To recover an Outlook PST file from a corrupt OST file, you need to convert the OST file into PST format. Since Outlook does not provide a direct method for this, using an OST to PST Converter is the most effective solution. These tools help extract emails, contacts, calendar entries, and other data from a damaged OST file and save them as a new PST file, which can then be imported into Outlook. Additionally, you can try restoring data using Outlook's built-in "Import/Export" feature if the OST file is accessible, but for corrupted files, a professional converter is the best option.