What is the best way to forward visitors to my homepage to an external site but leave the backlinks accessible?
It sounds like one thing you could do is edit the themes template.php file and do something like:

/**
 * Implements template_preprocess_html().
 */
function mytheme_preprocess_html(&amp;$variables) {
  if (drupal_is_front_page()) {
    $url = 'http://newdomain.com';
    drupal_goto($url, ['external' =&gt; TRUE], 301);
    // perhaps alternatively you could use header();
  }
}


Outside of doing this at the web server level, it might be the smallest change to do it.