I cannot send mail to ISP nines.nl nor to their customers.
Nines.nl have three MX hosts: two at weight 100, with IPv4 and IPv6 addresses one at weight 500, IPv4 only Their primary MX hosts defer all mail sent to their IPv6 address with "451 Your IPv6 address is not whitelisted at ipv6whitelist.eu". Postfix never tries to connect to the IPv4 addresses of the primary MX hosts, and does not fall back to the IPv4-only MX. Hence the mail stays queued. Somehow I think Postfix is doing the right thing. But I would like some backup before I send a complaint. Thanks, Pim
