⚙️ API reference

API reference

Everything a developer needs to integrate GO MAILBOX in an afternoon.

Overview

A small, predictable API

Authenticate with a header, POST JSON, get JSON back. No SDK required — anything that can make an HTTP request can use it.

  • Header-based API key authentication
  • Add subscribers with custom field values
  • Send transactional email from a verified domain
  • List your lists and subscriber counts
⚙️
What you get

Key capabilities

🔑

Authentication

Send X-Api-Key with every request. Generate keys in your dashboard.

👥

subscribers.create

Add a contact to a list, including custom fields.

✉️

transactional.send

Send a one-off email from your verified domain.

📋

lists.list

Retrieve your lists with live subscriber counts.

Great for

Who uses this

Developers

SaaS integrations

Ecommerce platforms

Internal tools

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