blat - Blat is a small, efficent SMTP command line mailer for Windows.
Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
sendEmail - sendEmail is a lightweight, command line SMTP email client.
mailcow - An open source mailserver suite.
CMail - CMail is a free Windows command line mailer with advanced message formatting options.
Mail-in-a-box - Mail-in-a-Box provides webmail and an IMAP/SMTP server for use with mobile devices and desktop mail software and also includes contacts and calendar synchronization.