This would not exactly enhance goodguy's reputation,
or Yahoo's for that matter. I realise it isn't the exploit
that Yahoo is trying to stop, but it suggests to me that
DMARC is only plugging one small hole in a very leaky dam.
No kidding. DMARC is only useful because most spammers and phishers are
remarkably stupid. But not all of them.
R's,
John