Rated 1 out of 5 stars

Same problem as Mark Acosta.
Exported Mails from a .pst via Outlook Viewer to .eml files and tried to import them with your addon. It just imported the folder structure but not the mails itself.
Reverted Thunderbird to 60.9.0, used the old addon and it worked.
Not trying to sh*t on your hard work, thanks a lot for trying to port the addon.
Will edit the review when the problem is fixed.

This review is for a previous version of the add-on (4.0.2). 

Have you tried the 4.0.4 update? it should take care of both import and export issues. if it looks good it would be great update the review

Thanks for the issue report!
Unfortunately I got between unannounced deprecations with point provisions to TB.
I have a beta that addresses EML subfolder import. Prior 4.0.2 addressed attachment export.
I want to do some more regression testing then will submit. Any feedback great
I don't have Outlook currently so I export/reimport to test EML. GH beta pointer: