[nznog] Greylisting New Zealand whitelist

Hi there, Is there a list of NZ networks or mail hosts that are considered OK for whitelisting in an email greylisting implementation? I realise that there are trust issues etc etc but what I want to do is have domestic mail from known providers (ie ISPs and hosting providers) essentially unhindered by the usual time delay of greylisting. We're using qmail, and the greylisting options are a bit basic. If there isn't a list would I be correct in assuming that moving to postfix and using postgrey with its database learning / remembering option would be a smart move? I realise that this is verging on off topic, but my googling has netted ziltch. Regards, Gerard