Need app to read EUDORA mail (that mailbox file format)

I was unable to successfully copy my 20 years of Eudora emails to Thunderbird. The process is difficult to follow & just seems to hang.

There must be a simple app that will allow me to open a Eudora mailbox folder, and select an email from an index list, and read the contents. Its just a "flat file" with a marker to separate each email. And maybe a separate toc (table of contents) file with the header data and a pointer to the location in the flat file.

And somebody please create the tag "Eudora"