5.2. Installing Thunderbird / SeaMonkey

Thunderbird is a standalone email client, while SeaMonkey is a suite that incorporates a mailclient, a browser, an HTML composer, and an IRC client.
Both stem from the Mozilla project. The mailclient interface and functionalities are similar, and you can choose the one you prefer. You can download Thunderbird from http://www.mozillamessaging.com/thunderbird or SeaMonkey from http://www.seamonkey-project.org.

Many Linux distributions ship with their own customized version of Thunderbird.
If you use your distribution's version of Thunderbird, you must use your distribution's version of Enigmail. If you get Thunderbird from the official site and install it yourself, though, you can use the official Enigmail releases provided by the Enigmail Project.
Thunderbird and SeaMonkey have their excellent documentation and user group support, hence we'll skip the steps to install and configure them.
You should have your mailclient and your email account fully configured before proceeding to the installation of Enigmail.