Update parked-domain-how-to.md

The example DMARC record is not compatible with the example NULL MX record. The change is based on the M3AAWG Protecting Parked Domains Best Common Practices.
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Michael Kennedy 2020-09-26 00:50:35 +01:00 committed by GitHub
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@ -30,6 +30,10 @@ Set DMARC policy to reject mails, but allow reporting to take place. This helps
`_dmarc.example.nl. IN TXT "v=DMARC1; p=reject; rua=mailto:rua@example.nl; ruf=mailto:ruf@example.nl"`
If the domain itself does not receive email (such as when the domain has been configured with NULL MX), then the RUA and RUF must point to another domain that does receive emails, such as:
`_dmarc.example.nl TXT "v=DMARC1; p=reject; rua=mailto:rua@example.net; ruf=mailto:ruf@example.net"
example.nl._report._dmarc.example.net TXT "v=DMARC1"`
## DKIM
When using a wildcard selector to set an empty public key, you indicate that all previously used keys are revoked and must be considered unreliable. You can also use this to explicitly signal that a domain is not configured to use e-mail. However, [according to the RFC](https://tools.ietf.org/html/rfc6376#section-6.1.2) the absence of a selector / public key (e.g. as a result of deleting the entire DKIM resource record) is semantically equal to a resource record with an empty public key. This means that both approaches should be treated similar by the receiving mail server.