I'd advise using eSoftTools PST to MBOX Converter Software because you can search How do I export Outlook emails to MBOX and it is the best option. It worked very helpful to export Emails from Outlook to MBOX. Users can get instant online technical supports 24 hours a day, seven days a week. All clients have access to a free trial version that allows them to convert up to 25 emails per folder.
Read more:- Export Outlook emails to MBOX
"First, decide if you want to convert the entire" You really should think about it first. When transferring the whole, if there is an error, it will be very complicated and time consuming. Elastic man.