Consent

A customer who sends STOP is suppressed across every category, including transactional. Sends return 403 consent_required until they opt back in.

Two things lift it, and they lift different amounts. If the customer messages you again, that alone clears the suppression; they wrote to you, so you may answer. If they send SUBSCRIBE, that clears the suppression and re-grants marketing, but only marketing. No keyword can re-grant account_notification; that one needs its own disclosure.

Lifting it doesn’t rescue sends already in flight. A message you queued before the customer opted out stays suppressed and finishes as message.failed with reason consent_revoked.