On 04.10.23 16:34, Chris Siebenmann wrote:
>> Now I would like to configure this server as a smarthost, so it will
>> forward emails from my desktop computers (without static IP or DNS).
>> Also, I'd like to have unique mailnames for each desktop, like
>> <hostname>.mydomain.org, to better identify where the mail originated
>> from. But these domains do not really exist, they would be "fake"
>> mailnames to identify the various desktop computers.
> [...]
>> I'm not sure if what I'm trying is possible and sensible. Am I
>> completely on the wrong track here? Are there a better way to
>> achieve something similar?
>
> I think there's a problem with your plan, unless I'm missing something.
>
> If these non-existent unique mail names for your desktop computers
> appear in either the envelope sender address (the SMTP MAIL FROM) or
> the From: header, this is not a good idea by itself because if you
> leak these email addresses out into the outside world, the email will
> either be rejected (for an envelope sender) or unreplyable (for a From:
> header). Here, your existing sender verification is telling you that
> you're trying to send email with addresses that don't work.
>
> To fix this, you'd need to either make the names exist in DNS (even if
> only as MX entries that direct email to mydomain.org's regular mail
> server) or to change your server's Exim configuration so that it
> rewrites all of these email addresses in the envelope sender and the
> address headers. At that point, the only place they'd appear is in the
> Received: header, and if they're only going to appear in the Received:
> header my view is that you might as well not bother.
This is a very interesting and valid point! I could actually quite
easily create MX entries for the host's subdomains on mydomain.org,
so that MX <hostname>.mydomain.org points to mydomain.org.
But does that mean that in turn, each of these subdomains would need
to be added as a local domain in exim on mydomain.org? Are there any
downsides with that? It seems a bit wrong that mydomain.org has local
domains <hostname>.mydomain.org, but that is just my gut feeling, and
I may be wrong here?
All the best,
Mario
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