图片一：
步骤一：
步骤二：【操作前请先看步骤一】安装epel源，理论上处理过步骤二就不需要步骤三了
1、yum -y install epel-release
2、rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm步骤三：【操作前请先看步骤一】如已存在被禁用请按此操作开启，理论上处理过步骤二就不需要步骤三了首先创建并编辑/etc/yum.repos.d/epel.repo
vi /etc/yum.repos.d/epel.repo
并将以下内容放进去
[epel]
name=Extra Packages for Enterprise Linux 7 - $basearch
#baseurl=http://download.fedoraproject.org/pub/epel/7/$basearch
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=$basearch
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
[epel-debuginfo]
name=Extra Packages for Enterprise Linux 7 - $basearch - Debug
#baseurl=http://download.fedoraproject.org/pub/epel/7/$basearch/debug
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-debug-7&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
gpgcheck=1
[epel-source]
name=Extra Packages for Enterprise Linux 7 - $basearch - Source
#baseurl=http://download.fedoraproject.org/pub/epel/7/SRPMS
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-source-7&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
gpgcheck=1
‘ESC’键->‘Shift’键+‘:’键->‘W’键->‘Q’键->‘Enter’键，然后执行：
1、yum clean
2、yum makecache
3、yum repolist all
这个时候一般epel就是启用的了，就可以安装opendkim了
yum install opendkim -y
等安装好了再打开邮局系统就可以会显示出default._domainkey的txt记录了
