Despite what the media may have made you think, no. There are six lawful bases under GDPR, of which two are relevant for email marketing - consent and legitimate interests. You can send emails to customers or prospective customers provided you either have their consent to do so (they have opted in) or they have provided you with their information and it would be reasonable and in your legitimate business interests to communicate with them. As an example, if you obtained someone's details when they made an enquiry into buying one of your products, you would have a legitimate interest in sending them further emails to win the sale, and it would be reasonable for you to do so, unless they were to then ask you not to (by opting out or unsubscribing). However, if you collected their details when they made an enquiry asking for advice about repairing one of your products, you couldn't reasonably believe they have any intention to buy from you, and therefore it would be illegal to send them any communications unless they consented. You must keep a record of what lawful basis you are using for every customer, which is why some businesses prefer to simplify things by only relying on consent.