Bravo!
Genius!
Very easy to use.
I had been searching for a long time for a way to get the Featured Image from WP blog posts to appear in MaiChimps RSS to Email option.
I searched MailChimp and Google. Finally I found this plug in. Now MailChimp just instantly has the image.
I did not need to switch to the full content option in MailChimp, although I did briefly.The excerpt option displays the image as well which created a duplicate. So I removed the full content MailChimp shortcode.
Plus there is a support thread about how to make the image responsive.
https://wordpress.org/support/topic/responsive-featured-images-in-rss?replies=11#post-7050154
Very helpful.
Thank you and next time your in AZ I owe ya a beer.