customize email

Hi, is possible to send some bold text in email?
// ** Send simple email ****

$email="info@info.com";

$from="info@info.com";

$msg = "<b>Test!<b/>";

$subject="Email Tester MORE+";

$ret=runner_mail(array('to' => $email, 'subject' => $subject, 'body' => $msg, 'from'=>$from));

if(!$ret["mailed"])

echo $ret["message"];// Put your code here.

$result["txt"] = $params["txt"]." Andata!!";