To add domainkeys and SPF records, you can do the following. Please note that on CPanel servers most of the work is done using cpanel during account creation. However, there are times that this was overlooked and/or not properly configured.
There are scripts in /usr/local/cpanel/bin that can install these on a per-user basis:
If you wish to add DomainKeys and SPF for all Cpanel users on your server, execute the following command.
for user in `ls -A /var/cpanel/users` ; do
/usr/local/cpanel/bin/dkim_keys_install $user &&
/usr/local/cpanel/bin/spf_installer $user ; done
This may take a while to run and will bring your server load up depending on the amount of accounts you have on your server. This is normal. Once this is done, you should have DKIM and SPF enabled on all of your existing cPanel accounts