Hi,
I remember I had same problem a while back so I looked up the code in the applicable script for you. I believe this will work:
$sEmail = "joe@smith.com";
$sEmailTitle = "Hi joe";
$sEmailBody = " blablahtml ";
mail($sEmail, "$sEmailTitle", $sEmailBody, "Content-Type: text/html; charset=\"iso-8859-1\"");