Bookmarklet to remove the proxy GMail uses to display images in img tags. It enables me to test content in emails from sites not exposed to wide Internet.

NoGMailProxy.bookmarklet.js

/*
 * GMail's image proxy gets in the way when testing emails that are coming from testing websites that we do not expose
 * to the general internet. This bookmarklet code will remove the proxy in the URI of all HTML img tags on the current
 * page and update the src attribute with the non-proxy version of the content URI. All src tags that do not use the
 * Google User Content proxy service will be left alone. To use this, copy the code into the URL field of a new bookmark
 * in your browser. Then, when looking at an email that has images provided by the proxy, click the bookmark and the
 * images should appear.
 */

javascript:(function() {
  var images = document.getElementsByTagName('img');
  for (var i = 0; i < images.length; i++) {
    var hashIndex = images[i].src.indexOf('#');
    images[i].src = images[i].src.substring(hashIndex + 1);
  }
}());