아래와 같이 에러 메세지가 나옵니다.
또한 root로 해도 마찬가지 입니다.
 [min@toms min]$ telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 toms.sk ESMTP Sendmail 8.11.6/8.11.6; Sat, 29 Dec 2001 12:12:15 +0900
quit
221 2.0.0 toms.sk closing connection
Connection closed by foreign host.
 [min@toms min]$ telnet 192.168.121.42 25
Trying 192.168.121.42...
telnet: connect to address 192.168.121.42: Connection refused
[min@toms min]$