Try Cigati PST to MBOX Converter Software that can export your Outlook PST file into the MBOX file format without any hassle. The utility can convert the PST file into different file formats like MSG, PDF, EML, EMLX, HTML, CSV, DBX, etc. You can also migrate PST to various email clients such as Gmail, Yahoo, Office 365, Thunderbird, AOL, IMAP, etc.
For More Info Visit: Convert PST to MBOX Manually
I have tried this software for converting PST to MBOX file this KDETools PST to MBOX Converter Software. This converter provides updated feature and export attachments and emails to various file formats such as EML, EMLX, MSG, HTML, PDF, and etc. The ‘Message Filtering’ option helps the users to select PST items between two dates and start the conversion process.
VISIT HERE: https://www.kdetools.com/pst/mbox/