It wasn't correcting itself for me. Yahoo blocked quite a bit of messages, and it was happily doing so without any "remorse".

I suspect my trouble started some time after Thanksgiving when many retailers here flooding people's email with advertisements - my inbox average 20 emails every day despite the anti-spam. Apparently the anti-spam bot is screening out the wrong emails!

As koredump suggested, adding the lj_notifications' email address to contact list fixed the problem, hopefully for good!