blat - Blat is a small, efficent SMTP command line mailer for Windows.
CMail - CMail is a free Windows command line mailer with advanced message formatting options.
Mailer - Free utility to send emails from the command line. No Installation. All contained in one file.
sSMTP - sSMTP is a simple MTA to deliver mail from a computer to a mail server.
CheFSender - CheFSendeR is a simple command line tool to send emails.
msmtp - msmtp is an SMTP client.