Terry Zink published a 5-part article on IPv6 Email on MSDN in 2012. Part 2 was
Why we use IP blocklists in IPv4, and why we can’t in IPv6.
Quote:
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Originally Posted by Terry Zink
...To put it one way, there are 250 billion spam messages sent per day. Under IPv6, spammers could send out 1 piece of spam per IPv6 address, discard it and then move on to the next IPv6 address for the next 10,000 years and never need to re-use a previous IPv6 address....
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The TL;DR of the series is that only whitelisting will be effective, rather than blocklist/blacklists.
Zink foresees manual greylisting (website form-filling with captcha) to consider new whitelist memberships, which I believe would be unworkable at any sort of scale, and is only possible if those seeking whitelisting use static addresses. If autoconfiguration privacy extensions are deployed, even whitelisting is a non-starter unless one whitelists the 64/ subnet.