java SMTPMessage not render textbody

Question

I've got problem with displaying textBody in sent message by SMTPTransport.sendMessage. I've checked topics and thought that it can be problem when I tried to create SMTPMessage. I put in SMTPMessage simple text by variable m.getTextContent() and htmlText. Result is the email message that display only htmlText. Here is code:

    public SMTPMessage createSMTPMessage(EMailMessage m) throws MessagingException, UnsupportedEncodingException {
    Map<String, String> headers = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
    headers.putAll(m.getHeaders());

    // Create a default MimeMessage object.
    SMTPMessage message = new UniMimeMessage(session); // UniMimeMessage extends SMTPMessage

    // Recipient's email ID needs to be mentioned.
    String to = m.getReceiver();
    // Set To: header field of the header.
    if (to != null && to.length() != 0) {
        InternetAddress[] recips = InternetAddress.parse(to, false);
        if (recips.length > 0) {
            message.addRecipient(javax.mail.Message.RecipientType.TO,
                    new InternetAddress(recips[0].getAddress(), recips[0].getPersonal(), charset));
        }
    } else {
        to = headers.get("To");
        if (to != null && to.length() != 0) {

            InternetAddress[] recips = InternetAddress.parse(to, false);
            if (recips.length > 0) {
                message.addRecipient(javax.mail.Message.RecipientType.TO,
                        new InternetAddress(recips[0].getAddress(), recips[0].getPersonal(), charset));
            }

        }
    }
    //remove TO header in order not to add it twice
    headers.remove("To");

    // Set Subject
    String subject = headers.get("Subject");
    message.setSubject(subject,  charset);
    // remove Subject header in order not to add it twice
    headers.remove("Subject");

    for (String key : headers.keySet())
        message.addHeader(key, headers.get(key));

    String returnPath = headers.get("Return-Path");
    if (returnPath != null && returnPath.length() > 0)
        message.setEnvelopeFrom(returnPath);

    Multipart multipart = new MimeMultipart();

    Multipart innerMultipart = new MimeMultipart("alternative");

    MimeBodyPart messageBodyPart = new MimeBodyPart();


    if (m.getTextContent() != null) {
        messageBodyPart.setContent(m.getTextContent(), "text/plain; charset=" + charset);
        innerMultipart.addBodyPart(messageBodyPart);
    }
    messageBodyPart = new MimeBodyPart();

    String htmlText = m.getPreparedText();
    if (htmlText != null) {
        messageBodyPart.setContent(htmlText, "text/html; charset=" + charset);
        innerMultipart.addBodyPart(messageBodyPart);
    }


    messageBodyPart = new MimeBodyPart();
    messageBodyPart.setContent(innerMultipart);
    multipart.addBodyPart(messageBodyPart);

    //fill mimes
    List<MimeBodyPart> parts = m.getMimeBodyParts();
    for (MimeBodyPart part : parts)
        multipart.addBodyPart(part);


    message.setContent(multipart);

    return message;
}

Does any idea why? Thanks