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API reference

Lettermint exposes two public API surfaces. They use different token types and are meant for different jobs.

Sending API

Send transactional or broadcast email with a Project API token in the x-lettermint-token header.

Team API

Manage team resources with a Team API token in the Authorization: Bearer header.

Authentication

APITokenHeaderTypical use
Sending APIProject API token, lm_...x-lettermint-tokenSend email from one project
Team APITeam API token, lm_team_...Authorization: BearerManage domains, projects, routes, webhooks, messages, suppressions, and usage

Never expose Project API tokens or Team API tokens in client-side code. Store them in environment variables or a secrets manager.

Try the API

Next steps

  • Quickstart - Send your first email
  • Project API tokens - Create sending credentials
  • Team API tokens - Create management credentials
  • Production checklist - Prepare a production integration
Last modified on August 7, 2026
SDKs & Integrations
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