DKIM helps verify the sender and integrity of a message.
It allows an email system to prove that a message was not altered during transit (meaning it is not forged), and that the message came from the specified domain.
To enable DKIM within WHM/cPanel
1. Login to cPanel account,
2. Once logged in, click on "Email Authentication",
3. To use DKIM, click Enable.
4. To disable DKIM, click Disable.
5. Scroll down to the bottom and click "Update",
Note: If a warning is displayed claiming cPanel is unable to verify that the server is an authoritative nameserver for the specified domain name and either of the following scenarios is true, then please ignore it.
-The server has been changed to be the authoritative DNS server for the domain name, but the change has not yet propagated.
-The server does not view itself as the authoritative DNS server, but outside servers do view it as authoritative.