I didn’t update yet, I guess the ipv6 chain is different now due to the changes
EDIT: I updated my mailcow testsystem, I still have the chain “MAILCOW” in my ip6tables output
testcow:/opt/mailcow-dockerized# ip6tables -L | grep Chain
Chain INPUT (policy ACCEPT)
Chain FORWARD (policy DROP)
Chain OUTPUT (policy ACCEPT)
Chain DOCKER (1 references)
Chain DOCKER-BRIDGE (1 references)
Chain DOCKER-CT (1 references)
Chain DOCKER-FORWARD (1 references)
Chain DOCKER-ISOLATION-STAGE-1 (1 references)
Chain DOCKER-ISOLATION-STAGE-2 (1 references)
Chain DOCKER-USER (1 references)
Chain MAILCOW (1 references)
Just ran the script there, works as intended. Maybe don’t run it with sudo but directly as root user