We have a conflict with spamhause abou one of us network. And till this hapend we wish forward all 25 ports from one subnetwork to other one. in example:
193.x.x.x is in SBL now, need without IP changing at customers forward all mails to 195.x.x.x IP.
Also question: in that solution will be need some smtp relay server what will be work as proxy for accepting mail from inside subnetworks?
Add destination NAT rules for SMTP to the gateway routers of all networks. The below forwards all SMTP traffic to a host with IP 1.1.1.1. Yes, that host will have to be an open gateway. Also, that host is going to have to be configured to accept mail from all usernames and passwords anyone may have configured for their SMTP server. That’s the trickiest part.
/ip firewall nat
add chain=dstnat protocol=tcp dst-port=25 action=dst-nat to-address=1.1.1.1