QUALCOMM Press Center – QUALCOMM Launches Project in Collaboration with Mozilla Foundation to Develop Open Source Version of Eudora Email Program –link
Eudora was my email client of choice back in the day, when webapps were still so much crappier. I suppose they realized so many people had switched to using either GMail or Thunderbird, that they had to do something to make their product relevant.
My favorite thing about Eudora was that their client would have a stats page; it literally tracks the amount of time you spend reading and writing email, the average amount of mail you get daily, etc. Productivity geeks would love it if something similar came to Thunderbird so they can easily measure how much time they spend in their inboxes.