Product Disrupt might be a bit more popular than MJML App. We know about 1 link to it since March 2021 and only 1 link to MJML App. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Check out the MJML framework: https://mjmlio.github.io/mjml-app/. Source: almost 3 years ago
Product Disrupt - Curated List of Resources to Learn Product Design. Source: about 3 years ago
HTMLEmail.io - Responsive HTML email templates for startups & developers
Design Principles - An open source repository of design principles and methods
MJML - The open source framework for responsive emails
Colorbox.io - Create accessible color systems 🎨
Foundation for Emails 2 - Create responsive HTML emails that work on any device
Laws of UX - Key maxims that designers must consider when building UX