Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
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.
Smartmockups - Create stunning product mockups, easily and online.
MJML - The open source framework for responsive emails
MockMagic - A free, easy-to-use device mockup generator