Rate Limiting

Mail.cx applies rate limits to ensure fair usage and service stability.

Limits

Rate Limit	Description
8 req/s per IP	All endpoints (/api/ and /pro/api/)

Rate Limit Response

When you exceed the limit, the API returns 429 Too Many Requests:

{
  "error": "rate_limited",
  "message": "Too many requests, please slow down"
}

Best Practices

• Use WebSocket for real-time updates instead of polling GET /api/messages repeatedly
• Cache domain lists — available domains rarely change
• Use exponential backoff when retrying after a 429
• Batch operations where possible — don't create/delete accounts in tight loops

Example: Retry with Backoff

async function fetchWithRetry(url, options, maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    const res = await fetch(url, options);
    if (res.status !== 429) return res;

    const delay = Math.pow(2, i) * 1000; // 1s, 2s, 4s
    await new Promise(r => setTimeout(r, delay));
  }
  throw new Error('Rate limit exceeded after retries');
}