如何使用Message.writeTo将电子邮件另存为.eml与X-Unsent：1

Question

我希望将电子邮件保存为带附件的.eml格式。我能够保存.eml，但是当我打开它时，它应该以草稿格式打开，用户应该能够从，输入，主题和编辑电子邮件正文。我必须手动编辑保存的.eml文件以添加X-Unsent：1以显示为草稿。我怎样才能在代码中实现这一点，mimeMessage的哪些属性可以帮助我做到这一点？

public static void createMessage(String to, String from, String subject, String body, List<File> attachments) {
try {
    Message message = new MimeMessage(Session.getInstance(System.getProperties()));
    message.setFrom(new InternetAddress(from));
    message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
    message.setSubject(subject);
    // create the message part 
    MimeBodyPart content = new MimeBodyPart();
    // fill message
    content.setText(body);
    Multipart multipart = new MimeMultipart();
    multipart.addBodyPart(content);
    // add attachments
    for(File file : attachments) {
        MimeBodyPart attachment = new MimeBodyPart();
        DataSource source = new FileDataSource(file);
        attachment.setDataHandler(new DataHandler(source));
        attachment.setFileName(file.getName());
        multipart.addBodyPart(attachment);
    }
    // integration
    message.setContent(multipart);
    // store file
    message.writeTo(new FileOutputStream(new File("c:/mail.eml")));
} catch (MessagingException ex) {
    Logger.getLogger(Mailkit.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
    Logger.getLogger(Mailkit.class.getName()).log(Level.SEVERE, null, ex);
}

}

Answer 1

如何添加此行：

 message.setHeader("X-Unsent", "1");