you'll need the usual mail headers (from, to, subject...)
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Content-Transfer-Encoding: quoted-printable
Content-Type: text/html;
charset="ISO-8859-1";
reply-type=original
<html>
<head>
<title>wibble</title>
</head>
<body>
<img src=3Dcid:hello.jpg />
<p>hello world</p>
</body>
</html>
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