php 메일 보내기

if($mode == 'admin') {//관리자가 답변을 달 경우에는 입력한 사람한테 메일이 간다.
$footer = "</body></html>";
$outcontent= $outcontent.$footer;
$outsubject = "[고객게시판]".$subject;
mail( $mailto, $outsubject, $outcontent, $mail_header );
$list_pgm = recruit3.php";
$manager='Y';

//관리자가 답변을 달 경우에는 입력한 사람한테 메일이 가도록 만들었습니다.
그리구
$mailto, $outsubject, $outcontent, $mail_header 를 출력도 도 해봤는데
다 나오고요

리눅스 서버에서 sendmail이 동작하고 있구요
mail log을 분석해보니 이렇게 나와요
오늘 하루종일 했는데 해결이 안돼용 뭐가 문제 인가요

Jul 17 16:10:49 ns sendmail[26595]: m6H7AnJh026595: from=daemon, size=157, class=0, nrcpts=1, msgid=<200807170710.m6H7AnJh026595@ph.co.kr>, relay=daemon@localhost
Jul 17 16:10:49 ns sendmail[26595]: m6H7AnJh026595: to=0828@ph.co.kr, ctladdr=daemon (2/2), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30040, relay=localhost.co.kr. [211.115.215.71], dsn=5.7.1, stat=User unknown
Jul 17 16:10:49 ns sendmail[26595]: m6H7AnJh026595: m6H7AnJi026595: DSN: User unknown
Jul 17 16:10:49 ns sendmail[26595]: m6H7AnJi026595: to=daemon, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31181, relay=localhost.co.kr. [211.115.215.71], dsn=5.7.1, stat=User unknown
Jul 17 16:10:49 ns sendmail[26595]: m6H7AnJi026595: m6H7AnJj026595: return to sender: User unknown
Jul 17 16:10:50 ns sendmail[26595]: m6H7AnJj026595: to=postmaster, delay=00:00:01, xdelay=00:00:00, mailer=relay, pri=32205, relay=localhost.co.kr. [211.115.215.71], dsn=5.7.1, stat=User unknown
Jul 17 16:10:50 ns sendmail[26595]: m6H7AnJi026595: Losing ./qfm6H7AnJi026595: savemail panic
Jul 17 16:10:50 ns sendmail[26595]: m6H7AnJi026595: SYSERR(daemon): savemail: cannot save rejected email anywhere