I have setup proxmox mail gateway in front of exim with many domains. But only some domains in exim are enabled for mail gateway. But sometimes, those domains recieve spam mails bypassing mail gateway. Because spammers are directly deliverying mails to exim ip.
So I need to set a rule in exim-filter (I think), to accept mails from only mailgateway hostname and reject the rest. But must be able to be done per domain basis.
Can you guide me?