You may recall that Yahoo initially implemented a "p=reject" DMARC policy back in April, 2014 for their primary yahoo.com domain name. (And AOL did the same for aol.com shortly after.) This changed the email landscape significantly. Now, nearly two years later, the email landscape is a different one. Email discussion lists needed updating to keep up, but even with limitations inherent, many of us consider DMARC to be a successful tool in the spam and/or fraud fighting arsenal.
Yahoo implemented a "p=reject" DMARC policy for their ymail.com and rocketmail.com domains in November, 2015.
Today, Yahoo announced on the DMARC-Discuss mailing list that they are implementing a p=reject DMARC policy for forty-six different Yahoo international domains on March 28, 2016.
Update: On Monday, March 7th, Yahoo updated the list, adding sixteen additional domains. The full list is below.