title: Generate valid email address from first and last name
body: <p>In our application we want to hide the real email address of the user (like craigslist), so we want to automatically create a masked email address based on their first and last name.<br>
  But the first and last name may contain characters that are invalid for an email address.</p>
  
  <p><strong>How do I safely generate a valid email address from first and last name?</strong></p>