tmux - tmux is a terminal multiplexer: it enables a number of terminals (or windows), each running a...
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
GNU Screen - Screen is a full-screen window manager that multiplexes a physical terminal between several...
Geary - Geary is an email application built for GNOME 3.
Zellij - A terminal workspace with batteries included
The Bat - The Bat! is a secure desktop email client for Windows, designed to protect your correspondence against third-parties and to save your time.