Interesting with netstat there is no nsd with ipv6:
netstat -tlnp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:10023 0.0.0.0:* LISTEN 15680/postgrey --pi
tcp 0 0 0.0.0.0:4200 0.0.0.0:* LISTEN 24461/shellinaboxd
tcp 0 0 127.0.0.1:10025 0.0.0.0:* LISTEN 12579/perl
tcp 0 0 127.0.0.1:10026 0.0.0.0:* LISTEN 23957/dovecot
tcp 0 0 0.0.0.0:587 0.0.0.0:* LISTEN 24146/master
tcp 0 0 127.0.0.1:10222 0.0.0.0:* LISTEN 8175/python
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 19483/nginx: worker
tcp 0 0 0.0.0.0:10000 0.0.0.0:* LISTEN 453/perl
tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 12310/named
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 448/sshd
tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 24146/master
tcp 0 0 127.0.0.1:953 0.0.0.0:* LISTEN 12310/named
tcp 0 0 127.0.0.1:8891 0.0.0.0:* LISTEN 13616/opendkim
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN 19483/nginx: worker
tcp 0 0 127.0.0.1:8893 0.0.0.0:* LISTEN 21029/opendmarc
tcp 0 0 0.0.0.0:4190 0.0.0.0:* LISTEN 23957/dovecot
tcp 0 0 0.0.0.0:993 0.0.0.0:* LISTEN 1/init
tcp 0 0 0.0.0.0:995 0.0.0.0:* LISTEN 23957/dovecot
tcp6 0 0 :::587 :::* LISTEN 24146/master
tcp6 0 0 :::80 :::* LISTEN 19483/nginx: worker
tcp6 0 0 :::4949 :::* LISTEN 12729/perl
tcp6 0 0 :::22 :::* LISTEN 448/sshd
tcp6 0 0 :::25 :::* LISTEN 24146/master
tcp6 0 0 :::443 :::* LISTEN 19483/nginx: worker
tcp6 0 0 :::4190 :::* LISTEN 23957/dovecot
tcp6 0 0 :::993 :::* LISTEN 1/init
tcp6 0 0 :::995 :::* LISTEN 23957/dovecot
best regards