deleteOldMessages.js

function main() {
  deleteOldMessages('notifications-jenkins');
  deleteOldMessages('notifications-sentry');
}


function deleteOldMessages(label_to_delete) {
  var search = 'label:' + label_to_delete + ' -{label:Trash} older_than:6m';
  var threads = GmailApp.search(search, 0, 120);
  
  console.log("Search: `" + search + "` (" + threads.length + " threads)");
  
  for (var i in threads) {
    var thread = threads[i];
    var subject = thread.getFirstMessageSubject();
    
    thread.moveToTrash();
    
    console.log("Moving to the trash: " + subject);
  }
  
}

Used in https://script.google.com