2. Click Advanced DNS Zone Editor under the Domains section.

 3. Then select the domain name that you need to modify.

 4. Under Add a Record, set the following values.

Type : TXT

TTL : 14000

Name : _dmarc (Please note cPanel will automatically append the domain name for you)

TXT Data :  You can add any of the following (or other) example configurations:

v=DMARC1;p=quarantine;pct=100; (It will instruct the recipient to quarantine all messages which do not pass this policy check)
​ v=DMARC1;p=reject;pct=50; (It will instruct the recipient to reject half of all messages)

 5. Once it is done, click Add Record.