Mark Google Contacts with no Gmail Conversations

Your contacts list in Gmail is huge and you would like to trim it to only have email addresses with whom you have interacted at least once.

This Google Script, courtesy @crosenblub, will scan your entire address book and marks addresses with who you have never exchanged a single email conversation.

The contacts are put in a separate Google Contacts group making it easier for you to scan and clean the list.

function GetGmailContacts() {
  // get all contacts
  var contacts = ContactsApp.getContacts();
  // assign object for contact group    
  var group = ContactsApp.getContactGroup('ToBeDeleted');
  // loop through each contact
  for (var i=0; i