초당 3~5통의 아래와 같은 메일이 보내지는데 해킹인지

초당 3~4개씩 계속 루트에게 전달되는 메일이 있습니다.
릴레이는 잠궈놨는데.... 보낼수는 없을것같고 어떤 의미
인지 잘 모르겠습니다. 이런 일이 처음이라서요...
어떻게해야 할까요?

아래는 계속되는 메일중 1개
-----------------------------------------------------------------
Date: Thu, 1 May 2003 01:12:15 +0900
From: Mail Delivery Subsystem <MAILER-DAEMON@w3.kyongbuk.co.kr>
To: postmaster@w3.kyongbuk.co.kr
Subject: Postmaster notify: see transcript for details
Auto-Submitted: auto-generated (postmaster-notification)

[-- 첨부물 #1 --]
[-- 종류: text/plain, 인코딩 방식: 7bit, 크기: 0.6K --]

The original message was received at Thu, 1 May 2003 01:12:13 +0900
from localhost
with id h3UGCDka030669

   ----- The following addresses had permanent fatal errors -----
<1j17i.yyy3j@yahoo.com>
    (reason: 554 delivery error: dd This user doesn't have a yahoo.com account (1j17i.yyy3j@yahoo.com) [0] -
+mta203.mail.scd.yahoo.com)

   ----- Transcript of session follows -----
... while talking to mx2.mail.yahoo.com.:
>>> DATA
<<< 554 delivery error: dd This user doesn't have a yahoo.com account (1j17i.yyy3j@yahoo.com) [0] - mta203.mail.scd.yahoo.com
554 5.0.0 Service unavailable

[-- 첨부물 #2 --]
[-- 종류: message/delivery-status, 인코딩 방식: 7bit, 크기: 0.4K --]

Reporting-MTA: dns; w3.kyongbuk.co.kr
Received-From-MTA: DNS; [192.168.1.1]
Arrival-Date: Thu, 1 May 2003 01:12:13 +0900

Final-Recipient: RFC822; 1j17i.yyy3j@yahoo.com
Action: failed
Status: 5.0.0
Remote-MTA: DNS; mx2.mail.yahoo.com
Diagnostic-Code: SMTP; 554 delivery error: dd This user doesn't have a yahoo.com account (1j17i.yyy3j@yahoo.com) [0] -
+mta203.mail.scd.yahoo.com
Last-Attempt-Date: Thu, 1 May 2003 01:12:15 +0900

[-- 첨부물 #3 --]
[-- 종류: message/rfc822, 인코딩 방식: 7bit, 크기: 9.6K --]
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