When you set up DMARC for your domain, ISPs will start sending reports to the address in your DNS record.

For instance, if you have published a DNS record on "example.com":

v=DMARC1; p=none; rua=mailto:dmarc@example-corp.com

You will receive reports for "example.com" on your "dmarc@example-corp.com". However, "example-corp.com" should be allowed to receive reports for "example.com" to prevent misuse of DMARC. The system which is used for this is called “External domain verification”. "example-corp.com" needs to publish a DNS record to allow this. The record should be published on:

example.com._report._dmarc.example-corp.com

The contents of this record must be exactly:

v=DMARC1

After setting this up, you’ll start receiving reports on dmarc@example-corp.com.

Note: This only applies when you're sending reports to your own addresses. If you're using the custom DMARCReport.com reporting address in your DNS record, this will already be configured for you.