use the import on the tools menu

Thanks Matt. However, my version of Thunderbird (version 102.14.0(64bit)) on my iMac desktop does not offer an option to import Outlook files or mbox files. When I select Tools, Import I get 4 options but nothing for Outlook or mbox. Is there a hidden selection that would allow that? Is Thunderbird version 102.14.0(64bit) a "bad" or "poor" version? Is there another version of Thunderbird that I can download on my iMac that would provide those options of Outlook or mbox?

Help/More Troubleshooting, Profile Folder, Show in Finder, close TB, copy the mbox file into Mail/Local Folders, restart TB and find the folder under Local Folders in the Folder Pane. The mbox should have no file extension like .mbox.

Thanks Matt. However, my version of Thunderbird (version 102.14.0(64bit)) on my iMac desktop does not offer an option to import Outlook files or mbox files. When I select Tools, Import I get 4 options but nothing for Outlook or mbox. Is there a hidden selection that would allow that? Is Thunderbird version 102.14.0(64bit) a "bad" or "poor" version? Is there another version of Thunderbird that I can download on my iMac that would provide those options of Outlook or mbox?

Outlook is only offered if Outlook is installed, and not the spacial MAC versions that are only sort of outlook. I don't think that mac offers the DDE connections to outlook that window does, so it may well not be available in a mac as outlook import works by actively asking the installed Outlook version about what is available to copy.

I was sure I had recently seen an import MBOX in import. It's absence I would have to consider a major oversight. However this addon will do it for you and much more. https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/?src=ss