Recover emails from an OST file

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

You can use the OST PST Viewer (pstwalker.exe) to search for and recover emails from an Offline Outlook Data File (.ost). The OST PST Viewer can open orphaned, corrupted, encrypted, and password protected .ost files. Supported command line switches: export emails from an .ost file to .msg, .eml files or .pst file; find and recover hard deleted and orphaned items.

You might want to recover emails from an OST file in the following situations:

The reason for these errors and other problems in synchronizing might be a corrupted OST file. According to the articles above, Microsoft recommends that you delete your .ost file and that you let Outlook redownload the information from the server that is running Microsoft Exchange Server. After the mailbox is synchronized, test to see whether the issue still occurs.

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

In some cases, emails may not be recovered from the Exchange Server. An alternative to rebuild the OST file is to export the data to an Outlook Data File (.pst) or MSG File Format (.msg).

How to recover data from .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 PST - Outlook Data File as file format and All items in this folder and subfolders.
    Export options
  7. Select destination folder and click Ok.
  8. Wait for the export to finish.

Now you can find the recovered data from OST file in the destination .pst file.

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. You need PST Walker Business License in order to process the .ost file type.

Command line switches

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

pstwalker.exe [filename] [/E[:msg|umsg|eml] [/Name[:Id|EntryId|Subject]] [/PATH:folder] [/FullScan] [/HardDeleted] [/HardDeletedOnly]]

Specifies the .pst files to process. A filename mask can be applied, e.g. c:\source_folder\*.pst
Bulk extract messages to:
  • msg - .msg file format
  • umsg - unicode .msg file format
  • eml - .eml(rfc 822) file format
Naming style for the saved messages:
  • Id - incremental Id
  • EntryId - PR_ENTRYID (unique message identifier)
  • Subject - message subject
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

Updated on November 15, 2021

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See Also

How to use PST Walker

This guide explains how to open, find and extract emails from .pst files and .ost files with portable PST Viewer.

Convert OST to PST

You can use this guide to convert OST to PST file format, in case of data loss on the mail server, or when you need to recover a deleted, orphaned or inaccessible OST file.

Search multiple .pst and .ost files without Outlook

Boolean search, Excel-like filtering, instant search. Supports any .pst and .ost files: corrupted, orpah, archive, password protected and encrypted files. Export search results to numerous formats.

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.