msmtp - msmtp is an SMTP client.
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.
Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
EmailSuccess - EmailSuccess is an advanced MTA built to handle the most critical reliability, performance, security, and deliverability requirements.
sendEmail - sendEmail is a lightweight, command line SMTP email client.