class SendMail implements ActionListener{
        public void actionPerformed(ActionEvent evt){
            try
            {
                Properties props=new Properties();  //获得系统属性
                props.put("mail.smtp.auth", "true");  //设置身份验证为true
                //创建邮件会话对象，并启动身份验证
                Session session=Session.getDefaultInstance(props,new Authenticator()
                {
                    public PasswordAuthentication getPasswordAuthentication()
                    {
                        return new PasswordAuthentication(usernameField.getText(),
                                passwordField.getText());
                    }
                });
                final Message msg=new MimeMessage(session);
                Address to=new InternetAddress(toField.getText());
                Address from=new InternetAddress(fromField.getText());
                msg.setFrom(from);
                msg.setRecipient(Message.RecipientType.TO, to);
//                msg.setSentDate(new Data());
                msg.setSubject(transferChinese(subjectField.getText()));
                msg.setContent(message.getText(), "GBK");
                //启动线程来处理
                Runnable r=new Runnable(){
                    public void run()
                    {
                        try
                        {
                            Transport.send(msg);
                        }
                        catch(Exception e){
                            e.printStackTrace();
                        }
                    }
                };
                Thread t=new Thread(r);
                t.start();
                message.setText("");
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
        }
    }

props.put("mail.smtp.host","smtp.qq.com");//设置邮件服务器的域名或IP

------解决方案--------------------
private String host = "smtp.qq.com";
props.put("mail.smtp.host", host);
props.put("mail.smtp.auth", "true");
Authenticator auth = new Email_Autherticator();
Session session = Session.getInstance(props, auth);

------解决方案--------------------
楼主给你发站内了