Passive opt-in refers to a method of obtaining consent from individuals to receive marketing communications, where the individual’s silence or inaction is considered as a form of agreement. This means that unless the individual actively opts out, they are automatically included in the marketing list. This approach is often used in email marketing and is seen as a less intrusive way of obtaining consent compared to active opt-in, where individuals have to explicitly give their consent. However, it is important for businesses to ensure that the individual is aware of and understands the implications of passive opt-in, and that they have the option to easily opt-out at any time.