O Mozilla Thunderbird is a free software application for tracking your e-mail or RSS feeds that interest you. The application is available on Microsoft Windows, Apple Macintosh and Linux operating systems.
Developed by the Mozilla Foundation, the first release was released on December 7, 2004. The first 1.000.000 downloads were made within 10 days of the first release. By 2007 the application had been downloaded 50.000.000 times.
The Thunderbird 78.0 is available for download from the project website and only supports MailExtensions and not the classic add-ons that supported older versions. So there is a possibility that some add-ons will no longer work in the new large version.
All the rest of you who are interested in the email client can download it on the platform you needed from official webpage.