curl -X POST https://api.qwikmailer.in/v1/send \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "user@example.com",
    "subject": "Hello!",
    "html": "<h1>Hi there!</h1><p>Welcome aboard.</p>"
  }'