I like Readwise.io
It basically syncs your bookmarks and highlights from books you read and turns them into flashcards. I tend to highlight a lot but never actually looked at the highlighted text, Readwise solved that for me.
Mailjet looks really good for my usecase. Thank you for the recommendation @denemio !
I never had any problems with Mailchimp, it’s just a very expensive solution sometimes. Recommended if you’ve got money burning a hole in your pocket.