DKIM smarthost transport

[Andreas Metzler]

On 2023-06-08 Tom Wijnroks <t.wijnroks at exonet.nl> wrote:
> Hello,

> I'm running Exim4 (split config) and use local macros from Debian/Exim4 to setup DKIM signing:
[...]
> It works fine when relaying directly to the internet but it does not when relaying through a smarthost. This is because the DKIM macros are not present in the smarthost transport:
[...]
> Is there a reason why it was left out from the smarthost transport?

Mainly that a DKIM signature of a smarthost using host are usually not
very useful. They usually do not have DNS record to check the sig
against and the main point of DKIM nowadays (to increase trust and the
lower the chance of being falsely flagged as spam-server bei gmail and
others) is not relevant.

For reasons given above we probably would want to have separate knobs
for enabling DKIM signing on the smarthost transport which would again
complicate an already byzantine configuration.

cu Andreas

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