First of all, I have to admit that I'm a bit of a Luddite who loved Eudora and OS X Tiger and still uses a double G5 email for that computer died. I have all the Eudora data from the hard drive and found that my even older G4 still worked well, so I tried to open the data with Eudora on that computer but couldn't make it work. Everything on the old hard drive has been good, so it seems that data was not lost / damaged.
I therefore thought to import the data instead of Thunderbird using Eudora Mail Cleaner. All this runs 10.4.11 on a G4. I installed the current Thunderbird version and confirmed that it is working. I followed the Eudora Mail Cleaner instructions and confirmed that the email is displayed in the Thunderbird profiles folder in the library. But Thunderbird does not seem to recognize the folders or the imported messages.
If only they had kept Eudora going. I would never have used anything else.