Google Script for deleting automated emails

purge.gs

// The name of the Gmail Label that is to be autopurged?
var LABELS = ["alerts-disk-space", "alerts-sensu", "backups", "cron", "janitor-monkey", "nagios", "push", "security-alerts", "svn-git-updates"];
 
// Purge messages automatically after how many days?
var PURGE_AFTER = "31";

// This is the largest batch size moveThreadsToTrash supports
var BATCH_SIZE = 100
var DELAY_BETWEEN_MS = 1000

function purgeLabel(label) {
  var age = new Date();
  age.setDate(age.getDate() - PURGE_AFTER);    
  var purge  = Utilities.formatDate(age, Session.getScriptTimeZone(), "yyyy-MM-dd");
  // This will create a simple Gmail search 
  // query like label:Newsletters before:10/12/2012
  var search = "label:" + label + " before:" + purge;
  while (true) {
    // Grab a batch of threads
    var threads = GmailApp.search(search, 0, BATCH_SIZE);
    // Break if there's nothing to do
    if (threads.length == 0) {
      break;
    }
    GmailApp.moveThreadsToTrash(threads);
    // Sleep in-between deletes or we may get killed for calling the API too quickly 
    Utilities.sleep(DELAY_BETWEEN_MS)
  }
}

function main() {
  for (var i=0; i<LABELS.length; i++) {
    Logger.log("Deleting from %s", LABELS[i]);
    purgeLabel(LABELS[i])
  }
}