I wrote a small piece of code today, addressing the problem that DNS Blocklists are not working for Mailservers in a NAT64 enviromnent.
$ host -t A 9.0.a.d.a.e.b.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.b.9.f.f.22.214.171.124.dnsbl.fnordpol.de 127.0.0.1
Using domain server:
9.0.a.d.a.e.b.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.b.9.f.f.126.96.36.199.dnsbl.fnordpol.de has address 127.0.0.2
this is currently working on my development laptop. It is a small python script which thinks that all it gets is a NAT64 prefixed IPv4 so it builds an ipv4 query out of the V6 address and forwards that thing to the real blocklist provider.
It surely needs some refinement, to make it operative.