How to convert OST to PST

OST to PST conversion lets you save Outlook mailbox data from an OST file in a PST file. The best method depends on whether you can access the mailbox in Outlook, need to recover an inaccessible or orphaned OST, or want to convert specific data rather than the entire file.

You can convert an OST to PST using Outlook or a dedicated desktop converter. For automation and batch processing, command-line tools can be used with PowerShell or other scripting methods. The methods differ in how they handle inaccessible OST files, selective conversion, and batch processing, so the right approach depends on your particular situation.

Which method should you use?

The best method depends on whether the OST file can be accessed through Outlook and how you want to process the data. Outlook can create a PST from an accessible OST, while dedicated converters can work directly with OST files and offer additional options for selecting, filtering, or processing mailbox data.

Important: Methods 2–4 can process the OST file independently of the original Outlook profile. However, Microsoft Outlook must be installed to create the resulting PST file.

Online OST to PST conversion

You can convert OST to PST online using a web-based converter. However, OST files and the resulting PST files are often large, so uploading and downloading them can take considerable time. Online converters typically process all data in the uploaded file, while a desktop OST to PST converter gives you more control over what to export.

Uploading the entire file to an online service may therefore expose more data than you intend to convert. For confidential or business email data, consider whether uploading the source file to a third-party server is appropriate for your needs.

Method 1 - Outlook

If the OST is accessible through the original Outlook profile, you can use Microsoft Outlook to create a PST file. In Cached Exchange Mode, Outlook exports only the data currently stored in the local cache. Exchange and Microsoft 365 accounts may be configured to synchronize only a limited period of mail, so the resulting PST may not contain the entire mailbox.

To include older data, make sure the required mailbox content is synchronized before exporting, or turn off Cached Exchange Mode where appropriate. See Microsoft's instructions for exporting email, contacts, and calendar to a PST file for the steps to create a PST file from Outlook.

Best for: OST files that are accessible through Outlook when you need to create a PST using Microsoft's built-in export functionality.

Method 2 - OST to PST Converter

Use the OST to PST Converter when you need to convert an entire OST file or a folder containing multiple OST files directly to PST.

1. Close Microsoft Outlook and any other applications that may be accessing your Outlook mailbox.
2. Download and run the OST to PST Converter on your computer.
   Download Toggle Dropdown

   • OST to PST Installer (.exe)
   • OST to PST Portable (.zip)
3. Browse to the OST file or folder containing the OST files you want to convert, and click Open.
4. Select the destination folder for the converted PST files.
   
5. Set the export parameters and click Run.
6. Wait for the conversion to complete.
   
7. Review the conversion summary and log for any issues or errors.

Method 3 - PST Walker

Use PST Walker when you need to select specific emails, folders, or other Outlook items from an OST file and export them to PST.

1. Close Microsoft Outlook and any other applications that may be accessing your Outlook mailbox.
2. Download and run PST Walker on your computer.
   Download Toggle Dropdown

   • PST Walker Installer (.exe)
   • PST Walker Portable (.zip)
3. Browse to the OST file you want to convert, and click Open.
4. Browse and preview the Outlook items, including email messages, calendar items, contacts, and tasks.
   
5. Select the items you want to export and go to File > Export.
6. Select PST - Outlook Data File as the file format and click OK.
   
7. Select Selected Messages, choose the destination folder, and customize the additional export settings if needed.
8. Click Run and wait for the export to complete.

Method 4 - Command-Line Conversion

PstScan Pro provides command-line functionality for OST to PST conversion and batch processing. The OST to PST Converter supports command-line conversion with the Technician License. Both can be run directly from Command Prompt or automated with PowerShell, Task Scheduler, or other scripting tools.

cd "C:\Program Files (x86)\PSTWalker Software\PstScanPro"
$OSTFiles = @("c:\a.ost", "c:\b.ost")
foreach ($OST in $OSTFiles){
   .\pstscanpro.exe convert pst -f "$OST" -p "D:\PST-Queries" --% -q:"from:(=bobbymoore@contoso.com OR ""bobby moore"")"
}

cd C:\Program Files (x86)\PSTWalker Software\PstScanPro
pstscanpro.exe convert pst -f c:\users\*.ost -p "D:\PST files" --srcfolders

What data is preserved when converting OST to PST

Converting an OST to a PST does not simply change the file extension. Instead, it extracts supported Outlook data (email, contacts, tasks, calendar items, and other Outlook data) into a new PST file. Exchange-specific metadata and local cache synchronization details are omitted, as they are not needed in a standalone PST.

• When OST to PST Converter exports email, contacts, and calendar data to a PST file, it creates a copy of the data. The original OST file remains unchanged, and you can continue to access the original data in the OST file.
• When emails are exported, their attachments are included in the resulting PST file.
• OST to PST Converter does not export certain metadata, such as folder properties (views, permissions, and AutoArchive settings), message rules, or blocked senders lists.

Are there any limits when converting from OST to PST?

There is no limit on the number of OST files that can be converted. Our OST to PST converters does not impose a limit on the size of individual OST files. However, some license plans include limits on batch conversion. Actual processing limits may depend on available system resources and the application used to open the resulting PST files.

Frequently Asked Questions