Configuration

Constructor

const send0 = new Send0(apiKey, config?);

Config options

Option	Type	Default	Description
`baseUrl`	`string`	Auto-detected	API base URL
`timeout`	`number`	`30000`	Request timeout in ms
`maxRetries`	`number`	`3`	Max retry attempts for 5xx errors

Examples

// Default configuration
const send0 = new Send0('sk_live_...');

// Custom configuration
const send0 = new Send0('sk_live_...', {
  timeout: 60_000,      // 60 second timeout
  maxRetries: 5,        // 5 retry attempts
});

// Custom base URL
const send0 = new Send0('sk_live_...', {
  baseUrl: 'https://custom-proxy.example.com/v1',
});

Base URL

The SDK defaults to https://api.send0.dev/v1. Override with baseUrl when running against a staging or self-hosted API:

const client = new Send0('sk_test_...', {
  baseUrl: 'https://staging.send0.dev/v1',
})

Retry behavior

Only retries on 5xx server errors
Never retries 4xx client errors
Uses exponential backoff
Configurable with maxRetries (set to 0 to disable)

// Disable retries
const send0 = new Send0('sk_live_...', {
  maxRetries: 0,
});

API key validation

All API keys must start with the sk_ prefix. The key prefix determines the environment and permissions:

Prefix	Meaning
`sk_live_`	Production key — real sends
`sk_test_`	Test key — sandbox only, no real delivery
`sk_restr_`	Restricted key — scoped permissions

Note: Using an sk_test_ key will never send real emails, regardless of the base URL or environment.