All this talk about Yahoo's recent DMARC policy change got a friend to ask me about her domain name and whether or not this change has any impact on her.
Ellen asked me, "Does this mean anyone with a personal domain sending through an ISP who implements DMARC with a p=reject policy is going to have problems if they try to send mail to any recipient who checks DMARC?"
Thankfully, the answer is no, it shouldn't cause any problems for you when you send mail using your personal domain name. DMARC policy is set on a per-domain basis for a sending domain. This means that your domain name would have to be explicitly configured with a DMARC record and that record would have to explicitly configured with a p=reject policy setting. Even if your domain name is hosted by Yahoo, Yahoo isn't changing settings on your domain like this. It would be very unlikely that they would ever do that to everybody's hosted domain names. In short, it's safe to say that it's not really likely to happen to your domain name without your knowledge.
On the "receiving email" side of things, if your ISP respects DMARC policy assertions (that is, rejects mail that fails the DMARC policy specified), you might not receive things like mailing list posts by your fellow mailing list subscribers who use Yahoo Mail. That's the thing that many mailing list managers are working to address.