You don’t need anything in your inbox that you didn’t ask for. You may have to sign up on a website, but that’s about the only safe way to do so, and even then, people get exhausted to getting things and may mark you as spam after a bit any way. Instead, let them opt in, and then have it replenish so they can decide if they need to replenish or not. To keep your clients cheerful, ensure you assemble your list the proper way.