Pim Zandbergen:
> 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.
I know of no RFC that says only whitelisted clients can send email
over IPv6.
There are two solutions for these idiots:
1 - With Postfix >= 2.8, specify "smtp_address_preference = any".
This randomizes the order of IPv4 and IPv6 addresses with the
same MX preference, so that all mail will eventually go through
(as long as they specify at least one IPv4 address for at least
one primary MX host).
The historical default, inherited from the IPv6 patch, was to
randomly try IPv6 addresses with MX preference "X" before
randomly trying IPv4 addresses with the same MX preference "X".
2 - Increase smtp_mx_session_limit (default: 2) so that Postfix
will knock more doors.
This limit, and smtp_mx_address_limit (default: 5) exist to
protect Postfix against idiot spammers that set up a ton of MX
records with non-responding servers.
Wietse
