Qmail vpopmail noip.com confusion. Please help.

[OhSh33t]

I'm totally confused and can't get a straight answer from anyone on this and am finding nothing as I read through zillions of post's regarding qmail and vpopmail. Basically I'm confused about my outside public domainname and my internal domainname that I use on my fake RFC1918 network and what I need to tell qmail/vpopmail in regards to which one???

Public, Private or both?? The Gentoo Qmail/Vpopmail Guide doesn't touch on this point at all. Do I give qmail my fake internal domainname and vpopmail my pubilc domain name??

I'm setting up qmail for family and close friends to have email accounts on this server. I don't want them to have local system accounts to send and retrieve mail, and that's what I thought "vpopmail" would help eleavate.

But my outside public domainname is "mydomain.com" and my internal domainname is a fake "deadmeat.com" domain on private ips separated by a firewall doing masq'ing and portforwarding.

I have a dyndns account and registered public domainname through noip.com. They also manage all dns records for my domain. All my dns records are setup correctly. Not worried about that. But what do I tell qmail and vpopmail in regards to the what the domain is?

My network layout is:

Internet
|
Cable-Modem
|
Eth-0 (dhcpcd dyndns client ip address)
|
"Gentoo, 2-interface Server running Shorewall firewall. Port forwarding as needed"
|
Eth-1 (Static 192.168.254.1/24)
|
Internal domain "deadmeat.com". Gentoo Server running Apache and Qmail/vpopmail

When I follow the Gentoo Qmail/Vpopmail doc it has me listing my internal fake domain. This is the part that is confusing me. Obviously when someone sends email to "newaccount@mypublicdomainname.com" that eventually gets relayed to my external ip which is port forwarded to my internal Gentoo server running Qmail. But by following the Gentoo Qmail/Vpopmail doc, qmail is going to have all my fake internal domain info. Can someone tell me how this is supposed to be setup? I'm sure I'm missing something totally small as usual.

Or do I need to switch my internal domainname to what I have registered on the public internet?

Thanks
_________________
JB