nslookup
set q=mx
example
to ensure the mail server is ready


add MX　ｔｏ　ｅｘａｍｐｌｅ．ｃｏｍ．ｚｏｎｅ　ａｎｄ　１９２．１６８．１．ｚｏｎｅ
ｒｎｄｃ　ｒｅｌｏａｄ

ｅｎｓｕｒｅ　ｐｏｒｔ２５　ｉｓ　ｏｐｅｎ　（ｓｍｔｐ）　ｉｎ　ｂｏｔｈ　ｓｅｎｄ　ａｎｄ　ｒｅｃｉｅｐｉｅｎｔ．
ｎｍａｐ　ｌｏｃａｌｈｏｓｔ　ｔｏ　ｃｈｅｃｋ

ｉｎｓｔａｌｌ　ｐｏｓｔｆｉｘ　ａｎｄ　ｓｅｎｄｍａｉｌ　ｔｏ　ｅｎｓｕｒｅ　ｔｈｅ　ｐｏｒｔ２５　ｉｓ　ｏｐｅｎ
ｙｕｍ　ｉｎｓｔａｌｌ　ｓｙｓｔｅｍ－ｓｗｉｔｃｈ－ｍａｉｌ

ｓｅｎｄｍａｉｌ．ｍｃ　ｍｕｓｔ　ｂｅ　ｄｎｌ　１２７．０．０．１
ｕｎ　ｄｎｌ　ｔｏ　ｅｎａｂｌｅ　ｉｐｖ４　ａｎｄ　ｉｐｖ６　ｔｏ　ｓｅｎｄｍａｉｌ

ｍ４　ｓｅｎｄｍａｉｌ．ｍｃ　＞　ｓｅｎｄｍａｉｌ．ｃｆ

ｖｉ　／ｅｔｃ／ｍａｉｌ／ｌｏｃａｌ－ｈｏｓｔ－ｎａｍｅ
ｓｅｒｖｅｒ．ｅｘａｍｐｌｅ．ｃｏｍ

ｖｉ　／ｅｔｃ／ｍａｉｌ／ａｃｃｅｓｓ
１９２．１６８．１．　ｒｅｌａｙ

ｖｉ　／ｅｔｃ／ａｌｉａｓｅｓ
ｎｅｗａｌｉａｓｅ

ｍａｋｅ　－Ｃ　／ｅｔｃ／ｍａｉｌ

ｓｅｎｄ　ｔｏ　ｍａｉｌ　ｓｅｒｖｅｒ　ｗｉｌｌ　ｗｏｒｋ　ｗｈｉｌｅ　ｓｅｎｄ　ｔｏ　ａｃｃｏｕｎｔ　ｏｎ　ｏｔｈｅｒ　ｍａｃｈｉｎｅ　ｏｎ　ｔｈｅ　ｌａｎ　ｉｓ　ｎｏｔ　ｗｏｒｋｉｎｇ
ｓｕｃｈ　ａｓ　　ｍａｉｌ　ｘｉｎｇ＠ｓｅｒｖｅｒ．ｅｘａｍｐｌｅ．ｃｏｍ　　　ｏｋ
　　　　　　　　ｍａｉｌ　ｘｉｎｇ＠ｃｌｉｅｎｔ．ｅｘａｍｐｌｅ．ｃｏｍ　　ｎｏ　ｍａｉｌ　ｗｉｌｌ　ｂｅ　ｒｅｃｅｉｖｅｄ
#block mails from example.com ,relay mails from 192.168.0.0/24
vi /etc/mail/access
192.168.0  relay
@example.com   reject
 
#mails going from LAN masquerate as example.com
vi /etc/mail/sendmail.mc
MASQUERADE_AS('example.com')dnl
 
#any incoming mail for info@example.com vitual address should be map to adm@example.com
vi /etc/mail/virtusertable
 
#All outgoing mail should be sent via smpt.abc.com mail server
vi /etc/mail/sendmail.mc
define('SMART_HOST','smtp.abc.com')
 
#All mails to example.com should get by xing user
vi /etc/mail/virtusertable
@example.com  xing
service sendmail restart
chkconfig sendmail on
 
#All mails coming for accountmanager should get by xing
vi /etc/mail/virtusertable
accountmanager@  xing

------------------
test email
[root@station15 mail]# telnet 192.168.0.6 25
Trying 192.168.0.6...
Connected to station6.example.com (192.168.0.6).
Escape character is '^]'.
220 station6.example.com ESMTP Sendmail 8.13.8/8.13.8; Sun, 31 Oct 2010 16:41:38 +0800
helo station6
250 station6.example.com Hello station15.example.com [192.168.0.15], pleased to meet you
mail from:root@station6.example.com
250 2.1.0 root@station6.example.com... Sender ok
rcpt to:root@station15.example.com
250 2.1.5 root@station15.example.com... Recipient ok
data
354 Enter mail, end with "." on a line by itself
this is test.
.
250 2.0.0 o9V8fcLC006097 Message accepted for delivery
quit
221 2.0.0 station6.example.com closing connection
Connection closed by foreign host.

------
check if the email received.
/var/spool/mail/root
-------