Most times I simply delete the mail as well, but sometimes I use the IP-number of the original sender and forward the received junk-mail untouched to firstname.lastname@example.org, whereas provider stand for the owner of the IP-number which is normally a provider. Most spammers don't have an IP-number of their own but use a number which is free at the moment they log in.
In my case the header looked like this (I censored some parts to protect my email adress as well as the privacy of an unknown person - the fake-sender):
Return-path: *fake email of sender*
Envelope-to: *my real email*
Delivery-date: Mon, 21 Jul 2003 12:47:14 +0200
Received: from [188.8.131.52] (helo=184.108.40.206)
by mail01.ims-firmen.de with smtp (Exim 4.12)
for *my real email*; Mon, 21 Jul 2003 12:46:45 +0200
Received: from 6i.vzecpyr.org (HELO mwu7q) ([220.127.116.11]) by 18.104.22.168 with SMTP; Mon, 21 Jul 2003 10:38:17 -0100
From: "*fake name of sender*" *fake email of sender*
To: *my email again*
Subject: Guaranteed 12%-50% Discount On All Prescription ... bm y iskzso l oxe
* ... more blahblah ...*
The first "received from" is my, or my provider's mail-server. The second is in this case the last - read: the first server that sent the mail.
As you can see, from 6i.vzecpyr.org (HELO mwu7q)
are most likely randomly written entries, but the IP-Adress in brackets  is real. The website I have linked to returns the provider to whom you can report the abuse.
Mor about mail headers here: http://www.stopspam.org/email/headers/headers.html
I thought of that, too but it's equally unlikely a mail-server of the DoD has an open relay and somebody from the outside world knows of it, can make use of it and get away with it.
[Edited 2003-07-21 18:16:48]