The link should take you to the status page where if you click on the circled button it will show you problems UK wide.
You may have to use a "full view" browser if you are on a mobile device.
BT however provide little information Sky who also use Yahoo do provide a bit more detail.
"update 10:28am:- Yahoo are in the middle of recovering their DNS servers. We're still unable to provide an estimated time to resolution.
update 12:43pm:- Yahoo engineers are continuing to work on a DNS issue. Still, no estimated time to resolution supplied.
update 14:22pm:- Yahoo have started to restore services in certain regions around the world."
Farcical. BT should only partner with reliable businesses!
But at least no one has (yet) stated that e-mail is a value-added service, implying that one ought not to rely on it.