Quick Start.

Overview

SMTPfast is a developer-first email API built for speed and simplicity. Send transactional emails, manage sending domains, and track delivery events through a clean REST API.

The API is compatible with Resend, so you can switch with minimal code changes.

Base URL

https://smtpfa.st/api/v1

All endpoints described in these docs are relative to this base URL.

Authentication

Every request requires a Bearer token in the Authorization header. Create an API key from your dashboard or via the API.

Authorization: Bearer sf_live_your_api_key

Send Your First Email

Make a POST request to /v1/emails with the recipient, subject, and body.

curl -X POST https://smtpfa.st/api/v1/emails \
  -H "Authorization: Bearer sf_live_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "[email protected]",
    "to": ["[email protected]"],
    "subject": "Welcome!",
    "html": "<h1>Hello from SMTPfast!</h1>"
  }'

Response Format

Responses are JSON, apart from exports such as /v1/contacts/export which returns CSV. A successful request returns 200, or 201 when it created something. An error carries an error field with a message that describes the issue; the HTTP status code says what kind of error it is.

{
  "id": "email_abc123"
}

{
  "error": "Invalid API key"
}