Must issue a STARTTLS command first. mail.smtp.EnableSSL.enable already set to true

Question

I am working on Java Spring, Maven and I am trying to send a mail on gmail, using a gmail id. I am getting this error:

com.sun.mail.smtp.SMTPSendFailedException: 530 5.7.0 Must issue a STARTTLS command first. 11sm885884pfp.38 - gsmtp

even through I have set the parameter

mail.smtp.starttls.enable

to true.

This is my function:

public String sendMail(String to, String subject, String textMessage) throws IOException {
    Properties props = new Properties();
    props.put("mail.transport.protocol", "smtp");
    props.put("mail.smtp.starttls.enable", "true");
    props.put("mail.smtp.host", "smtp.gmail.com");
    props.put("mail.smtp.auth", "true");
    Session mailSession = Session.getInstance(props);
    mailSession.setDebug(true);
    Message simpleMessage = new MimeMessage(mailSession);

    InternetAddress fromAddress = from@gmail.com;
    InternetAddress toAddress = null;
    try {
        toAddress = new InternetAddress(to);
    } catch (AddressException e) {
        System.out.print("\nError in Address of Sender or reciever\n");
        e.printStackTrace();
    }
    try {
        simpleMessage.setFrom(fromAddress);
        simpleMessage.setRecipient(RecipientType.TO, toAddress);
        simpleMessage.setSubject(subject);
        simpleMessage.setText(textMessage);
        SMTPTransport t = (SMTPTransport) mailSession.getTransport("smtp");
        t.setStartTLS(true);
        t.connect("smtp.gmail.com", "from@gmail.com", "from.password!");
        t.sendMessage(simpleMessage, simpleMessage.getAllRecipients());
        t.close();

    } catch (MessagingException e) {             
        System.out.print("\nError in message Genration\n");
        e.printStackTrace();
    }
    return "success";
}

All the answers on SO tell us to set mail.smtp.starttls.enable to true. Doing that even does not work.

I have also included the javax.mail dependency in my pom as:

<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
    <version>1.4</version>
</dependency>

Answer 1

When you're using spring, it's better to incorporate their abstractions instead of javax.mail low level API. In fact, you can use JavaMailSender and its implementation, JavaMailSenderImpl, to achieve the same result. See this for an example.