DNS and Domains not used for email

Updated Jan 2022 - Added Cloudflare note on protectingdomains without email.

See Gov.UK article

And Ryan Castelluci on Twitter

If you have domains that you’re not using for email, please set up DNS records to prevent spammers from using them.

. TXT "v=spf1 -all"
. MX . 0
_dmarc.       TXT "v=DMARC1;p=reject;sp=reject;adkim=s;aspf=s"
*._domainkey. TXT "v=DKIM1; p="