MJML - The open source framework for responsive emails
Really Good Emails - A large collection of good product email design.
Email Design System for Sketch - Sketch file with 10 email templates for designers
Email Love - Email design inspiration, templates and discovery
Getform - Smart form endpoints. The modern way to build the form backend.
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.