Mozilla Thunderbird

Mozilla Thunderbird is a free,[6] open source, cross-platform email, news and chat client developed by the Mozilla Foundation.

The project strategy was modeled after Mozilla Firefox, a project aimed at creating a web browser. On December 7, 2004, version 1.0 was released, and received over 500,000 downloads in its first three days of release, and 1,000,000 in 10 days.[7][8]

On July 6, 2012, Mozilla announced the company was dropping the priority of Thunderbird development because the continuous effort to extend Thunderbird's feature set was mostly fruitless. The new development model is based on Mozilla offering only "Extended Support Releases", which deliver security and maintenance updates, while allowing community to take over the development of new features