use the HTML MIME type when setting headers for your email. If you haven’t, it will look something like this:

// Always set content-type when sending HTML email
    $headers = "MIME-Version: 1.0" . "\r\n";
    $headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";

This basically tells the browser to interpret the HTML code with your message body as actual HTML, and not plain text.