Install postfix
yum install postfix
Remove sendmail
/etc/init.d/sendmail stop
yum remove sendmail sendmail-cf
Start postfix
/etc/init.d/postfix start
chkconfig postfix on
Configuration
vim /etc/postfix/main.cf
myhostname = www.my-helper.com
myorigin = $myhostname
Restart postfix
/etc/init.d/postfix check
/etc/init.d/postfix restart
netstat -tlunp | grep :25