Well with yahoo domain having a hard fail specified it looks like it's too stay. The typical troublemaker with yahoo mail is lists modifying message bodies or subject lines. Those practices will gauge have to end (and frankly it can't be soon enough imho).
That said the usual consequence is that messages *from* yahoo through the list get binned for Gmail users or anyone else who enforces DKIM. I've noticed Gmail has started marking messages in Spam with the reason why they're there and when they first started a *lot* if them were due to signature fails. There are very few these days which make me believe the lists I'm on have changed practices. Certainly yahoo hasn't rolled back their dns records. So unpredictability makes since sense as the bounces you see will be very dependent on the domains *sending* the messages and their dns records. If you have a thread with a couple yahoo uses talking back and forth you could well see a series of bounces from users on servers that respect Yahoo's dns records requesting a hard fail. -- Greg
