Google Script to move e-mails to Trash

script.js

// You can install it at https://script.google.com/
// You can configure it to run every hour to move (eventually) all e-mails under "My Triggers". There are limits
// which prevents it to run for more than 6 minutes. So it is normal that it timeouts. But then there are also
// limits on how many times per day you can run it. So just make a trigger and let it run.

function myFunction() {
  while(true){
    Logger.log("Searching.");
    var threads = GmailApp.search('your search query', 0, 100);
    if (!threads.length) {
      Logger.log("Nothing found.");
      break;
    }
    Logger.log("Deleting threads.");
    GmailApp.moveThreadsToTrash(threads);
    Logger.log("Done.");
  }
}