How to authenticate your domain
DKIM enabling on Postfix Server
#rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm (Copy this repo file from local PC and install accordingly. Also check for proxyconnection whether enabled) #yum install opendkim #yum install opendkim-tools #cd /etc/opendkim/keys/ #ls #mkdir “Domain_Name”