[PLUG] originating IP address

[David Hull <dave@microphotonics.com>]

Ok... I'm trying to understand how this works.  I had a problem where
the originating IP address inside my mail headers was incorrect (i.e.
not the address of my mail server, but rather that of my router).  The
headers looked like this:

Received: from postman5.mx.aol.com (postman5.mx.aol.com
[205.188.157.132])
        by mailops.mail.aol.com (8.9.3/8.9.3) with ESMTP id PAA05121
        for <angarita@mailops.mail.aol.com>; Tue, 26 Mar 2002 15:31:28
-0500 (EST)
Received: from 12.34.567.89 (host-12-34-567-89.choiceone.net
[12.34.567.89])
        by postman5.mx.aol.com (8.11.1/8.11.1) with ESMTP id
g2QKV7x16508
        for <angarita@aol.net>; Tue, 26 Mar 2002 15:31:07 -0500 (EST)
Received: from microphotonics.com (host-12-34-567-89.choiceone.net
[12.34.567.89])
        (authenticated)
        by 64.65.217.10 (8.11.6/8.11.6) with ESMTP id g2QKUXv17133
        for <angarita@aol.net>; Tue, 26 Mar 2002 15:30:34 -0500

I managed to get them to look like this by changing an entry in my
/etc/hosts file (I had forgotten to change it when I switched things
around):

Received: from mail.microphotonics.com (host-12-34-567-89.choiceone.net
[12.34.567.89]) by rain.CC.Lehigh.EDU
              (8.12.2/8.12.2) with ESMTP id g2QKgAxs019997 for
<dmh2@lehigh.edu>; Tue, 26 Mar 2002 15:42:10 -0500
Received: from microphotonics.com (host-12-34-567-89.choiceone.net
[12.34.567.89]) (authenticated) by mail.microphotonics.com
             (8.11.6/8.11.6) with ESMTP id g2QKfHT17309 for
<dmh2@lehigh.edu>; Tue, 26 Mar 2002 15:41:17 -0500
             Message-ID:  <3CA0DCFD.47824AA0@microphotonics.com>

However, the originating IP address was still wrong.  After trying the
MASQUERADE_AS, with masquerade_envelope to no avail, I finally went into
my router and started playing around with stuff there.  I had been using
NAT to get the router to connect the server's public IP address with
it's private one.  It's a Netopia router and the way to do this is to
specify the port you're allowing (so 25 for smtp, 143 and 993 for imap,
etc.) and then provide a public/private IP pairing.  I nixed this, and
looked up how to do static address mapping.  Once I had this setup, I
finally got the headers that I wanted.


Received: from mail.microphotonics.com (mail.microphotonics.com
[789.456.123.123]) by rain.CC.Lehigh.EDU (8.12.2/8.12.2) with
               ESMTP id g2RKDvxs002913 for <dmh2@lehigh.edu>; Wed, 27
Mar 2002 15:13:57 -0500

Received: from microphotonics.com (host-12-34-567-89.choiceone.net
[12.34.567.89]) (authenticated) by mail.microphotonics.com
                (8.11.6/8.11.6) with ESMTP id g2RKD4v22213 for
<dmh2@lehigh.edu>; Wed, 27 Mar 2002 15:13:04 -0500

My question is this... why did the static address mapping all of a
sudden make this work.  How does the sendmail program find out what IP
it is sending a message from, and why didn't it find the correct one in
the first place?


-dave


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