DMARC, which stands for Domain-based Message Authentication, Reporting, and Conformance, is a DNS TXT Record that can be published for a domain to control what happens if a message fails when a recipient server can't verify that the message's sender is who they say they are. A published DMARC record basically serves two purposes. First to tell the recipient server to either: Quarantine the message or Reject the message or Allow the message to continue delivery. Second is to send reports to an email address or addresses with data about all the messages seen from the domain.
How to Add DMARC
1. Log into the cPanel
2. Click the Zone Editor icon that is located under the "DOMAINS" section.
3. Click on "Manage" for the domain you want to add the DMARC record. 
4. Click "+ Add Record" then click on "Add "DMARC" Record"
5. Select the parameters that you want the DMARC record to follow.
6. Click "Add Record" to create the record.
