I am not experineced in importing Outlook, but what you state is true. I do have some info on converting PST to MBOX, as I presume that is your primary concern.

This site, listed below, is FREE, but i a two-step process. To my knowledge, this is the only FREE service to make the transition to MBOX from PST. I believe it works only on Windows. Good luck. Please let me know how it goes, so I can advise other. Thank you.

https://www.mailstore.com/en/products/mailstore-home/ FREE import pst files and then export to mbox and then import to thunderbird https://support.mozilla.org/en-US/questions/1394487

Hi David, thanks for your reply. I have downloaded and installed Mailstore on my Windows system and archived one of my outlook pst files into .eml format. That resulted in a file that I shared with the Linux system. The archive contained the same directory structure as the source pst file. On Linux Thunderbird copy I created a new folder and imported the windows pst archive to that new folder.. That was partly successful. Some of the (sub)folders didn't import, while there were msgs (emails) in the source folder. The source pst folder structure itself was correctly copied to Thunderbird, but with some empty folders. There are log messages produced for the msgs that are are not imported. They don't mean much to me, but I will research and retry further. I will keep you informed.

WimV

Thanks for the feedback, as I regularly see requests to import PST to mbox. :)

There are commercial tools which can read .pst files.