[exim] Filter/reject own messages by target MX IP

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Autor: Slavko
Data:  
A: exim-users
Assumpte: [exim] Filter/reject own messages by target MX IP
Hi,

recently i start to get medical SPAMs, every message is slighty
different, they use group of different sender domains and different
sender IPs (even from multiple net blocks). Body is simillar, but
about different products. I have no problem to filter them in rspamd,
thus i have no problem with these incoming messages.

What i have problem is DMARC reports for them. All their domains
points to different MX name (with the same pattern, something as
_dc-mx.random_string.domain.tld) which points to the same IP, which
always respond with 421 on connect, i guess that it is intentionally.

I want to reject these (my) DMARC reports, but i cannot add all their
domains into rspamd/exim, as they are changing, thus it will be never
ending work. Instead i want to prevent/reject sending reports which
have to end in that (MX's) IP.

For now i add that IP to ignore_target_hosts in dnslookup router. It
works, but it does more than i want, as for now these SPAMs are
rejected at receive, because sender verification (without callout) fails.
I know, that i can add option to not use that router for verification,
but then verification will fail for all senders, as it is last router for
remote domains. I know that i can disable that verification at all,
but it works fain and i want it.

Please, how i can ensure, that message will be accepted (to rspamd
can learn reputation, bayes, etc from it), but then discard/reject particular
DMARC reports based on target MX's IP? Exists some simple solution,
(which i miss) to create something as dnslookup router which will
reject? Or need i something in ACL (and dnsdb) for that?

regards

--
Slavko
https://www.slavino.sk/