$(document).ready(function () {
  var domain_parts = location.hostname.split('.');
  $('a[href^="http://"],a[href^="https://"]').filter(function() {
    var parts = this.hostname.split('.');
    return (domain_parts[domain_parts.length - 2] + "." + domain_parts[domain_parts.length - 1]) !== (parts[parts.length - 2] + "." + parts[parts.length - 1]);
  }).attr('target', '_blank');
});