Azure SMTP Service Corrupts Images with Embedded Inline Data

K. Kong 126

I am using the Azure SMTP service that is in public review.

It was working fine until when I discovered today that it modified <img> elements with embedded inline data, for example <img src="data:image/png;xxxxxx">.

The last time it was working for me when I used it was on Feb 19. The first time this problem cropped up when I used it was on Mar 3.

I did not change my application code at all during all this time. If I now just switch provider, to smtp.gmail.com for example, the exact same mail shows the image correctly.

It appears that Azure converts the tag to <img src="cid:cid0">.

I know this service is experimental, but how do I get this to the attention of Microsoft?

K. Kong 126

I can reproduce it with the following data:

<html>
  <body>
    <h1>Test</h1>
    <img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAGQAAABkBAMAAACCzIhnAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAADUExURf8AABniCTcAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAcSURBVFjD7cEBDQAAAMKg909tDwcEAAAAAByoARPsAAFwJuooAAAAAElFTkSuQmCC" />
  </body>
</html>

The above shows an email with a red square of 100px x 100px when sent through smtp.gmail.com. When sent through smtp.azurecomm.net, it is received as:

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head>
<body><h1>Test</h1><img src="cid:cid0"></body></html>

ajkuma 22,436 Reputation points Microsoft Employee

2024-03-06T07:54:28.6+00:00

Thanks for reporting this. I'm discussing on this internally and will get back to you shortly.

Accepted answer

ajkuma 22,436 Reputation points Microsoft Employee

2024-03-06T12:48:20.75+00:00

Edit:

As K. Kong figured out, potential cause: "So there seems to be something wrong with Gmail's web renderer that happened recently."

--

Following-up on this, we were not able to repro the same behavior (either with SDK or SMTP), I have reached out to you privately for additional info.
Just to confirm, did you also try to send by using PowerShell?

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1 additional answer

K. Kong 126 Reputation points

2024-03-06T13:47:59.9533333+00:00

OK, I think I found the problem. It is with Google!

Mails sent to Exchange users - ok.

Mails sent to Gmail, retrieved in gmail.com - not ok

Mails sent to Gmail, retrieved from Outlook via IMAP - ok

Mails sent to Gmail, forwarded to Exchange user - not ok

So there seems to be something wrong with Gmail's web renderer that happened recently.

Sorry for the wild goose chase.
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ajkuma 22,436 Reputation points Microsoft Employee

2024-03-06T18:29:35.3566667+00:00

K. Kong, No worries, thanks for the follow-up and update.
Glad to know that the issue is sorted out.

I have updated my answer. Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to "Accept " the answer.
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