Have noted that as of just before lunch today, xtra.co.nz is being deferred from SMTP delivery. By extension anyone with domains hosted @ xtra is also going to be affected.

It also seems that mail exiting Xtra is being held up. I gather theyve had a big spam bomb hit them or some such. But if you're affected, well, now you know - more informative than http://xtra.co.nz/help is being...
As it currently stands it reads 'There are no known problems with the Xtra Network'... (as usual).