There are many situations where you may need to convert an OST file to a PST file. This could occur if the OST file becomes inaccessible due to issues like a sudden power cut, an Exchange server crash, or orphaning caused by changes in the Outlook profile. It may also be necessary when you want to open a different OST file in the same Outlook instance.

Unfortunately, there is no direct way to use an OST file in any version of Microsoft Outlook. To convert an OST file to PST, you will need third-party software. I recommend downloading and installing Goldytools Best OST to PST Converter for an efficient solution.

Key Features of Goldytools OST to PST Converter:

Quickly Convert OST to PST – Easily transform your OST files into PST format.
Convert to EML and MSG – Support for converting OST files to EML and MSG formats.
Compatibility with All Outlook Versions – Works with both 32-bit and 64-bit versions of Microsoft Outlook.
Full Windows OS Support – Compatible with all Windows operating systems.
The demo version allows you to preview the first 20 items from each mailbox folder, giving you a glimpse of what the full software can do.
https://www.goldytools.com/ost-to-pst-converter.php