Email Kick - Email designer and analytics for your transactional emails.
Blush - Illustrations for everyone
Really Good Emails - A large collection of good product email design.
Interfacer - Collection of more than 200+ free design resources
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.
Neede - An online design resource library