Dear, in order to fine tune some antispam configuration on an our smarthost relay (proxmox mail gateway) I'd like to add a custom header to the mail the are sent via forward from ispconfig. Anyone here can point me out on the right direction in order to add a custom header on the mail, if the mail pass through the mail_forwards table? I'm trying to write my own milter in order to do that, but i'm not sure that this is the best/easiest and most common way... ty
tl;dr; This is necessary because a large portion of the spam we forward originates from incoming emails that are simply forwarded externally using our IPs. As a result, we want to apply more aggressive spam filtering specifically to forwarded emails, in order to protect our IP reputation. ty(2)
probably the best way (hope so) is the rspamd milter functionality. checking if the Delivered-To and To field are different and if yes, add my custom header. In that way i must not rewrite a different milter and use only something (rspamd) that i'm already using. The only things is that i'm not super secure that checking if Delivered-To header against To header is solid enough
