Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
blat - Blat is a small, efficent SMTP command line mailer for Windows.
sSMTP - sSMTP is a simple MTA to deliver mail from a computer to a mail server.
mailsend-go - mailsend-go is a command line tool to send mail via SMTP protocol, written with golang.
OpenSMTPD - OpenSMTPD is a FREE implementation of the server-side SMTP protocol as defined by RFC 5321, with...
CMail - CMail is a free Windows command line mailer with advanced message formatting options.