Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
Stripo - Stripo is an all-in-one email design platform. We enable our clients to build emails of any complexity, including interactive AMP emails, really fast and easy.
MJML - The open source framework for responsive emails
BeeFree.io - Bee is MailUp's drag-&-drop editor for responsive design emails.
Startup Emails - Responsive HTML email templates for startups
Elite Email - Drag & drop email builder for awesome newsletters