The mail inbox is typically a one-way road: We send mails and the user reads or ignores the mail, and maybe clicks on a link.
I think there should (and can) be more interaction via email, from the reader/customer to the writer/company:
I would like to embed forms inside emails to ask subscribers for feedback - e.g. right after subscription ("what content are you most interested in"), after a purchase ("please write a short review"), etc.
Some notes and samples:
  1. Technically it's possible, sends review-forms via email a few days after the purchase. A screenshot of that email is below.
  2. Here's an article on that topic:
  3. For me (and other devs) a valid solution could be, to have an API that allows us to code the HTML form, as suggested here: