What are some alternatives?
When comparing Responsive Email and Responsive View, you can also consider the following products
Adapti - Create a unique web experience for each of your users
Placid - Generate og:images and twitter:images automatically
SlideRule UX Design Path - Curriculum of Online Courses To Learn UX Design
Froala Design Blocks - 170+ free responsive design blocks based on Bootstrap 4
Am I Responsive - see your website in multiple screen resolutions
Responsive Image Breakpoint Generator - Turn one image into the ideal set of per-device images