The eSoftTools PST to MBOX Converter Software is a good option. Outlook PST to MBOX File Converter Software can simply convert Outlook PST files to MBOX files. It operates in a very straightforward and fast way. Email properties are preserved during the conversion of an Outlook PST file to an MBOX file. Without any difficulty, the software can convert PST files to Mbox files. You can download a demo version of this software from eSoftTools PST to MBOX Converter Software.
For more information:- Convert Outlook PST Files to MBOX Files