CMail - CMail is a free Windows command line mailer with advanced message formatting options.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
mailsend-go - mailsend-go is a command line tool to send mail via SMTP protocol, written with golang.
Brevo - Innovative online Email Marketing solution to manage your contacts, create & send your newsletters and track your results. More than 80 000 clients. Best prices and attractive features.
sendEmail - sendEmail is a lightweight, command line SMTP email client.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.