Just received the following from the Yahoo! Postmaster team.
"We're seeing intermittent connectivity issues across our yahoo.com MXes starting early this morning.
If you are suddenly seeing queues to Yahoo! Mail, please stay tuned for updates and please refrain (at least for now) from contacting our Postmaster team about any deferral issues you started experiencing today. We're doing our best to get this resolved ASAP."
I will update again once I receive an update.