Here are some generic instructions on how to add a "_dmarc." record in DNS as a TXT record:
- Log in to the control panel of your DNS provider.
- Select the domain name you want to add the "_dmarc." record to.
- Look for the option to add a new record and select TXT record type.
- In the "Name" field, enter "_dmarc" (without quotes).
- In the "Value" or "Text" field, paste your DMARC record (example: "v=DMARC1; p=none; rua=mailto:firstname.lastname@example.org").
- Save your changes.
Wait for the DNS changes to propagate, which can take up to 24-48 hours.
Note that the exact steps may vary depending on your DNS provider's interface, but the basic process should be similar. Also, make sure to use the correct syntax for the DMARC record in the "Value" field, as DMARC has a specific syntax that must be followed for it to function correctly.