I am going to share a professional tool because the manual way is too risky and lengthy. While you can use the solution to export PST files into MBOX and EML file formats without any technical hassle.
You can check out the MailsDaddy PST file converter tool to convert and open PST files into Thunderbird, Windows Live Mail, Outlook Express, etc. This is the best exporting option for all levels of users.
Download or install MailsDaddy PST Converter > Launch the program and click on Add file.
Browse your PST file to add a mailbox into the software then OK.
Preview of emails is optional > Right-click on the mail to save it as MSG, RTF, EML, HTML, or MHTML. Otherwise, Tab on Export to convert PST files.
In the new window > Choose any option between Export all folders or Export Selective folder as per your requirement.
*Note: In the free Demo version users cannot export selective folders.
You're all done. It will take some time according to the file size and provide your data at the destination point.