$message .= "
<html>
<head>
<title>Copy of your form submission</title>
</head>
<body>
<table>
<tr>
<td>
"<img src="images/assets/thank_you.png" alt="Thank You" />"
</td>
</tr>
</table>
</div>
</html>
";
if i write
$message .= same image link above ;
it's working. but when i'm writing the image tag into html like above, then not working. can anyone can help?