Re: [exim] local_domains by dns

Am 26.08.21 um 15:35 schrieb Jan Ingvoldstad via Exim-users:
>
> But if a domain holder changes the domain's DNS records to indicate that
> delivery should happen at a different MX, it is not, ordinarily, reasonable
> for a provider to override that.
>
>

Thanks to any suggestions made, they were very helpful.

I found a way:

- New Router ( top position in router chain )
- for local_domains check if they have external mx
- check if mail comes from 127.0.0.1 OR has SMTP-AUTH
(- add checks for your relayhost configs )
- send to external mx, instead of processing locally.

... continue with normal routine ...

This covers all the requirements[we had]:

local keeps being local,
external mx get mails,
and external processors of any kind can send in mail after processing.
It does not generate loops.
(and if spammers try this host, antispam setup kicks in)

and it's already confirmed working. I could say, it came to me in a
dream, but it was more one of those heureka moments, while writing a
mail, why it doesn't work :D

Unfortunately, this router needs some help from outside exim to
function, as exim can't do the necessary mx checks, as it's logic is too
complicated and not implemented. You can use perl for it(live), or build
a domainlist of any kind(periodic checks).

if anyone thinks, this routersetup has a loophole, feel free to discuss
it, anyone will profit from it.

best regards,
Marius