title: document.referrer value when clicked from email box
body: <p><strong>document.referrer</strong>  Returns the URI of the page that linked to this page.
  The value is an empty string if the user navigated to the page directly (not through a link, but, for example, via a bookmark),</p>
  
  <p>as <a href="https://developer.mozilla.org/en-US/docs/Web/API/Document/referrer" rel="nofollow noreferrer">https://developer.mozilla.org/en-US/docs/Web/API/Document/referrer</a>  states.</p>
  
  <p><strong>My question is:</strong></p>
  
  <p>When we click on the link within an email account from the browser, we land on the page where document.referrer is empty.</p>
  
  <p>At least it's valid for several email providers I've tested when clicked on ads/URLs within subscribed newsletter emails I receive.</p>
  
  <p>Will it be true for any email provider or not true? </p>
  
  <p>I need to filter (no the exact criteria though) visitors when link was clicked from customer's email.</p>
  
  <p>With another words, if document.referrer is NOT empty, does this mean the customer definitely came to my web site NOT from email link (not from Yahoo, not from Google etc)?</p>