DomainKeys, similar to SPF records, authenticate that an email was sent from an authorized sender. Several mail services such as Hotmail and Yahoo have started requiring these…luckily they are easy to set up in your cPanel.
1. cPanel/WHM v11.x with the latest build
2. Your Mail server must be using Maildir format and NOT Mbox.
To install for a single user:
If you get an error such as: “Domain keys are not installed on this machine.” your server didn’t meet system requirement mentioned above.
To install DomainKeys for all accounts on a server:
for i in `ls /var/cpanel/users` ;do /usr/local/cpanel/bin/domain_keys_installer $i; done
Do NOT interrupt or stop the process until completed.