Mail delivery question

[Hal Finney]

I have a somewhat dumb question about mail delivery.  This has a CP
connection because it relates to a remailer enhancement I am working
on.  When I receive mail from cypherpunks, this is a typical set of headers
for an incoming message:

  From owner-cypherpunks at toad.com  Wed Oct 20 23:57:11 1993
  Received: from nova.unix.portal.com by jobe.shell.portal.com (4.1/1.34)
  	id AA14713; Wed, 20 Oct 93 23:57:11 PDT
  Received: by nova.unix.portal.com (5.65b/4.1 1.505) 
  	id AA18779; Wed, 20 Oct 93 23:57:09 -0700
  Received: by toad.com id AA20355; Wed, 20 Oct 93 23:47:55 PDT
  Received: by toad.com id AA20115; Wed, 20 Oct 93 23:43:21 PDT
  Return-Path: <jamie at netcom.com>
  Received: from netcom.netcom.com ([192.100.81.100]) by toad.com id AA20111; Wed, 20 Oct 93 23:43:19 PDT
  Received: from netcom3.netcom.com by netcom.netcom.com (5.65/SMI-4.1/Netcom)
  	id AA27104; Wed, 20 Oct 93 23:43:51 -0700
  Date: Wed, 20 Oct 93 23:43:51 -0700
  Message-Id: <9310210643.AA27104 at netcom.netcom.com>
  X-Mailer: Eudora
  To: cypherpunks at toad.com
  From: jamie at netcom.com (Jamie Dinkelacker)
  Subject: Re: Something Silly, Something Serious
  Status: RO

Now, my question is, when this mail is delivered to the Unix system which
I use, how does the local software know to deliver it to hfinney?  My name
does not seem to appear in the header at all.  In particular, the "To:"
address is not hfinney at shell.portal.com, as I would have expected, but rather
cypherpunks at toad.com.

I suppose there is some other information that is passed along with the
message when it is delivered to portal.com, information which tells my
user name.  It would be nice if this information were available to scripts
which would process the incoming mail.  Could someone explain how this
delivery process works?  Thanks -

Hal Finney
hfinney at shell.portal.com