane, and preview all your items including messages, contacts, appointments, tasks, notes, and journal entries.
    Recover emails from an OST file
  5. Go to File > Export.
  6. Choose the file format for export and All items in this folder and subfolders.
    Export options
  7. Select the destination folder and click Ok.
  8. Wait for the export to finish.

Are there any limits when recover data from .ost file?

There is no limit on the number and size of the recovered OST files. You can convert unlimited folders or files as often as you like.

Recovering emails from an OST file using PowerShell

The program can bulk recover emails from an OST file in batch scripts using PowerShell, Task Scheduler, and other automation tools. To do this, use the command-line options of the product.

Note: Command line parameters are not available in the Home license.

   [-HardDeleted | -HardDeletedOnly]


The filename parameter specifies the .pst and .ost files to process. A filename mask can be applied, e.g. c:\users\*.pst

The E parameter specifies the file format for the saved messages. Exports to a file of the specified format:
  • msg - .msg file format
  • umsg - unicode .msg file format
  • eml - .eml(rfc 822) file format
  • pst - .pst Outlook Data File
  • mbox - .mbox Mozilla Thunderbird file format
The Name parameter specifies the naming style for the saved messages:
  • Id - incremental Id
  • EntryId - PR_ENTRYID (unique message identifier)
  • Subject - message subject
Specifies search query, see search keywords and boolean search operators

Specifies destination folder for bulk extracted messages

Extensive scan (to recover data from a damaged or a corrupted .pst, .ost files)

Find 'hard deleted' and 'orphaned' items

Export only 'hard deleted' and 'orphaned' items

Create .log file in ExportPath folder

Updated on May 04, 2023

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See Also

How to use PST Walker

This guide provides step-by-step instructions on how to use PST Walker. Learn how to navigate the interface, open and search for emails, extract attachments, and more.

Convert OST to PST

OST to PST Converter is a powerful tool that can convert multiple OST files to PST files. The tool can extract emails from .ost files without requiring Microsoft Outlook or a server account connection. This makes it a useful application in case of data loss, corruption, or inaccessibility of .ost files.

How to recover emails in Outlook for Microsoft 365

Learn how to troubleshoot missing data or emails in Outlook for Microsoft 365, and the steps to recover them if possible. Recover deleted messages in a user's mailbox in Exchange Online.