I have tried sending this to the proper channels and have been ignored.

mail.asiaonline.net.nz's spam filter instead of rejecting emails it doesn't like defers them which mean they sit in our mail queue for a week retrying every 4 hours and clogging our and their mailservers.

This seems to me like a rather nonsensical thing to do.

Almost as nonsensical as spammers or mail servers that originate mail, are the listed MX for the domain and yet refuse to accept bounce messages (4xx defered messages of course.. or even better "what ? you actually expect me to be running a mail server ??" ) and hence clog up the ISP's mail queue... Not saying that this is always the case, yet its always a great way to come to the attention of the postmaster when they are busy updating their spam filters Defering mail also allows the postmaster at the originating domain time to contact said ISP and request the blocks be removed and then allow mail to flow a-beit with a delay. It also may raise the issue to the level where the postmaster of the originating box actually notices and does something to fix the problems that caused them to be listed in the first place.. Have you tried ringing ICONZ and asking to talk to someone there that looks after the mail system ? generally that is kinda hard to ignore and they may be able to tell you the original issue that got the domain listed so that you can fix it before they open their system back up again. -- Steve.