Just to clarify my understanding: On a server with two network interfaces, the first interface has one public IP, the seconds interface has one private (192.168.x.x) IP.
inet_interfaces = all inet_protocols = all #smtp_bind_address = #smtp_bind_address6 = With the following configuration it binds as such tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 21067/master tcp6 0 0 :::25 :::* LISTEN 21067/master The docs say when inet_interfaces specifies no more than one IPv4 address, and that address is a non-loopback address, it is automatically used as the smtp_bind_address Is the second interface with the private IP being considered? With the above config is there a risk of postfix trying to use the 192.168.x.x (or IPv6 equivalent) for outbound connections? Should the bind addresses be specified when using a private network on second interface?