curl -X POST https://api2.ecomailapp.cz/domains \
  -H "key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "newdomain.cz"
  }'

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'https://api2.ecomailapp.cz/domains');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'key: YOUR_API_KEY',
    'Content-Type: application/json',
]);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode([
    'name' => 'newdomain.cz',
]));
$response = curl_exec($ch);
curl_close($ch);

{
  "name": "newdomain.cz",
  "valid": 0
}