Google Script thread muter

Code.gs

// Enforce thread muting
// When you mute a thread in Gmail, it adds a "Muted" label
// Unfortunately, it doesn't really completely mute the thread - e.g. emails added to the thread will still be marked as unread and show up against folder counts
//
// This script will ensure that all emails appearing on muted threads, will be marked read, and archived.
//
// By default it will only look for emails that are less than 3 days old, to limit the size of the query results. You can adjust that if you want to
var age_max="3d"

function enforceMutes() {
  var threads = GmailApp.search("label:Muted is:unread " + " newer_than:" + age_max);
  for (var thread_key in threads) {
    var thread = threads[thread_key];
    Logger.log("  Archiving: " + thread.getFirstMessageSubject());

    thread.markRead();
    thread.moveToArchive();
  }
}