In these repositories you will find packages for the latest Postfix releases and a few other packages for CentOS and Red Hat Enterprise Linux 5, 6 and 7. These packages are not part of the upstream distribution and extend your Enterprise Linux functionality at the expense of upstream compatibility. To enable one of the repositories, add the file /etc/yum.repos.d/postfix.repo and add the following lines: [postfixrepo] name=EL-$releasever Postfix repo baseurl=https://repos.oostergo.net/$releasever/postfix- enabled=1 gpgcheck=1 To import the public key used for signing, use the following command: su -c 'rpm --import https://repos.oostergo.net/RPM-GPG-KEY' You would also want to add the following line to the [base] and [update] sections of /etc/yum.repos.d/CentOS-Base.repo to exclude postfix packages from the default repository. exclude=postfix-*