What have you done about it? The old webmail interface doesn't exist now so you have to use the Yahoo/Xtra one.
Did you sign up? Telecom claim to have fixed the problems with the registration system. I only got part way through it but that seemed enough to be able to logon to webmail.
There are new Outlook settings for your account http://xtra.co.nz/help/0,,4150-4453061,00.html