Anyone else having SMTP issues tonight?

I have a blueyonder email address and my email client uses pop3/smtp protocols. I've been sending and receiving emails all day today, up until an hour ago, since when I'm getting Authentication error messages and nothing will send. I've not changed any of my account settings today, so it can't be that.  I checked to see whether there are any known issues systemwide or locally (Bristol NW, BS6) and there's nothing reported so far.  What gives?