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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