function DeleteBySender() {

  var sender="asdf@ghjkl.com"
  var threads = GmailApp.search("from:" + sender);
  var me = Session.getActiveUser().getEmail();
  Logger.log("Found " + threads.length + " threads with sender " + sender);

  for (var i = threads.length -1; i >=350; i--) {
     var thisid=threads[i].getId();
     /*Logger.log("Removing thread " +i + ' of ' + threads.length + " from " + sender + " with ID = " + thisid);*/

    try {
        Gmail.Users.Threads.remove(me, thisid);
    }
    catch(err) {
     Logger.log("Error " + err.message + " when removing thread with ID " +thisid);
    };
  }

  Logger.log("Deleted approx emails: " + (500-i-1));


}