[Lvlug] Mail Handling Recommendations

[Tom Walsh]

> 
> Well, the value of this would be the ability to use IMAP without leaving
> mail on my ISP's server.  On my own server (as you do) I could store 4
> GB (or more) without impacting my ISP.  Then, as you stated, my wife,
> son, and myself (all on the private network) could all access the mail
> on that box via IMAP.  But, the tunneling part scares me (sounds like a
> lot to learn).  Are you sure I'd have to tunnel?

Yup, this would be the only way to do it if you want to keep that box
(that is behaving as your gateway) running MSDOS.  Actually, I seriously
wonder if the MSDOS program is sophisticated enough to do NAT with Port
Redirection.


> 
> Right now we have three computers behind the gateway.  One box, my
> wife's, serves as the main mail machine in the sense that the directory
> that stores the mail on that machine is shared on the network (LAN) so
> Netscape on the other machines can access it.  Any one of the machines
> behind the gateway can surf the Internet and can download email from the
> ISP, without "tunneling" -- IPRoute uses something they call NAT --


Okay, there is a misconception brewing here,  Fetching mail has nothing
to do with you having a mail server, it is only getting mail from
another server.  In order to provide a mail service from a machine on
your own network, you need the co-operation of the ISP and an Internet
Domain of your own (or a static IP from the ISP that they would assign
to you).  Mail servers have names (e.g.  mail.cyberiansoftware.com), you
can have the ISP act as a forwarding agent (lower level preference mail
handler for your domain) and the ISP mail system will spool the mail
until such time as it can contact your mail server to deliver the items
that are being held.



> there are apparently two slightly different things related to networking
> both called NAT.  (Just to finish the story, when any of the other
> machines downloads the mail, it is stored on the shared directory on my
> wife's computer.)  (PS:  I buy very cheap systems, way behind the price
> curve -- most of the machines I have now use TX Pro II motherboards and
> Cyrix, AMD, or Wintek CPUs, ranging from 120 to 300 mhz.)
> 
> Couldn't Qmail, in a box behind the gateway, send / receive IMAP email
> to my ISP over "NAT", just the way my other machines send and receive
> POP3 email through the gateway?
> 
> Oh, wait, <lightbulb turns on> maybe that's the same thing you are
> saying, maybe the thing I call NAT is the same as (or a variety of)
> masquerading?
> 

Under linux we have Network Address Translation provided by the ipchains
firewall. All that NAT does is allow machines that are on a private
network (non-valid Internet IP addresses) have access to the 'net.  NAT
deliberately mangles the port / socket numbers of the packets passing
through NAT so that you cannot run a service thru NAT.  What you need is
a Port Redirector, this is an entirely different animal which is in no
way related to NAT.

TomW


-- 
Tom Walsh - WN3L - Embedded Systems Consultant
'www.openhardware.net', 'www.cyberiansoftware.com'
"Windows? No thanks, I have work to do..."