한메일에 전송이 실패하네요

에러 메시지입니다.

>> Received: from zzang (61.126.24.xxx)
>> by () with [Nmail V3.3 20021108(S)]
>> for <****@****> from <****@****_name.co.kr>;
>> Mon, 25 Apr 2005 11:53:00 +0900
>> From: =?ks_c_5601-1987?B?v8DA57vv?= <****@****_name.co.kr>
>> To: <****@****>
>> Subject: 1158
>> Date: Mon, 25 Apr 2005 11:58:32 +0900
>> MIME-Version: 1.0
>> Content-Type: multipart/related;
>> boundary="----=_NextPart_000_000A_01C5498E.1C8D1980"
>> X-Mailer: Microsoft Office Outlook, Build 11.0.5510
>> Thread-Index: AcVJQqprPsqyPWApStG35c8AluqNCA==
>> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.181


C:\Documents and Settings\Administrator>nslookup -type=mx domain_name.co.kr ns.da
um.net
Server: ns.daum.net
Address: 211.32.117.10

Non-authoritative answer:
samanworld.co.kr MX preference = 10, mail exchanger = mail.domain_name.co.
kr

mail.domain_name.co.kr nameserver = ns.mail.domain_name.co.kr
mail.domain_name.co.kr nameserver = ns.mail.domain_name.co.kr
mail.domain_name.co.kr internet address = 61.126.24.247


이런식으로 다 나오고 1차 dns 2차 dns모두 신호 갑니다. 설정도 맞구요..
근데 위와 같이 메시지가 오면서 다음에만 안가네요..왜 그럴까요..