1、安裝postfix
# yum install postfix
# rpm -e sendmail
2、配置postfix
# postconf -n > /etc/postfix/main2.cf
# mv /etc/postfix/main.cf /etc/postfix/main.cf.old
# mv /etc/postfix/main2.cf /etc/postfix/main.cf
3、編輯main.cf：
# vi /etc/postfix/main.cf
增加如下內容：
# hostname
mynetworks = 127.0.0.1
myhostname = mail.extmail.org
mydestination = $mynetworks $myhostname
# banner
mail_name = Postfix - by extmail.org
smtpd_banner = $myhostname ESMTP $mail_name
# response immediately
smtpd_error_sleep_time = 0s
# Message and return code control
message_size_limit = 5242880
mailbox_size_limit = 5242880
show_user_unknown_table_name = no
# Queue lifetime control
bounce_queue_lifetime = 1d
maximal_queue_lifetime = 1d
4、設置postfix開機自啓：
# netstat -n -a –tcp
# chkconfig postfix on