How does “External Domain Verification” work

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 ‘somedomainyouown.com’:
v=DMARC1; p=none; rua=mailto:dmarc@corporatedomain.com
You will receive reports for ‘somedomainyouown.com’ on your ‘dmarc@corporatedomain.com’. However, ‘corporatedomain.com’ should be allowed to receive reports for ‘somedomainyouown.com’ to prevent misuse of DMARC. The system which is used for this is called “External domain verification”. ‘Corporatedomain.com’ needs to publish a DNS record to allow this. The record should be published on:
somedomainyouown.com._report._dmarc.corporatedomain.com
The contents of this record must be exactly:
v=DMARC1
After setting this up, you’ll start receiving reports on dmarc@corporatedomain.com!
Please note this only applies when you’re sending reports to your own addresses. If you’re using the custom DMARC Analyzer report address in your DNS record, you’re all set! We already configured this for you.