CentOS(, netinstall, minimal, etc...)
`rpm -q
$ rpm -q postfix
postfix-2.10.1-6.el7.x86_64
$ yum list postfix
postfix.x86_64 2:2.10.1-6.el7 @anaconda
#
postfix.x86_64 2:2.10.1-6.el7 @anaconda
`etc/postfix` tanalab2