One API for newsletters and every other email.

POST /api/v1/{slug}/send
API-KEY: ••••••  API-SECRET: ••••••

{
  "from": "[email protected]",
  "to": "[email protected]",
  "subject": "Your order #10023",
  "html": "<p>Thank you for your order.</p>"
}

POST /api/v1/{slug}/posts
API-KEY: ••••••  API-SECRET: ••••••

{
  "subject": "Our November update",
  "html": "<p>Hello, here is what is new …</p>",
  "send_at": "2026-11-14T07:30:00+01:00"
}

POST /api/v1/{slug}/add-subscriber
API-KEY: ••••••  API-SECRET: ••••••

{
  "email": "[email protected]",
  "segments": ["Buyer", "Hamburg"]
}