如何使用SMTP服务器将签名附加到电子邮件？

Question

如何在android studio中使用smtp服务器在电子邮件正文中添加图片标题和签名。我尝试通过附加文本文件来尝试

public synchronized void sendMail(String subject, String body, String sender, String recipients) throws Exception {
        try{
            MimeMessage message = new MimeMessage(session);
            DataHandler handler = new DataHandler(new ByteArrayDataSource(body.getBytes(), "text/plain"));
            message.setSender(new InternetAddress(sender));
            message.setSubject(subject);
            addAttachment(multipart, "email.txt");
            message.setDataHandler(handler);  // Create the message part
            if (recipients.indexOf(',') > 0)
                message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(recipients));
            else
                message.setRecipient(Message.RecipientType.TO, new InternetAddress(recipients));
            Transport.send(message);
        }catch(Exception e){
        }
    }
    private Multipart multipart = new MimeMultipart();

    private static void addAttachment(Multipart multipart, String filename) throws MessagingException {
        DataSource source = new FileDataSource(filename);
        BodyPart messageBodyPart = new MimeBodyPart();
        messageBodyPart.setDataHandler(new DataHandler(source));
        messageBodyPart.setFileName(filename);
        multipart.addBodyPart(messageBodyPart);
    }