在点击电子邮件之前，在显示附件图标的电子邮件中发送内嵌图像？

Question

我使用下面的代码向用户发送电子邮件，它按预期工作。图像显示在电子邮件中的html中。但最近注意到，在点击电子邮件之前，还有一个附件图标。这是一个小问题，但有点烦人。难以理解为什么会发生这种情况以及如何阻止它？有任何想法吗？谢谢。

public static void send(String useremail, String htmlBody,Map<String, String> mapInlineImages, String subject, String internetAddress, String websiteFrom) throws MalformedURLException{
        Properties props = new Properties();
        Session session = Session.getDefaultInstance(props, null);
        String msgBody = "...";
        try {
          Message msg = new MimeMessage(session);
          msg.setFrom(new InternetAddress(internetAddress, websiteFrom));
          msg.addRecipient(Message.RecipientType.TO,new InternetAddress(useremail, "Admin"));
          msg.setSubject(subject);
          msg.setText(msgBody);
        MimeBodyPart messageBodyPart = new MimeBodyPart();
        messageBodyPart.setContent(htmlBody, "text/html");
        Multipart multipart = new MimeMultipart("related");
        multipart.addBodyPart(messageBodyPart);
        if (mapInlineImages != null && mapInlineImages.size() > 0) {
            Set<String> setImageID = mapInlineImages.keySet();
            for (String contentId : setImageID) {
                MimeBodyPart imagePart = new MimeBodyPart();
                imagePart.setHeader("Content-ID", "<" + contentId + ">");
                imagePart.setDisposition(MimeBodyPart.INLINE);
                String imageFilePath = mapInlineImages.get(contentId);
                try {imagePart.attachFile(imageFilePath);
                } catch (IOException ex) {ex.printStackTrace();
                }multipart.addBodyPart(imagePart);}}
        msg.setContent(multipart);
        Transport.send(msg);
        } catch (AddressException e) {} 
        catch (MessagingException e) {} 
        catch (UnsupportedEncodingException e) {}
}

Answer 1

添加imagePart.addHeader("Content-Type", "image/jpeg");