Spring MimeMessageHelper attachment filename encoding

System.setProperty("mail.mime.splitlongparameters", "false");
MimeMessage message = sender.createMimeMessage();
MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8");

// Your email content
helper.setFrom("...");
helper.setTo("...");
helper.setSubject("...");
helper.setText("...");

helper.addAttachment(
    MimeUtility.encodeWord(attachmentFilename),
    attachmentConten