Mail server for local lan

[Harry Putnam <reader@newsguy.com>]

Setup: Woody/testing  noX 
       Several home machines on a home network
       Behind a hardware firewall (netgear FR314)
       Running exim/procmail

Back in action.. Being the oldest perl student at ucsb was kind of
fun.  Final now over.  Time to play.

I wanted to see a general outline of how one would set up a machine to
handle the mail needs of a local home network.  I have a sort of bare
bones, nox, command line commando machine setup, Running
woody/testing.  It is network ready and has mail setup for its own use
via exim and a smart_host at isp for outgoing but I never set up
retreival as yet since it is experimental and actually receive my mail
on another machine.

I'd like to setup fetchmail to receive all pop3 accounts to the debian
machine. I think I can do that easy enough since I have a fair bit of
experience with fetchmail.

Sort the mail with procmail, again I understand quite a lot of
procmail and have used it for several years.  although not in quite
this context.

The things I'm really unsure about are:

1) What daeman do I need to have running (pop3d Imapd...).  I intend
   to have other household machines retreive via pop3 from this
   server.

2) Do other machine users really have to have accounts on debian box?
   or just a mailbox at /var/mail?

3) If I have a daemon running, is it possible to setup so that it only
   runs when a machine connects.

4) How can I bar any machines that are not 192.xxx.xxx from the
   143/110 port.

5) what do I have to tell exim in order for it to know to send the
   other machines outgoing mail to my isp smart_host.

6) can all this be made invisible to the internet, so that a scan will
   not show 143/110 as running or open?

I am behind a hardware firewall already (Netgear FR314) which I think
will hide the open ports from the internet. but still want
to make all precautions.  And know how to setup so that only my network
machines get access.