CMail - CMail is a free Windows command line mailer with advanced message formatting options.
Maileroo - Maileroo is a powerful email delivery platform, featuring a user-friendly SMTP service and Email API. It specializes in supporting transactional emails with advanced features like delivery tracking, as well as detailed open and click monitoring.
blat - Blat is a small, efficent SMTP command line mailer for Windows.
Postmark Express - What happens to your emails after you hit the "send" button?
sendEmail - sendEmail is a lightweight, command line SMTP email client.
Warmup Inbox - Warmup Inbox is a tool that automates the process of warming up your email inboxes, raising your sender reputation and inbox health automatically.