In Thunderbird: You can use 'ImportExportTools' addon extension for importing either mbox files (Importmbox file) or .eml individual emails (import messages).

If you can export emails as .eml files then they can be imported. Otherwise you need to use a converter...pst to mbox.

I've never used a converter, so cannot recommend any particular product. Most you may need to pay for the software, but I did find this: https://www.aid4mail.com/download-free-mbox-converter

Worth checking it out to see if it really is free.

Sorry, it would appear that the converter link converts mbox to eml etc not what you really need.

This sounds better: https://www.outlookfreeware.com/en/products/all/OutlookMessagesExportMBOX

Thanks every who is helped me!

I have tried this 'ImportExportTools' tool, unfortunately I was unable not to import all Mailbox data from my PST file to my Thunderbird account.

I was needed a solution to import, I have to buy a PST to MBOX Converter from this site: [] , it was amazing software that helped me to imported to my Thunderbird account.