Re: [exim] SMTP transport interface IPv4/IPv6

On 2022-09-06 Kai Bojens via Exim-users <exim-users@???> wrote:
> I have a question about the "interface" option and which IP protocol it
> chooses as I obviously don't understand it fully.

[...]
> Host A: Has a transport with an explicit "interface = 1.2.3.4" IPv4

> Host A now sends mail to Host B and uses this transport correctly but
> chooses the hosts's IPv6 instead of the configured interface IPv4 address.

"interface" does not set the protocol (IPv4/IPv6).

Quoting spec:
| The first interface of the correct type (IPv4 or IPv6) is used for the
| outgoing connection. If none of them are the correct type, the option is
| ignored. If interface is not set, or is ignored, the system’s IP
| functions choose which interface to use if the host has more than one.

Afaiu the router determines the destination (IPv6 or IPv4 host) and the
transport can only go from there.

cu Andreas
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