New Zealands largest ISP uses Yahoo as their email provider and there were reports of this happening as early as February. They've been down playing it but I'm pretty sure that it much more wide spread than they're willing to let on.

http://computerworld.co.nz/news.nsf/news/telecom-denies-resp...

http://www.nbr.co.nz/article/more-problems-telecoms-yahoo-xt...