Greetings,
To change the font in email messages you must send HTML. A CSS stylesheet should work as long as it appears in the body (at least for HotMail).
ie.
<html>
<body>
<style type="text/css" rel="stylesheet"><!--
body { font: 10pt verdana; color: navy; background-color: white; }
.bigbold { font: bold 12pt verdana; color: black; }
.italicred { font: italic 10pt verdana; color: darkred; }
--></style>
This is the "body" style.<br>
<span class=bigbold>This is the "bigbold" style><br>
</body>
</html>
If CSS doesn't work you may need to use standard <font> HTML tags.
When sending HTML the text section is always included (it's required) for email clients that don't support HTML. You may simply want to use a message code of the type "Link to HTML" as your text message to prevent having to create two copies of your email.
Regards,
DW