Roundcube - Web-based IMAP email client
Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.
sSMTP - sSMTP is a simple MTA to deliver mail from a computer to a mail server.
Rainloop - RainLoop is a web based email client.
Sendmail - Sendmail is a general purpose internetwork email routing facility that supports many kinds of...