1.postfixの設定
# cd /etc/postfix
# vi mail.cf

myhostname = test.p.oni.gr.jp
mydomain = p.oni.gr.jp
myorigin = $myhostname
inet_interfaces = all
mydestination = $myhostname, localhost.$mydomain, localhost
mynetworks_style = subnet
mynetworks = /29, 168.100.0.0/16, 127.0.0.0/8
relay_domains = $mydestination
recipient_delimiter = +
mail_spool_directory = /var/spool/mail

2.sendmailからpostfix

# /etc/init.d/sendmail stop
# chkconfig sendmail off
# chkconfig postfix on
# /etc/init.d/postfix start