CircleID

Primary source information on this matter can be found at the Australian Communications and Media Authority's website: ACMA registers internet industry code on spam.

From a technical perspective, this code of practice is noteworthy in that it considers publication of SPF records a "best practice" to be followed. It also prohibits open proxies and open relays, whether on the ISP's hosts or customer hosts, and reserves the right for ISPs to scan for such services as a part of enforcing their AUP. Outgoing mail must use SMTP "AUTH" or similar, and outgoing port 25 blockage is required of dynamically addressed hosts "where technically and commercially viable".

The "best practice" SPF requirement is a little dubious, given that development in this area (MARID — Mail Authentication Records In DNS) is still very much a work in progress. Still, that particular requirement has very little impact in actual practice, since it's quite possible to publish an explicitly noncommittal SPF record.