Opt-in means someone actively chose to receive your marketing communications. This typically happens through a form submission, checkbox, or signup flow where the person provides their email address with the understanding that they will receive marketing content.
There are two levels of opt-in. Single opt-in adds someone to your list immediately after they submit their email. Double opt-in requires a confirmation step where the person clicks a link in a verification email before being added. Double opt-in produces a cleaner list but reduces signup conversion rates.
Under GDPR, opt-in consent must be freely given, specific, informed, and unambiguous. Pre-checked checkboxes do not qualify. Burying consent language in terms of service does not qualify. The person must take a clear affirmative action to agree to receive marketing emails.
For US-based companies operating under CAN-SPAM, opt-in is not legally required, but it is strongly recommended for practical reasons. Lists built on opt-in have higher engagement rates, lower complaint rates, better deliverability, and lower unsubscribe rates. The deliverability benefits alone justify the practice.
MOps teams implement opt-in through form configuration (explicit checkboxes for marketing consent), MAP settings (honoring consent status in email sends), CRM field management (tracking consent status and timestamp), and preference center design (letting subscribers manage what they receive). Build these systems once and maintain them as your compliance posture evolves.