title: Error from Mailgun API when try to create a domain
body: <p>When I try to create a domain from the <strong>Mailgun API</strong> (i.e. <code>POST /domains</code>) I receive an error :</p>
  
  <blockquote>
    <p><strong>"One of your domains is permanently disabled. You are not allowed to create new domains.".</strong></p>
  </blockquote>
  
  <p>I couldn't find this error documented anywhere and I'm only guessing what it means. Any help would be appreciated.</p>