갑자기 메일 서버가 안되네요..

밑에 있는 에러 메시지가 발생해요. 어떻게 해야하는지 가르쳐 주세용..

Error Message : 553 5.1.8 <****@****>...
Domain of sender address ****@**** does not
exist

-- You SendMail --

>> Received: from EDUDEP (165.246.191.30)
>> by edu4biz.com (165.246.191.21) with [Nmail V3.2
20020608(S)]
>> for <****@****> from <****@****>;
>> Fri, 18 Jul 2003 13:28:20 +0900
>> From: =?ks_c_5601-1987?B?wLG/tbnM?=
<****@****>
>> To: <****@****>
>> Subject: FW: !Nmail Send error 553 5.1.8
<****@****>... Domain of sender address
****@**** does not exist
>> Date: Fri, 18 Jul 2003 13:17:01 +0900
>> Message-ID:
<****@****>
>> MIME-Version: 1.0
>> Content-Type: text/plain;
>> charset="ks_c_5601-1987"
>> Content-Transfer-Encoding: base64
>> X-Priority: 3 (Normal)
>> X-MSMail-Priority: Normal
>> X-Mailer: Microsoft Outlook IMO, Build 9.0.2416
(9.0.2910.0)
>> Importance: Normal
>> X-MimeOLE: Produced By Microsoft MimeOLE
V6.***-****-****

이런식의 에러 메시지가 발생합니다.. 해결 방법을 가르쳐 주세용..^^