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Requests are sent to a single centralized API path, and the newsletter context is resolved from the API key itself — you never pass a newsletter ID.

Base URL

https://app.letterbucket.com/api/v1/

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Request flow

Client
  ↓
https://app.letterbucket.com/api/v1/
  ↓
Authorization: Bearer sk_xxxxx
  ↓
API validates the key, capabilities, throttling and payload
  ↓
Newsletter is resolved from the API key
  ↓
Subscriber operation
  ↓
Standard JSON response
Do not publish permanent production API keys. For demo usage, prefer short-lived sandbox keys with low limits and periodic data cleanup.