Problema com envio de mail

import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class Mail {

    public void enviar(String assunto, String de, String para, String mensagem) throws AddressException,
	    MessagingException {

	Properties properties = new Properties();

	properties.put("mail.smtp.host", "smtp.google.com");
	properties.put("mail.smtp.auth", "true");

	AutenticadorSmtp autenticadorSmtp = new AutenticadorSmtp();
	Session mailSession = Session.getDefaultInstance(properties, autenticadorSmtp);

	InternetAddress remetente = new InternetAddress(de);
	InternetAddress destinatario = new InternetAddress(para);

	Message message = new MimeMessage(mailSession);
	message.setFrom(remetente);
	message.setRecipient(Message.RecipientType.TO, destinatario);
	message.setSubject(assunto);
	message.setContent(mensagem, "text/html");

	Transport.send(message);
    }

    public static void main(String args[]) throws AddressException,
	    MessagingException {
	Mail mail = new Mail();
	
	mail.enviar("meu assunto", "[email removido]", "[email removido]", "Foi!");
    }
}

import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;

public class AutenticadorSmtp extends Authenticator {
    public PasswordAuthentication getPasswordAuthentication() {
	String username = "[email removido]";
	String password = "********";
	return new PasswordAuthentication(username, password);
    }
}