title: Google Apps Script - check if an email has sent properly
body: <p>I'm working on a Google Apps Script project that sends an email when a button is clicked on a HTML sidepanel I've built. Currently the script works as planned and fires off an email when told, but I'm wondering if there's any way that it could check that the email sent correctly so I can notify the user that it's ok to close the tab? </p>
  
  <p>Thanks in advance</p>