[센드메일관련]다른 사람들이 저희 서버를 통해 메일을 보내는거

누군가가 저희 서버를 통해서 메일을 보내는거 같은데...
또는 저희 도메인을 가지고 보내는건지...

추가사항:센드메일 ( Ver 8.11.6 )

증상1:
한메일에 메일을 보냈더니 리턴되어 돌아오길래 왜 그런지 한메일 관리자에게 메일을 썼더니만... 우리서버에서 스팸이 하루에 몇천통이 와서 리젝트 시켰다고 하네요..

증상2:
매일 아웃룩을 확인하는데.. 스팸이 무자게 많이 들어옵니다... 더군다나 그 스팸을 보낸 사람이 저희 도메인으로 되어 있다는 겁니다. 물론 계정은 이상한거지만.. (예:오빠@abc.com ... )

위와 같은 증상의 원인은 무엇이며.. 관리자로서 해줄수 있는 방법은 어떤게 있을까요...

글을 검색해 본 결과 access파일의 릴레이 기능이 답인듯하여 확인을 했는데 이상없이 되어있는듯 합니다.. (아래 릴레이파일 참조)
고수님들의 도움 기다리겠습니다.
---------------------------------------------
localhost RELAY
127.0.0.1 RELAY
64.14.139.216 REJECT
64.14.139.214 REJECT
link2buy.com REJECT
mail.link2buy.com REJECT
xxx.com REJECT
66.28.153.14 REJECT
noinhibitons.com REJECT
64.124.88.70 REJECT
e-pia.co.kr REJECT
211.39.149.13 REJECT
mail.e-pia.co.kr REJECT
211.39.149.7 REJECT
kotis.net REJECT
203.233.202.35 REJECT
trademail.kotis.net REJECT
61.77.228.44 REJECT
61.73.16.131 REJECT
203.233.204.231 REJECT
2yqs.com REJECT
66.192.182.25 REJECT
66.192.182.26 REJECT
mail.2yqs.com REJECT
savingsengine.com REJECT
216.109.92.220 REJECT
mail1.savingsengine.com REJECT
mail.savingsengine.com REJECT
216.109.92.221 REJECT
emza.net REJECT
216.216.0.131 REJECT
216.109.92.210 REJECT
209.19.106 REJECT
63.251.59.71 REJECT
mx-003.etracks.com REJECT
response.etracks.com REJECT
mx-001.etracks.com REJECT
209.19.106.20 REJECT
209.19.106.6 REJECT
209.19.106.81 REJECT
big@boss.com REJECT
haruya.co.jp REJECT
and.groupsystem.net REJECT
sex@ REJECT
-------------------------------------------------------------

PS.
참고로 밑에 답글주신분의 말씀대로 테스트를 해봤습니다.
결과물은 다음과 같은데... 이상이 없다는 건지 이상있다는 건지...
--------------------------------------------------------
[root@Mail mail]# telnet relay-test.mail-abuse.org
Trying 168.61.4.13...
Connected to relay-test.mail-abuse.org.
Escape character is '^]'.
Connecting to 218.234.xx.xxx ...
<<< 220 xxxxx.co.kr ESMTP Sendmail 8.11.6/8.11.6; Tue, 13 Apr 2004 17:33:42 +0900
>>> HELO cygnus.mail-abuse.org
<<< 250 xxxxx.co.kr Hello Cygnus.mail-abuse.org [168.61.4.13], pleased to meet you
:Relay test: #Quote test
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 1
>>> mail from: <nobody@mail-abuse.org>
<<< 250 2.1.0 <nobody@mail-abuse.org>... Sender ok
>>> rcpt to: <nobody@mail-abuse.org>
<<< 550 5.7.1 <nobody@mail-abuse.org>... Relaying denied
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 2
>>> mail from: <spamtest@maps1.pa.vix.com>
<<< 250 2.1.0 <spamtest@maps1.pa.vix.com>... Sender ok
>>> rcpt to: <nobody@mail-abuse.org>
<<< 550 5.7.1 <nobody@mail-abuse.org>... Relaying denied
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #test 3
>>> mail from: <spamtest@localhost>
<<< 553 5.3.0 <spamtest@localhost>... Unknown User
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 4
>>> mail from: <spamtest>
<<< 553 5.5.4 <spamtest>... Domain name required for sender address spamtest
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 5
>>> mail from: <>
<<< 250 2.1.0 <>... Sender ok
>>> rcpt to: <nobody@mail-abuse.org>
<<< 550 5.7.1 <nobody@mail-abuse.org>... Relaying denied
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 6
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 7
>>> mail from: <spamtest@[218.234.37.130]>
<<< 250 2.1.0 <spamtest@[218.234.37.130]>... Sender ok
>>> rcpt to: <nobody@mail-abuse.org>
<<< 550 5.7.1 <nobody@mail-abuse.org>... Relaying denied
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 8
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 9
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 10
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 11
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 12
>>> mail from: <spamtest@[218.234.37.130]>
<<< 250 2.1.0 <spamtest@[218.234.37.130]>... Sender ok
>>> rcpt to: <nobody@mail-abuse.org@">
<<< 553 5.0.0 Unbalanced '"'
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 13
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 14
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 15
>>> mail from: <spamtest@[218.234.37.130]>
<<< 250 2.1.0 <spamtest@[218.234.37.130]>... Sender ok
>>> rcpt to: <@:nobody@mail-abuse.org>
<<< 550 5.7.1 <@:nobody@mail-abuse.org>... Relaying denied
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 16
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #Test 17
>>> mail from: <spamtest@[218.234.37.130]>
<<< 250 2.1.0 <spamtest@[218.234.37.130]>... Sender ok
>>> rcpt to: <mail-abuse.org!nobody>
<<< 550 5.7.1 <mail-abuse.org!nobody>... Relaying denied
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #test 18
>>> mail from: <spamtest@>
<<< 553 5.5.4 <spamtest@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
:Relay test: #test 19
>>> mail from: <postmaster@>
<<< 553 5.5.4 <postmaster@>... Domain name required for sender address
>>> rset
<<< 250 2.0.0 Reset state
>>> QUIT
<<< 221 2.0.0 xxxxx.co.kr closing connection
Tested host banner: 220 xxxxx.co.kr ESMTP Sendmail 8.11.6/8.11.6; Tue, 13 Apr 2004 17:33:42 +0900
System appeared to reject relay attempts
Connection closed by foreign host.
---------------------------------------------------------------