Thread: sending multiPart mail through yahoo mail cause javax.activation.UnsupportedDataTypeException: no object DCH for MIME type multipart/mixed;

It have been long since I asked for help on the forums but latly I have been Struggling with this problem for a couple of days.
read all the forums did all ppl did but no change.
What the H I am doing wrong ?
by the way I am using javamail 5.1 and java 8 and already send text msg so no problem with properties

here is my code

// Get system properties
    Properties properties = System.getProperties();
    // Setup mail server
    properties.put("mail.smtp.starttls.enable", "true");
    properties.put("mail.smtp.host", mailHost);
    properties.put("mail.smtp.user", mailUserName);
    properties.put("mail.smtp.password", mailPassword);
    properties.put("mail.smtp.port", "587");
    properties.put("mail.smtp.auth", "true");
 
    // Get the default Session object.
    Session session = Session.getDefaultInstance(properties);
 
    try{
        // Create a default MimeMessage object.
        MimeMessage message = new MimeMessage(session);
 
        // Set From: header field of the header.
        message.setFrom(new InternetAddress(mD.mailUserName));
 
        // Set To: header field of the header.
        message.addRecipient(Message.RecipientType.TO,new InternetAddress(to));
 
        Multipart multiPart = new MimeMultipart();
        MimeBodyPart textPart = new MimeBodyPart();
        textPart.setText("This is actual message", "text/html; charset=utf-8");
 
        MimeBodyPart htmlPart = new MimeBodyPart();
        htmlPart.setContent(html, "text/html; charset=utf-8");
        multiPart.addBodyPart(textPart);
        multiPart.addBodyPart(htmlPart);
        message.setContent(multiPart);
 
        // Send message
        Transport transport = session.getTransport("smtp");
        transport.connect( mD.mailHost,mD.mailUserName,mD.mailPassword);
 
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        Thread.currentThread().setContextClassLoader( javax.mail.Session.class.getClassLoader() );
        try
        {
            message.setContent(multiPart);
            //transport.sendMessage(message, message.getAllRecipients());
            Transport.send(message, message.getAllRecipients());
        }
        catch (MessagingException e)
        {
            e.printStackTrace();
        }
        finally
        {
            Thread.currentThread().setContextClassLoader(classLoader);
        }
        transport.close();
    }
    catch (MessagingException mex)
    {
        mex.printStackTrace();
    }

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