If you search on the web for easiest way to convert MBOX file to PST then you will find numerous options. When I had faced this problem I used Bitacube MBOX to PST Converter. This tool provided me an advanced mechanism to convert multiple & huge MBOX file to PST format with maintaining all folders structure, mail properties, attachments, etc.
The software supports all MBOX/ MBX/ MBS based email client data, such as - Apple Mail, Entourage, Eudora, Postbox, Netscape, PocoMail, Thunderbird, Spicebird, Opera, PowerMail, Claws Mail, Evolution, SeaMonkey, Sylpheed, Mulberry, GyazMail, Gnu, Sparrow, The Bat!, WebMail, etc and transfer into PST file format.
Read More: https://www.bitacube.com/mbox-to-pst...converter.html