If you're attempting to send marketing emails, then yes, absolutely, that's exactly how it should work. If someone, say, signs up for an account on your websit

If you're attempting to send marketing emails, then yes, absolutely, that's exactly how it should work. If someone, say, signs up for an account on your website and opts-in to marketing emails, then sure, you can send them marketing emails. If you have no relationship with someone, or they haven't opted in, no, you should never send them even a single marketing email.