sendmail 관련error 도움부탁드립니다

아래와 같은 메시가 되돌아 오면서 메일 발송이 안됩니다.

뭐가 문제인지, 아직 초보라서 도저히 해결할수가 없네요

고수님들의 빠른 답변 기다립니다.

----- Original Message -----
From: "Mail Delivery Subsystem" <MAILER-DAEMON>
To: <jyson@i.dwt.co.kr>
Sent: Monday, September 09, 2002 7:42 PM
Subject: Warning: could not send message for past 4 hours


>     **********************************************
>     **      THIS IS A WARNING MESSAGE ONLY      **
>     **  YOU DO NOT NEED TO RESEND YOUR MESSAGE  **
>     **********************************************
>
> The original message was received at Mon, 9 Sep 2002 16:34:24 +1000
> from [165.133.149.141]
>
>    ----- The following addresses had transient non-fatal errors -----
> <Lim_Y_S@jltasia.com>
>
>    ----- Transcript of session follows -----
> 451 <Lim_Y_S@jltasia.com>... jltasia.com: Name server timeout
> Warning: message still undelivered after 4 hours
> Will keep trying until message is 5 days old