Audience

Everything about who receives an email lives here. Five objects, and they do not overlap.
ObjectScopeSet byAnswers
Listorganizationyouwho is subscribed to what
Contactone listyou and the recipientmay we write to this person
Tagorganizationyouwho this person is
Segmentone listyouwhich part of the list to reach
Topicorganizationthe recipientwhich theme they refuse
Two rules explain most of the behaviour that follows. A contact belongs to exactly one list. The same address in two lists is two contacts, with two histories and two unsubscribe links. Subscription — and unsubscription — is per list, not per person. Only the recipient decides to stop. You own tags and segments; the recipient owns their state, their consent dates and their topic refusals. Nothing you run — an import, a bulk API call, a deletion — is allowed to overwrite that by accident, which is why several operations here refuse instead of doing something plausible. Getting contacts in: by hand, through an import, through a sign-up form with double opt-in, or through the Audience API. Each of them records where the contact came from, and none of them sends anything on its own.