title: Google Spreadsheets: Can't Fetch User Email via Session.getActiveUser().getEmail()
body: <p>So I have a spreadsheet that is supposed to automatically fetch every users' emails and assign custom usernames for their emails. I use this data to display a per-row "last edited by ---" on a sheet. This also allows me to list all the users viewing the spreadsheet and log when they last opened it.</p>
  
  <p>However, the Session.getActiveUser().getEmail() returns a blank string for anyone else other than me.</p>
  
  <p>I've seen that you could make it so that the scripts run under the user's account. But that is only for deployed web apps. I need to integrate it to spreadsheets. Any ideas on how I should do that?</p>