Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
PowerMTA - PowerMTA is an industrial-strength software for high-volume email delivery.
sSMTP - sSMTP is a simple MTA to deliver mail from a computer to a mail server.
EmailSuccess - EmailSuccess is an advanced MTA built to handle the most critical reliability, performance, security, and deliverability requirements.
OpenSMTPD - OpenSMTPD is a FREE implementation of the server-side SMTP protocol as defined by RFC 5321, with...
Exim - Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems connected to the Internet.