Multi-homed box acting as a DNS and Mail Server.

[Melvin Toy]

Hi-

I'm a newbie experimenting with bind and sundial.  I have a box at home
with 2 nics(one real static IP and other private 172.16.x.x) running
Redhat 6.1 with a cable modem.  I have another box (box A) running RH6.1
at home with a private IP and one (box B) at work running solaris 2.7
with a real IP. I temporary add my DNS server as the name server for box
B. I can email from my dns/mail server and it also relays box A messages
to box B and masquerades correctly.  However when I reply, my mail
bounces.  I tried to telnet to port 25 by FQDN of the dns/mail server
from box b.  I notice it was trying to telnet to the private IP instead
of the real one.  When I do an nslookup by name both IPs are return.
How do I get box B to use the real IP every time.  I know I going to
have more issues with sendmail but I'm trying to eliminate all
non-sendmail problems first. My first thought is to create a separate
record for the internal nic. Is that legitimate and typical solution?
How will that will affect sendmail?

Thank you
Melvin