DKIM, DMARC, DNSSEC, SPF and Subdomains | by Teri Radichel | Cloud Security | Aug, 2025

If you apply the security to your top level domain does it apply to the subdomain?

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Sorry I haven’t written for a while. Been busy and AI is kind of a drag for writers, but I have a lot of things I want to write about anyway when I get the chance.

For today, I was helping someone with a follow up on a pentest and an interesting question came up. When you configure DKIM, DMARC, DNSSEC and SPF for a top level domain, does that apply to all the subdomains?

I thought I’d just write it down for anyone else who needs to know. First of all, if you need to know how to configure those in the first place I wrote about all that and how to test it here: