Eudora is now free, cross platform, and based on the Mozilla & Thunderbird code:
Penelope is an open source extension to the Mozilla Thunderbird mail application.
Qualcomm's intention with the Penelope project is to join the Eudora® user experience with the Mozilla platform. We intend to produce a version of Eudora that is open source and based on Mozilla and Thunderbird. It's not our intention to compete with Thunderbird; rather, we want to complement it.
Qualcomm is committed to both preserving the Eudora user experience and to maintaining maximum compatibility, for both developers and users, with Thunderbird. It is our goal to build a single development community around Thunderbird and Eudora, so that both mailers advance faster than they previously have.
