yum install postfix

rpm -e sendmail

alternatives --display mta

/usr/sbin/alternatives --set mta /usr/sbin/sendmail.postfix

vim /etc/postfix/main.cf

myhostname = mail.test.cn

mydomain = test.cn

myorigin = $mydomain

inet_interfaces = all

mydestination = $myhostname,$mydomain

mynetworks = 127.0.0.0/8

relay_domains =

home_mailbox = Maildir/

service postfix start

rpm -qa dovecot

yum -y install dovecot

vim /etc/dovecot.conf

protocols = imap imaps pop3 pop3s

service dovecot start

service saslauthd restart

postmap /etc/postfix/generic

参考：http://blog.csdn.net/ikscher/article/details/9084313

postfix安装及配制教程