I just did [a test][1] 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]/128 192.168.1.0/24inet_interfaces = 192.168.1.1, 127.0.0.1where 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?
Port 110 visible to the outside world - necessary or a bad idea?
security;postfix
Having port 110 (POP3) open and available is completely normal if your intention is to run a POP server. POP3 is perhaps a bit archaic/obsolete and you might consider using IMAP instead, but there is nothing fundamentally wrong with it.I don't know what test you used, but it might be that it is signalled as a problem because STARTTLS is not supported, which means passwords will be sent in the clear. The POP3 protocol supports STARTTLS but it seems like popa3d might not. Perhaps you should consider using a better POP server, such as Dovecot. Dovecot also supports specifying which IP addresses to listen on in its config file, which popa3d also appears not to support, so perhaps you might also want to use that if you want to accept POP3 connections only on the WAN and not on the LAN.By the way, you listed Postfix configuration directives in your question, which have nothing to do with POP (or IMAP).