One of my mailhosts recently added IPv6 addresses to their servers. Since then, I have been unable to add the new addresses as valid mailhosts. The configuration process appears to be successful:
...but the reporting fails to identify the new server address as "safe." Here is an example (email address and unique Spamcop identifier redacted):
Also, the IPv6 address isn't listed when I review my known mailhosts.
I did try to solve the issue by deleting and re-adding the mailhost. I suspect the issue is that the servers are operating in both IPv4 and IPv6 namespace.