Stamplia - High converting and beautifully designed email templates
Really Good Emails - A large collection of good product email design.
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.
Pistachio Email Templates - Delicious newsletter templates built for automation
Email Design System for Sketch - Sketch file with 10 email templates for designers
Passport by Mailjet - Create beautiful, responsive e-mails