Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
Stream UI Kit - A beautiful open source Bootstrap 4 UI kit
MJML - The open source framework for responsive emails
Render UIKit - React-inspired Swift library for writing UIKit UIs
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.
Fitnesly - Fitness UI kit based on Eva Design System