无法连接到SMTP主机：smtp8.net4india.com，端口：25；

Question

While sent email showing error:

javax.mail.MessagingException: Could not connect to SMTP host: smtp8.net4india.com, port: 25;
  nested exception is:
    java.net.ConnectException: Connection timed out: connect

My email settings is:

        String mailProcessed = "";
        Properties props = new Properties();
        props.put("mail.smtp.host", "smtp8.net4india.com");
        props.put("mail.smtp.socketFactory.port", "25");
        props.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", "25");
        props.put("mail.smtp.starttls.enable", "true");

        Session session = Session.getDefaultInstance(props,
                new javax.mail.Authenticator() {
                    protected PasswordAuthentication getPasswordAuthentication() {
                        return new PasswordAuthentication(frmMail, frmPass);
                    }
                });

Answer 1

remove props.put("mail.smtp.starttls.enable", "true");

and add props.put("mail.smtp.ssl.enable", "true");

You are using SSL, not TLS.

Also make sure the mail server supports SSL.

Also make sure that the mail server is using TCP protocol SMTP , they might be using IMAP or POP3 . In that case you need to change the properties you reference by the protocol they use, ie: props.put("mail.pop3.socketFactory.port", "25"); props.put("mail.pop3.socketFactory.class","javax.net.ssl.SSLSocketFactory");

You are using getDefaultInstance for the session, but if a session was already established it will return the existing session and your properties will be lost.

Check the common mistakes page, it has it all: https://javaee.github.io/javamail/FAQ#commonmistakes