Mozilla is one of the best IT Organization. They Innovate Mozilla Thunderbird as mail client, its an free software and easy to use. Its really a trusted software now-days cause most of the mail client software are not free and not secured as Mozilla.
Free Download Link-
This software also available for Windows, linux and Mac also. Please Comment If you like my post. Thunderbird a very open source and trusted mail client and its also free, when you get a free mail client why you use paid or licensed version.