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 < contacts.length; i++) {
    // get current email address
    email = contacts[i].getPrimaryEmail();

    // check if email is not null
    if (!(email == null)) {
      // check message count
      count = GmailApp.search('from:' + email).length;

      // if count is zero or null then add that user to Group called Blacklist
      if (count == 0 || count == null) {
        // add this user to the "ToBeDeleted" contact group
        group.addContact(contacts[i]);
      }
    }
  }
}