I have been using mail-in-a-box on two VPS for several months now. Love it, thanks for providing.
One box stopped running due to DNS at registrar (I think). Updated to v0.18c, had same DNS nameserver related errors. After moving to Gandi and setting nameservers and glue records, mostly green but still was getting red “Public DNS (nsd4) is not running (port 53)”. Ran script again, no change. Tried to start nsd / reboot several times but nsd would not run. Then compared /etc/nsd/nsd.conf with other box I use and noticed the IPV6 address was missing. I added it (even though warning says not to modify /etc/nsd/nsd.conf). Rebooted, and now working fine.
I have not updated my other box from v0.18b to v0.18c yet but will see if that had anything to do with missing/deleted IPV6 and report.