Under your email subscribers, Medium gives you the option to "import subscribers." So, basically they would have to add you to a CSV file with other subscribers they may or may not have consent from. Then, you can upload that file and add those people to your list. People get my email from my link tree, which is in my bio, I'm assuming. I have it there for when others want to connect outside of Medium, or have a question about freelance work. Not really wanting to take it out of there because it serves a purpose for me!