Troubleshooting HTML display in Gmail for JavaMail multipart emails

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1

Hey everyone,

I’m having trouble with my Tomcat app’s email system. It’s supposed to send multipart text/HTML emails using JavaMail. The weird thing is, it works fine in Outlook but not in Gmail.

Here’s what’s happening:

  • Outlook shows the HTML version normally
  • If I move it to Outlook’s spam folder, I see the text version
  • Gmail only displays the text version, even though the HTML is there

I’ve checked that the HTML content is actually in the email (since Outlook can see it). But for some reason, Gmail won’t show it.

Does anyone know if I’m missing some special headers or something? I’m using a local SMTP server if that matters.

Here’s a simplified version of my code:

Message msg = new MimeMessage(session);
Multipart multiPart = new MimeMultipart("alternative");

MimeBodyPart textPart = new MimeBodyPart();
textPart.setText(plainText, "utf-8");

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

multiPart.addBodyPart(htmlPart);
multiPart.addBodyPart(textPart);
msg.setContent(multiPart);

// Set other message properties like from, to, subject, etc.

Transport.send(msg);

Any ideas on what I might be doing wrong? Thanks!

2

I’ve encountered similar issues with Gmail’s rendering of multipart emails. One thing to consider is the MIME version header. Ensure you’re setting it explicitly:

msg.setHeader(“MIME-Version”, “1.0”);

Additionally, Gmail sometimes has issues with certain CSS properties in HTML emails. If your HTML content includes complex styling, try simplifying it or using inline styles instead of external stylesheets.

Lastly, check if your local SMTP server is properly configured for DKIM and SPF. Sometimes Gmail’s spam filters can affect how it handles multipart messages. Testing with a different SMTP provider might help isolate the issue.

3

hey bob, have u tried switching the order of ur bodyparts? sometimes gmail can be picky. try adding the textPart first, then htmlPart. also, double-check ur content-type header. some servers are finicky about that. good luck troubleshooting!

4

I’ve dealt with similar Gmail quirks before. One thing that helped me was adding a specific Content-Disposition header to the HTML part:

htmlPart.setHeader(“Content-Disposition”, “inline”);

This sometimes convinces Gmail to display the HTML version. Also, make sure your HTML is well-formed and closes all tags properly. I once spent hours debugging only to find a missing was causing issues.

Another trick: try sending a test email to a different Gmail account. Sometimes Google’s spam algorithms behave differently for emails sent between Gmail accounts. This can help isolate if it’s a content issue or a delivery problem.

If all else fails, you might need to dig into the raw email headers when received in Gmail. Look for any flags or warnings that might give clues about why it’s not rendering as expected.