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  • The API base URL is https://app.letterbucket.com/api/v1/.
  • The newsletter is resolved from the API key — you do not pass a newsletter ID.
  • name is stored internally as first_name + last_name, split on the first space.
  • status is optional in POST /api/v1/subscribers, POST /api/v1/subscribers/bulk and PUT /api/v1/subscribers/{id}.
  • Allowed input status values are active and pending.
  • Response status values are strings: pending, active and unsubscribed.
  • GET /api/v1/subscribers supports ?status=active, ?status=pending and ?status=unsubscribed.
  • Invalid status filter values return 400 with a descriptive message.
  • Subscriber list and get endpoints are cached in Redis with a 1 hour TTL.
  • Duplicate email within the same newsletter returns 422 with code email_already_subscribed.
  • The API key scope is limited to the newsletter it was created for.