Existing customers: When a user has made a purchase from us or has taken any of our sample quizzes, MailChimp automatically sends them an email on our behalf. If the user hasn't clicked on "Unsubscribe," they are automatically subscribed to our newsletter and should get them once-monthly. The newsletter is setup in such a way where it only gets sent to those who have given their Marketing Consent (and not those who have Unsubscribed).
New customers (i.e. would-be customers): One option we can do for them is that the Marketing Manager can manually enroll the customer (screenshot below). Just send the customer's first and last name, as well as their email address (they can Unsubscribe at any ime as all our emails have an "Unsubscribe" link at the bottom.