How dare Yahoo update their DMARC policy without warning the internet community of the potential fallout from doing so. At least, that's what some other folks have said. My take on it is more prosaic. I figure it's your domain name, you're free to do whatever you want with it. Initially, Yahoo made no statement, leaving us interested folks with nothing but our own speculation about why they've implemented this policy change. (They did later post a limited DMARC Help page and then also a more detailed statement explaining the change.) Here's my speculation.