He intentado escribir un código para enviar correos electrónicos utilizando Java. Pero este código no funciona. Cuando se ejecuta el código, se atasca en transport.send (mensaje). Está atascado allí para siempre. Además, no estoy seguro de si el resto del código es correcto o no.

  //first from, to, subject, & text values are set
    public class SendMail {
    private String from;
    private String to;
    private String subject;
    private String text;


    public SendMail(String from, String to, String subject, String text){
        this.from = from;
        this.to = to;
        this.subject = subject;
        this.text = text;
    }

    //send method is called in the end 
    public void send(){

        Properties props = new Properties();
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.smtp.port", "465");

        Session mailSession = Session.getDefaultInstance(props);
        Message simpleMessage = new MimeMessage(mailSession);

        InternetAddress fromAddress = null;
        InternetAddress toAddress = null;
        try {
            fromAddress = new InternetAddress(from);
            toAddress = new InternetAddress(to);
        } catch (AddressException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        try {
            simpleMessage.setFrom(fromAddress);
            simpleMessage.setRecipient(RecipientType.TO, toAddress);
            simpleMessage.setSubject(subject);
                    simpleMessage.setText(text);
            Transport.send(simpleMessage);  // this is where code hangs     
        } catch (MessagingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }       
    }
}