If you want to extract emails from an OST file or have more control and flexibility over the extraction process or if you don't have access to the original Outlook profile, you can use third-party OST to PST conversion tools. Several reputable software applications are available for this purpose. The OST Converter tool allows you to convert the entire OST file into a PST file, and from there, you can easily extract emails using Microsoft Outlook. Refer: https://www.sametools.com/convert/ost/