How to prevent, or change priority, of dovecot's FAILed relay-submission to relay's IPv6 address, and submit ONLY/first to IPv4?

[@lbutlr]

On 09 Apr 2021, at 07:57, Arjen de Korte <build+dovecot at de-korte.org> wrote:
> Citeren PGNet Dev <pgnet.dev at gmail.com>:
>> And it's a bad assumption that since the host is dual-stack that all services on it will be.
> I fail to see why. If a hostname resolves to both an A and AAAA record, it should provides services on both.

Yes, that would be my stance on it.

>> The 'solution' is to have Dovecot relay submit connect where & how you TELL it to connect, NOT where it assumes it's OK to connect.
> 
> You've already told it where to connect: internal.mx.example.com. Since that host has both an A and AAAA record, you're telling it both are equally fine. If that's not what you want, either hardcode the IPv4 address in the submission_relay_host or create an internal-ipv4.mx.example.com A record.

Right. The tools are already there, there is no need for dovecot to add another specific setting for this edge case when it is entirely unnecessary.

> It's a head scratcher why people still insist on running services on legacy IPv4 only.

Some of us have no choice, sadly. Two of the largest ISPs (Comcast and Century Link) in the US refuse to offer IPv6 to business customers, and have gone to some lengths to screw up IPv6 for their consumer customers.

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