code: function Mailer(opts) {
  	opts = opts || {};
  	var smtp = opts.smtp;
  	if(!smtp) { throw new TypeError("bad arguments"); }
  	this._transport = nodemailer.createTransport("SMTP", smtp);
  	this._transport_sendMail = Q.nbind(this._transport.sendMail, this._transport);
  	this._transport_close = Q.nbind(this._transport.close, this._transport);
  }
docs: The sending of an email message