I just did [a test] that told me my gateway's (debian squeeze) port 110 is visible from outside.
It's a box with two network cards, eth0 is for my internal network (192.168.1.0/24) and eth1 goes to "the internet" (as ppp0).
Is an open port 110 on the outside connection a necessity when I run postfix, use the box to collect mail using fetchmail, and have the mail collected by internal boxes using pop3 (popa3d)?
Is everything o.k. as long as my postfix has a main.cf with lines like these?
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 192.168.1.0/24 inet_interfaces = 192.168.1.1, 127.0.0.1
where 192.168.1.0/24 is my home network and 192.168.1.1 is eth0?
Or was I stupid and opened a port I should rather have closed or invisible to the outside network?