HTMLEmail.io - Responsive HTML email templates for startups & developers
Really Good Emails - A large collection of good product email design.
UI Jar - Hand-picked design inspiration for your real life projects
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
UI Movement - The best UI design inspiration, daily
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.