Using the third-party tool mbox viewer, you may quickly read and open mbox files. The eSoftTools MBOX viewer can easily open mbox files and convert MBOX files into MSG, EML, EMLX, HTML, NSF, Office365, Yahoo, and Gmail. This application is compatible with more than 20 email clients, including OperaMail, PocoMail, SeaMonkey, Eudora, AppleMail, and others. It may show all mbox mailboxes and folders in a live preview before converting them.
Read More:- Open mbox files with MBOX Viewer