On other such services, using a URL shortener can allow linking to web pages which would otherwise violate this constraint. To view stats for your custom campaigns go to Google Analytics Reporting » Traffic » Sources » Campaigns and you will see something like this. Clicks per unique opens Percentage of recipients who opened your campaign and then clicked a link. And though it is unlikely that Bit.ly will be shut down, they are still a middleman. See if you are using Classic Analytics (ga.js) or Universal Analytics (analytics.js).