Weightless.so

Weightless started as an email address capture tool for landing page + waitlist scenario, but it soon evolved into a full newsletter platform. As the name suggests, it doesn't try to do much: it only helps you collect email addresses, and send messages to them, the simplest way possible. You'll find no HTML email templates or WYSIWYG editors. It doesn't even have any user interface or dashboard to log in to: you use it entirely from your email client like Gmail, Outlook, Apple Mail, or any other.