PHP邮件不发送，没有错误显示

Question

这是php邮件代码

            $to      = 'mymail@mail.com'; 
            $subject = 'the subject'; 
            $message = 'hello'; 
            $headers = 'From: raghu@digiverti.com' . "\r\n" . 
                'Reply-To: mymail@mail.com' . "\r\n" . 
                'X-Mailer: PHP/' . phpversion(); 

               if(mail($to, $subject, $message, $headers))
              { 
                echo "Sent"; 
              }else{ 

              echo "Not Sent";
              print_r(error_get_last()); 

            }

请让我知道如何显示邮件未发送的实际错误