* Auke Kok:
So, for postfix, there is no default config as this properly
anyone from accidentally becoming an open relay.
I'm aware that Postfix configuration can be a complex issue. Part of my
business is centered around all things email. What I find very useful
while setting up a new Postfix instance are the following options:
# (1) Listen only on loopback interfaces, i.e. 127.0.0.1 and ::1
inet_interfaces = loopback-only
# (2) Only this machine is considered a "trusted network"
mynetworks_style = host
With setting #1 in place, there is no way for external clients to
connect to Postfix. I also keep #2 around for permit_mynetworks until
I have verified that all relay restrictions are working as expected.