Marble Responsive Email Designer - Marble helps you design beautiful and mobile-friendly emails and newsletters.
Topol.io - Create professional Email templates easily - Drag & Drop Email Builder.
Flexmail Solution - Professional email marketing with powerful and easy-to-use features
BeeFree.io - Bee is MailUp's drag-&-drop editor for responsive design emails.
Mizmoz - Easy-to-use, state of the art, email service provider dedicated to support growing businesses.
MJML - The open source framework for responsive emails