MJML - The open source framework for responsive emails
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
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.
Missive - Team communication app now supporting FB, Twitter & SMS
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
Front - The platform for exceptional customer service at scale.