Plugin that allows sending of different content to members

Hello, I have 20 day lessons (say, Lesson 1 to 20) and want to send each lesson content for my wordpress site’s members. When a member clicks on a button to express interest in receiving the lesson emails, I’d like him/her to start receiving content from that day. This means that different members will be receiving different lessons, depending on when he/she initiates. Is there a plug-in that allows this? Thank you for your suggestions.