Why Won't My PHP mail() work?

Question

My PHP mail function isn't sending emails. I've checked my php.ini settings and STMP etc. I also used print_r(error_get_last()) and that returns nothing. The same code used to work when I was with a different host so it is almost definitely a settings/ server issue. Any help would be great - Thanks.

   $msg = "Message";
    $msg = wordwrap($msg,70);

    $mail = mail($email,"Email Confirmation",$msg);
        if($mail){
        //Email Sent


            }
            else{
            //Mail Failed

            }