Eudora is once again free.
I used a free edition of Eudora several years ago and I really loved it. Some of you might remember Eudora from back then. Some of you may have also been using the paid Eudora the past few years. I think Eudora is a great mail client.
Qualcomm decided to eliminate the paid Eudora and allow it to become open source. It is now an extension built on top of Thunderbird.
Eudora 8 allows you to add any menu item to the toolbar. It also supports Thunderbird add-ons.
Penelope extentions will work with either Eudora or Thunderbird and they provide new icons and sound files.
Eudora is a branded version of Thunderbird that has some extra features from the Eudora developers. Penelope is an extention that can be used with either Thunderbird or Eudora.
You need to remember that Eudora 8 is a beta release so everything might not be perfect.
Here is a link that will tell you all about Eudora and allow you to download it
Penelope Releases - MozillaWiki