Spam mail header Analysis

Question

Eu fiz o download do conjunto de dados de spam, pois estou trabalhando na detecção de spam.

Abaixo, um instantâneo do cabeçalho de e-mail recebido.

Received: from localhost (localhost [127.0.0.1])
by phobos.labs.netnoteinc.com (Postfix) with ESMTP id 4BCD643C34
for <jm@localhost>; Wed, 21 Aug 2002 02:45:31 -0400 (EDT)

Received: from phobos [127.0.0.1]
by localhost with IMAP (fetchmail-5.9.0)
for jm@localhost (single-drop); Wed, 21 Aug 2002 07:45:31 +0100 (IST)

Received: from egwn.net (ns2.egwn.net [193.172.5.4]) by
dogma.slashnull.org (8.11.6/8.11.6) with ESMTP id g7L6eVZ13206 for
<[email protected]>; Wed, 21 Aug 2002 07:40:31 +0100

Received: from auth02.nl.egwn.net (localhost [127.0.0.1]) by egwn.net
(8.11.6/8.11.6/EGWN) with ESMTP id g7L6c1J14275; Wed, 21 Aug 2002            
+0200

Received: from athlon.ckloiber.com (rdu25-28-106.nc.rr.com  [24.25.28.106])
by egwn.net (8.11.6/8.11.6/EGWN) with ESMTP id g7L6bcJ13949 for
<[email protected]>; Wed, 21 Aug 2002 08:37:38 +0200

Received: (from ckloiber@localhost) by athlon.ckloiber.com (8.11.6/8.11.6)
id g7L6bYj16433; Wed, 21 Aug 2002 02:37:34 -0400

Alguém poderia explicar por que tantos "Recebidos:" no cabeçalho, e como o e-mail me alcança de acordo com essas informações?