Even if they could reuse a DKIM hash on an email (pretty sure this is unique per email and would fail on a legitimate check), SPF would show its obviously not from Google. So just make sure your email server correctly handles DKIM verification and blocks SPF hard fails, and you’re probably good against this.

I stopped reading when I realised the publisher is a company that sells a product that fixes the supposed problem.

Maybe this is a thing, maybe it isn’t, but I don’t have the resources to go on reading and analyze it.

it would be nice if people didn’t use AI to write their articles.