CMail - CMail is a free Windows command line mailer with advanced message formatting options.
mailsend-go - mailsend-go is a command line tool to send mail via SMTP protocol, written with golang.
sendEmail - sendEmail is a lightweight, command line SMTP email client.
CheFSender - CheFSendeR is a simple command line tool to send emails.
Mailercloud - Mailercloud is a cloud-based email marketing tool, enriched with great features, which help users to build strong relationships with their audience. It is ideal for those who wish to improve engagement rate and conversions.
sSMTP - sSMTP is a simple MTA to deliver mail from a computer to a mail server.