Need help with headers

Hi,

First let me say that I did read - I went out and I bought O'Reilly's
Postfix "The Definitive Guide", I've visited postfix.org and the postfix
Wiki. I've read FAQs, documentation and how to's over the last few days. I
hate to say it but I need help with what looks like a very simple concept.
It is possible that I may be trying to do something with Postfix that it
just wasn't designed to do or it could be that I'm just not setting up the
syntax properly. I know from my reading that this is not a new question for
you guys and I truly appreciate your patience. Consider me a very slow
learner.

We have approxmately 25 internal servers that "feed" our postfix server.
Our server sends mail out based on the customers requests/needs (no spam).
The mail is actually requested by the recipient. However, I need to be able
to hide our internal servers & ip addresses. I've included the output from
an email I've sent myself from one of our internal servers:

Received: from mailhost.liveworld.com ([64.127.119.252]) by liveworld.com ;
Wed, 04 May 2005 15:08:01 -0700
Received: from resin7.backend.liveworld.com (resin7.backend.liveworld.com
[10.1.19.137])
by mailhost.liveworld.com (Postfix) with ESMTP id 43F834208E5
for <cmallon@liveworld.com>; Wed, 4 May 2005 15:07:59 -0700 (PDT)
Received: from resin7.backend.liveworld.com (localhost [127.0.0.1])
by resin7.backend.liveworld.com (8.12.10+Sun/8.12.10) with ESMTP id
j44M7wCJ001495
for <cmallon@liveworld.com>; Wed, 4 May 2005 15:07:58 -0700 (PDT)
Received: (from cmallon@localhost)
by resin7.backend.liveworld.com (8.12.10+Sun/8.12.10/Submit) id
j44M7w0P001494
for cmallon@liveworld.com; Wed, 4 May 2005 15:07:58 -0700 (PDT)
Date: Wed, 4 May 2005 15:07:58 -0700 (PDT)
From: C Mallon Engineering <cmallon@liveworld.com>
Message-Id: <200505042207.j44M7w0P001494@resin7.backend.livewo rld.com>
Subject: testing header_checks
Content-Type: text
To: undisclosed-recipients:;
X-Rcpt-To: <cmallon@liveworld.com>
Return-Path: <cmallon@liveworld.com>
X-DPOP: Version number supressed
X-UIDL: 1115244737.189757
Status: U

What I want to do is 1. Hide resin7.backend.liveworld.com (in fact I want to
hide "backend.liveworld.com" all together. 2.I also want to hide the ip
addresses. I do want to keep mailhost.liveworld.com (that's fine - I'm not
looking to disguise who we are, I just want to shield our internal
information).
I've tried Masquerading, I've tried masquerading_classes and I've tried
playing with header checks and nothing works. To make matters worse, it
appears that I've affected the "To:" field which now reflects "to
undisclosed reciepients".

Can someone tell me what I'm doing wrong?

I'm including the output of postconf -n:

mailhost:/etc/postfix root# postfix reload
postfix/postfix-script: refreshing the Postfix mail system
mailhost:/etc/postfix root# postconf -n
always_bcc =
append_at_myorigin = no
append_dot_mydomain = no
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
enable_server_options = yes
header_checks = regexp:/^received:.*64\.10/ ignore [THIS DID NOT WORK - IT
STOPPED MY SERVER WHICH WAS VERY BAD SO IT IS CURRENTLY COMMENTED OUT]
inet_interfaces = all
luser_relay =
mail_owner = postfix
mailbox_transport = cyrus
mailq_path = /usr/bin/mailq
manpage_directory = /usr/share/man
maps_rbl_domains =
masquerade_domains = liveworld.com
message_size_limit = 10240000
mydestination = $myhostname,localhost.$mydomain
mydomain = backend.liveworld.com
mydomain_fallback = localhost
myhostname = mailhost.liveworld.com
mynetworks = 127.0.0.1/32,11.2.0.0/16,192.166.3.0/24,172.1.0.0/255.242.0.0
mynetworks_style = host
myorigin = mailhost.liveworld.com
newaliases_path = /usr/bin/newaliases
queue_directory = /private/var/spool/postfix
readme_directory = /usr/share/doc/postfix
relayhost =
sample_directory = /usr/share/doc/postfix/examples
sendmail_path = /usr/sbin/sendmail
setgid_group = postdrop
smtpd_client_restrictions =
smtpd_enforce_tls = no
smtpd_pw_server_security_options = none
smtpd_recipient_restrictions =
permit_mynetworks,reject_unauth_destination,permit
smtpd_sasl_auth_enable = no
smtpd_tls_loglevel = 0
smtpd_use_pw_server = no
smtpd_use_tls = no
unknown_local_recipient_reject_code = 450
mailhost:/etc/postfix root#

*Names and addresses have been changed to protect the innocent.