Doing blacklisting of IPv6 addresses is actually quite hard, because you can't know how network owners lay out their addresses. Some networks (especially VPS pr

Doing blacklisting of IPv6 addresses is actually quite hard, because you can't know how network owners lay out their addresses. Some networks (especially VPS providers) will use one /64 (or so) per datacenter, while other will give out a /64 for individual users. So when 2001:db8:a1:b2::c:3 has sent spam to you, you can't know if you should block the network 2001:db8:a1:b2::/64 or the specific address 2001:db8:a1:b2::c:3. Some blacklists (carelessly) take the former approach and block entire datacenters.