javax.net.ssl.SSLException：无法识别的SSL消息，使用JAVA从Zimbra发送邮件时的纯文本连接

Question

如果我尝试从java发送邮件，我收到以下错误。我们有Zimbra邮件服务器。

[java] javax.mail.MessagingException: Exception reading response;
[java]   nested exception is:
[java]     javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?

以下是我的代码：

public class SSLEmail {

    public void sendMail(){
            final String fromEmail = "test@mydomain.com"; //requires valid gmail id
            final String password = "test"; // correct password for gmail id
            final String toEmail = "test2@gmail.com"; // can be any email id 

            Properties props = new Properties();
            props.put("mail.smtp.username", fromEmail);
            props.put("mail.smtp.password", password);
            props.put("mail.smtp.protocol", "smtp");
            props.put("mail.smtp.host", "mail.hostname.com");
            props.put("mail.smtp.port", "587");
            props.put("mail.smtp.auth", "true");
            props.put("mail.smtp.socketFactory.port", "587");
            props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
            props.put("mail.smtp.socketFactory.fallback", "true");

            Authenticator auth = new Authenticator() {
                //override the getPasswordAuthentication method
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(fromEmail, password);
                }
            };

            Session session = Session.getDefaultInstance(props, auth);
            session.setDebug(true);
            System.out.println("Session created");
                EmailUtil.sendEmail(session, toEmail,"SSLEmail Testing Subject", "SSLEmail Testing Body");
    }

}



public class EmailUtil {

    public static void sendEmail(Session session, String toEmail, String subject, String body){
        try
        {
          MimeMessage msg = new MimeMessage(session);
          //set message headers
          msg.addHeader("Content-type", "text/HTML; charset=UTF-8");
          msg.addHeader("format", "flowed");
          msg.addHeader("Content-Transfer-Encoding", "8bit");

          msg.setFrom(new InternetAddress("test@mydomain.com"));

          msg.setSubject(subject, "UTF-8");

          msg.setText(body, "UTF-8");

          msg.setSentDate(new Date());

          msg.setRecipients(Message.RecipientType.TO, InternetAddress.parse(toEmail));
          Transport.send(msg);  
        }
        catch (Exception e) {
          e.printStackTrace();
        }
    }
}