I have this class:

public void sendMessage(String subject, String body, String mailTo, String pathToFile) throws MessagingException, IOException {


    log.info("Sending email to: *{}* ", mailTo);

    Session session = Session.getInstance(prop, new Authenticator() {
        @Override
        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication("info", "aT2coZt2UU");
        }

    });

    //log.info("Sending email to1: " + mailTo);

    Message message = new MimeMessage(session);
    message.setFrom(new InternetAddress("[email protected]"));

    message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(mailTo));
    message.setSubject(subject);

    MimeBodyPart mimeBodyPart = new MimeBodyPart();
    mimeBodyPart.setContent(body, "text/html; charset=utf-8");

    Multipart multipart = new MimeMultipart();
    multipart.addBodyPart(mimeBodyPart);

    log.info("pathToFile: *{}* ", pathToFile);

    if (pathToFile != null) {
        MimeBodyPart attachment = new MimeBodyPart();
        attachment.attachFile(pathToFile);
        multipart.addBodyPart(attachment);
    }

    log.info("Setting content");

    message.setContent(multipart);

    log.info("Sending message {} ", message);

    Transport.send(message);


}

I the String message I use:

 + "A equipe da Mystic River App. nn" +
                "  https://www.mystic-river.com";

But I receive the message without line breaks