IPV6 for Mail-in-a-Box

Probably, but I have been on the list for a while now, no impact.

If you are determined it’s due to UCEProtect, then you either wait it out, or change your IP. IPv6 only is not recommended as stated above.

Mailinabox, if i’m not wrong is configured to run on both. If you want only IPv6, then disable your IPv4.

Other than that there’s nothing you can do on your end.