here are some recent discussions around Eudora. I sort of got sick of helping folks with it over 100 versions ago when there was a functional importer from Eudora, but as the product has been discontinued for more than a decade no one could be bothered fixing the importer for Eudora when it broke years ago. So there is no importer anymore, you have to use an ago appropriate version of Thunderbird. Here are some recent discussion on Eudora from like minded individuals. https://support.mozilla.org/en-US/questions/1470910#answer-1684294 Then there is the official documentation instructions https://support.mozilla.org/en-US/kb/switching-thunderbird#w_importing-from-outlook-and-eudora Then there is https://support.mozilla.org/en-US/questions/1478773 That collectively should provide the information required. The most important being get an old copy of Thunderbird that actually knows what Eudora was and can import from it, the second being the version you import from must be installed and running. If you waited until it would not run, there is a high likelihood that the import will simply not work.