yahoo domainkeys and antispam are broken
Since a few weeks we get more and more spam that passes the antispam filters from Yahoo, but recently even mails (phishing) that claims to come from Yahoo has passed their filters and even their domainkeys should normally have stopped this mail because normally Yahoo would have seen that this mail couldn't come from Yahoo and should have blocked it.
There is nothing worse than telling people that you have built a system that will identify if a mail comes from a certain mailserver so that people will trust mail that says it comes from your services (but not from your mailserver) and letting it degrade.
I can understand that Yahoo is going through rough times and maybe people got fired, replaced or aren't doing their job properly any more, but the biggest advantage of Yahoo the last years was that it was one of the best antispam and antiphishing services around.
This is changing and fast. Maybe it is because Trend Micro is also degrading fast - which is the reason people are throwing Trend Micro solutions out of the window and choosing other solutions. But there is definitively a problem with domain keys here
Or before there was a lonesome soldier having a human watch on the traffic and adapting strategies to the tactics of the spammers.
These are the headers of the mail - and this is the reason you should always look at the headers if you aren't sure (or at the source of the page - rightclick)