curl -X POST https://smtp-relay.hitechcloud.vn/api/v1/email/send \
  -H "Authorization: Bearer htc_live_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "contact@hitechcloud.vn",
    "to": "thanhan635916@gmail.com",
    "subject": "HiTechMail API Delivery Test",
    "html": "<h2>Hello World</h2>",
    "priority": "P0"
  }'

const res = await fetch('https://smtp-relay.hitechcloud.vn/api/v1/email/send', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer htc_live_your_api_key',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    from: 'contact@hitechcloud.vn',
    to: 'thanhan635916@gmail.com',
    subject: 'HiTechMail API Delivery Test',
    html: '<p>Message content</p>'
  })
});
const data = await res.json();
console.log('Message ID:', data.messageId);