A-ha - went to their forum and found this:
Ade Jan 07
I just wanted to let everybody know that we've temporarily disabled email notifications for new questions. It's something we're trying to bring back soon, but the volume of emails are so high that:
they're the major cause of delays for questions appearing in inboxes
they're causing many of the deliverability issues for more critical emails, such as password resets
they're peripherally affecting other pieces of the infrastructure
Sorry about the trouble. It unfortunately won't be a quick fix, but I'll update this thread when there's more info.