(Solved) Subdomain mx / sending (DMARC)

Dear Community,

I want to run on a subdomain my own mailman installation. I have successfully build everything up and it runs smoothly. But the DMARC settings nack me - if the recipient takes care of such settings the mail will be blocked.

My question now - how can I run a Mail system on the external System for a Subdomain?

box.example.org holds example.org. The Subdomain mailman.example.org points to a different host, having A, AAA and MX records set up in the custom DNS Settings.

Receiving emails is possible, but because the subdomain is not excluded from DMARC and/or mailman.example.org is a valid sender the mailman server can’t reach all recipients.

How can I configure either the DMARC settings to make mailman.example.org valid or make it possible to relay all messages via the MIAB. With the second option - creating one account/alias for the subdomain on the box MIAB will overwrite the MX Records added adds itself with the priority of 10. What makes the MIAB a Backup/secondary MX for that Domain what is not wanted (as I would need to configure fetchmail for that box to get even the mis-redirected messages to the lists.

// Edit 1

When I try to override the DMARC Settings the result is something inconsistent. Because the Domain holds two DMARC Records now …

I’ll resolve this myself.

After I had identified how I’m able to overwrite some settings I was able to make a subdomain using a dedicated mail system.

grafik

I needed first the A/AAAA Records for the host, followed by the MX host followed by overwriting the SPF Record that is created by MIAB followed by overwriting the DMARC Record from MIAB.

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