function email(domain) {
  var spantags = document.getElementsByTagName('span');
  var stlength = spantags.length;
  for (i = stlength - 1; i >= 0; i--) {
    if (spantags[i].className == 'emailadres') {
      var address = spantags[i].innerHTML + '@' + domain;
      var mailto = document.createElement('a');
      mailto.href = 'mailto:' + address;
      mailto.appendChild(document.createTextNode(address));
      spantags[i].parentNode.replaceChild(mailto, spantags[i]);
    }
  }
}

window.onload = function() {
  email('hk-solutions.nl');
}