May I email a newsletter to past customers?

Existing-customer-relationship exception (Tw 11.7(4)): you may email commercially to existing customers for similar services, provided opt-out in every expression + easy unsubscribe. Conditions: (1) Customer previously had paid agreement — not just "subscribed to newsletter". (2) Similar service — strictly interpreted. E.g. bookshop can email about new books. NOT about "we now have insurance". (3) Opt-out in every email — unsubscribe link clearly at bottom. (4) Customer was informed at purchase that marketing could follow. How long does "existing relationship" apply? No statutory deadline. AP guideline: 3 years after last purchase the "existing customer" status is usually exhausted. After that new opt-in required. What is ALWAYS required: consent for new audiences (people who never bought), newsletter signup via form. Double opt-in (send confirmation email with activation link) = best practice + proof of consent. Profiling existing customers for marketing: separate basis (legitimate interest with balancing test or consent). Not automatically under existing-customer exception. Fine risk: AP enforcement 2023-2025 against energy companies + telcos defining "existing customers" up to 10+ years old.