Re: [exim] SMTP transport interface IPv4/IPv6

On 06/09/2022 12:37, Kai Bojens via Exim-users wrote:
> Am 06.09.22 um 12:53 schrieb Jeremy Harris via Exim-users:
>
>> The "interface" option says "use the interface that has this IP.
>> It does not say "use this IP".
>
> Ah, I see – I didn't know that. Thanks.
>
> But, then again there is an explicit virtual interface with that IP on my server Host A:
>
> ens3: IPv4 & IPv6
> ens3:400: IPv4
> ens3:401: IPv4
> ens3:402: 1.2.3.4 (IPv4 only)
> ens3:403: IPv4
>
> (and so son)
>
> I would have that thought that exim then chooses ens3:402 for outgoing mail,

You're into the detail of how the kernel behaves when describing
interfaces to applications, here. I can quite imagine that the
detail of "virtual" interfaces gets lost - and it's bound to be different
on different platforms too.

> but it decides to use ens3 and IPv6. Is there any way to change this behaviour?

If you want to use specifically IPv4 for this connection (but why?)
then the message has to be labelled with only IPv4 addresses.
The labelling will be being done by (most to least likely)
- a dnslookup router
- a manualroute router
- the smtp transport "hosts" option
--
Cheers,
Jeremy