How to add Domainkeys for a domain on a cPanel server?

“DomainKeys” is an anti-spam software application that uses a public key, cryptography to authenticate the sender’s domain. cPanel offers a installer script “domain_keys_installer” using which the DomainKeys can be created and added automatically for a domain.
By default the DomainKeys is not added when the account is created on the server, it has to be added manually. SSH to your server and execute:

/usr/local/cpanel/bin/domain_keys_installer <username>

where, <username> is the username of the domain.
The DomainKey is automatically added in the DNS zone file of the domain located at /var/named/domainname.db file. To add DomainKeys for the existing domains, use the following script

for i in `cat /etc/trueuserdomains | awk '{print $2}'`
do
/usr/local/cpanel/bin/domain_keys_installer $i;
done;