尚未收到发送电子邮件

Question

所以我有这段代码可以发送电子邮件：

public static void main(String[] args) {
    String to = "mycoolreceiveremail@gmail.com";//change accordingly
    String from = "mycoolsenderemail@gmail.com";//change accordingly
    String host = "localhost";//or IP address

    //Get the session object
    Properties properties = System.getProperties();
    properties.setProperty("mail.smtp.host", host);
    properties.put("mail.smtp.auth", "true");
    properties.put("mail.smtp.port", "25");


    Session session = Session.getDefaultInstance(properties,
            new javax.mail.Authenticator() {
        @Override
        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication("mycoolsenderemail@gmail.com", "mycoolsenderpassword");
        }
    });

    //compose the message
    try {
        MimeMessage message = new MimeMessage(session);
        message.setFrom(new InternetAddress(from));
        message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));
        message.setSubject("Ping");
        message.setText("Hello, this is example of sending email  ");

        // Send message
        Transport.send(message);
        System.out.println("message sent successfully....");

    } catch (MessagingException mex) {
        mex.printStackTrace();
    }

}

问题是我设法发送了它（我想），因为打印了消息“消息发送成功...”。但是问题是我没有收到电子邮件。我检查了邮箱。原因可能是什么？