Re: [exim] OT: DKIM - but nothing to do with Exim!

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Author: Luca Bertoncello
Date:  
To: exim-users
CC: exim.ml
Subject: Re: [exim] OT: DKIM - but nothing to do with Exim!
Ron White <exim.ml@???> schrieb:

> Now, another domain comes on stream with this shared MTA - say
> 'anotherdomain.null'. How can this ever send mail that is DKIM signed
> when the private key is for somehosting.null?
>
> Obviously I'm missing something really obvious here in my understanding.
> Can anyone put me out of my misery?


Hi, Ron!

I can't say you how to do that with other MTAs as Exim, but with Exim is
really simple!
This is my configuration (just the part used to send out E-Mails):

Router:

external_gw:
  driver = dnslookup
  transport = ${if exists {/etc/exim/domainKeys/$sender_address_domain}
                     {remote_smtp_DK} {remote_smtp}}
  domains = !+local_domains
  no_more


Transport:
# Transport for sender domains WITHOUT DomainKeys
remote_smtp:
driver = smtp

# Transport for sender domains WITH DomainKeys
remote_smtp_DK:
driver = smtp
dkim_canon = relaxed
dkim_domain = $sender_address_domain
dkim_selector = ${substr{0}{4}{$tod_zulu}}
dkim_private_key = /etc/exim/domainKeys/$dkim_domain/$dkim_selector.priv

Now, in /etc/exim/domainKeys I have many directories, with the name of the
domain on my server that use DKIM to sign outgoing E-Mails (for example
lucabert.de, lucabert.com and so on).
Et voila! The E-Mail from something@??? will be signed with the DKIM
for lucabert.de, the E-Mail from someotherthing@??? (other domain on
my server) will be signed with the DKIM for lucabert.com.

Really simple, isn't it? :)

Regards
Luca Bertoncello
(lucabert@???)