You can try KDETools PST to MBOX converter Software which is easy and smart solution. This PST converter is a program that can easily replace Eudora, Entourage, Opera, Spicebird, Thunderbird, Apple Mail, SeaMonkey, and others. There is no file size limit and users can convert large PST files to MBOX without any hassle. Users can take a preview of the content for free before the conversion process begins.

READ MORE:  https://www.kdetools.com/pst/mbox/