This mailinglist is not really a means of contacting the netfilter/iptables project, but rather a way of the iptables people contacting and informing their users about new releases, bugfixes, potential security issues.
This mailinglist is recommended for netfilter/iptables users who have questions on the usage, setup or configuration of netfilter/iptables, or of course those who want to help other users by sharing their experience and knowledge.
This mailinglist is used for discussion among netfilter/iptables developers.