Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
sSMTP - sSMTP is a simple MTA to deliver mail from a computer to a mail server.
Geary - Geary is an email application built for GNOME 3.
Sendmail - Sendmail is a general purpose internetwork email routing facility that supports many kinds of...
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.