Node.js: Run the function on Event

function die(err) {
  console.log('Uh oh: ' + err);
  process.exit(1);
}

var box, cmds, next = 0, cb = function(err) {
  if (err)
    die(err);
  else if (next < cmds.length)
    cmds[next++].apply(this, Array.prototype.slice.call(arguments).slice(1));
};

cmds = [
  function() { imap.connect(cb); },
  function() { imap.openBox('INBOX', false, cb); },
  function(result) { box = result; imap.search([ 'UNSEEN', ['SINCE', 'April 5, 2011'] ], cb); },
  function(results) {
    var msgCache = {},
        fetch = imap.fetch(results, { request: { headers: ['from', 'to', 'subject', 'date'] } });
    console.log('Now fetching headers!');
    fetch.on('message', function(msg) {
      msg.on('end', function() {
        msgCache[msg.id] = { headers: msg.headers };
        console.log(msg.headers.date[0]);
        console.log(msg.headers.to[0]);
        console.log(msg.headers.from[0]);
        console.log(msg.headers.subject[0]);

        var from = /(.*)?<(.*?)>/.exec(msg.headers.from[0]);

        console.log(from[1]); // nome from
        console.log(from[2]); // from
      });
    });
    fetch.on('end', function() {
      console.log('Done fetching headers!');
      console.log('Now fetching bodies!');
      fetch = imap.fetch(results, { request: { headers: false, body: '1' } });
      fetch.on('message', function(msg) {
        msg.data = '';
        msg.on('data', function(chunk) {
          msg.data += chunk;
        });
        msg.on('end', function() {
          msgCache[msg.id].body = msg.data;
            console.log(msg.data);
        });
      });
      fetch.on('end', function() {
        console.log('Done fetching bodies!');
        cb(undefined, msgCache);

      });
    });
  },
  function(msgs) {
    // Do something here with msgs, which contains the headers and
    // body (parts) of all the messages you fetched
//  console.log(msgs);  
    //imap.logout(cb);  

    imap.on('mail', function () {
        // body...
        console.log("New Email Has Arrived!");
        next = 0;
        cb();
    })


  }
];

cb();

When a new e-mail arrives imap.on('mail', function () I want it to run the cb() function again. However, it doesn't do anything after the console.log.

What am I doing wrong?

Thanks