Sylpheed is a free and open source email client application for Windows, Linux and MacOS. It comes with 3-paned display and you can also customize the behavior of mail display, easy configuration, easily backup your mail data, build-in filtering and search, junk mail control, extend its feature by plugins, multi-thread support and many more.
How to Install Sylpheed on Ubuntu
To install Sylpheed on Ubuntu, run below command in your terminal (ctrl+alt+t) application.
sudo apt install sylpheed -y
It will install the latest version of Sylpheed on your system. Now open it using the below command or via Show Apps button from Ubuntu dock.