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Use the Newsletter Public API to create, list, update and unsubscribe newsletter subscribers from external integrations. This reference covers the endpoints, authentication, response formats, caching behavior and request limits.

Base URL

app.letterbucket.com/api/v1/

Authentication

Bearer API key

Rate limited

Per minute, hour and day

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What you can do

Create subscribers

Add one subscriber, or up to 100 at once with bulk create.

List & retrieve

Paginated listing with optional status filters.

Update subscribers

Change email, name or status.

Unsubscribe

Set a subscriber to unsubscribed.

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Conventions

  • All requests and responses use application/json.
  • The newsletter context is resolved from the API key — you do not pass a newsletter ID.
  • Subscriber IDs are UUIDs (for example 019756c2-...).