You can install domain keys on a cPanel server easily for a single domain, in this tutorial I am using cPanel 11.
Run the following command shown below:

[root@afrizal etc]# /usr/local/cpanel/bin/domain_keys_installer username
(i.e.: /usr/local/cpanel/bin/domain_keys_installer afrizal)
It will automatically installing Domain Key for the domain (afrizal.net) successfully.
Now you can verify it from the db record of the domain. The following [...]