useremailvalidation.js

function onPreSave(request, response, modules) {
  if (request.body.email === undefined) {
    return response.error("Validation Failed, registering users requires an email");
  }
  if (request.body.email.toLowerCase().indexOf("@kinvey.com") == -1){
    return response.error("Validation Failed, Registration is only available for employees!");  
  }
  response.continue();
}