- See Wikipedia's article on Mozilla Thunderbird for more information.
On December 7, 2004, version 1.0 was released, which received over 500,000 downloads within its first three days of release , and over a million in ten days.
On June 2, 2005, Mozilla Thunderbird 1.1 Alpha 1 was released. Statistics of it's downloads aren't yet available. A stable release has not yet been released. 
Thunderbird is available for Windows, Mac OS X, and Linux in many different languages .