Since Outlook express isn't a Mozilla software or email program you will have to ask Outlook support for why it's not importing.

dalponteea said

I am virtually certain i was able to easily do this using the import tools on the version of thunderbird I had about a year ago. But Outlook Express is no longer an option when I open the import tool.

I will flag this thread and ask a moderator to move this to the Thunderbird support forum.

Moved to the Thunderbird support queue.

http://kb.mozillazine.org/Import_from_Outlook_Express

If you have OE and TB installed on the same computer, the import wizard may work with an older version such as 17. If you have the messages in eml format, they can be easily imported to TB with ImportExportTools or direct drag and drop. The kb article mentions other options such as using MailStore as an intermediary or various dbx converters.

Thanks for your response and the link. The email folders I have are in OE dbx file format. I tried to get them into eml format using Win Live Mail but could not get that to work either. I cannot install OE because I am on WIn 10 which I'm pretty sure does not support OE. So I tried to backup to a version of T-Bird that was about 1 year old... which would correlate to when I thought I had done this successfully before. I went to version 52.6.0 which was released in Jan 2018 I think. In that version OE is an option for the Import wiz and I was able to successfully import a ton of OE emails easily to local folders... even with OE not installed because as i said I am Win 10. So looks problem is solved. But interesting that the OE option disappeared on more recent versions. After importing everything I went back to latest T-bird and backed up my Profile to make sure I I won't have to do this again.