Both GDPR and the CAN-SPAM Act demand that any B2C email has to allow for an easy procedure to unsubscribe from further correspondence. That typically means a linked “unsubscribe” at the bottom of the email.
It should be visible and accessible. According to the CAN-SPAM Act, if an opt-out request is B2C Email Address List submitted, businesses have to act upon it within a certain given deadline usually about 10 days, and there should not be more than a few clicks associated with this procedure.
What GDPR adds is that subscribers must have an easy way to manage their subscription preferences and even withdraw consent, which means businesses must ensure there is a smooth process for honoring those said preferences.