Email Headers Show Server's Local Domain Name

I finally got my public dns address set up for my server. Everything works great. The only problem is when I look in the header it shows the server's local domain name instead of the public one.

Return-Path: <Administrator@mydomain.com>
Delivered-To: 38-personal_email_address@personal_email_domain.com
Received: (qmail 72262 invoked from network); 24 Sep 2004 03:08:42 -0000
Received: from adsl-nXXXXX.sm.customer.centurytel.net (HELO penguin.pacc.local) (my server's IP Address)
  by personal_email_server.com with SMTP; 24 Sep 2004 03:08:42 -0000
Subject: TEST
Date: Thu, 23 Sep 2004 22:08:06 -0500
Message-ID: <E18DF4A94205CE40B10250A34F528046289D@penguin.pacc.local>
X-MS-Has-Attach:
MIME-Version: 1.0
Content-Type: multipart/alternative;
      boundary="----_=_NextPart_001_01C4A1E3.B8D4C37F"
X-MS-TNEF-Correlator:
Thread-Topic: TEST
Thread-Index: AcSh47Z0HiIXZr/bSfyOIRggrOeDnQ==
Content-class: urn:content-classes:message
From: "Administrator" <Administrator@mydomain.com>
X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0
To: <personal_email_address@personal_email_domain.com>

It should not be displaying penguin.pacc.local. That is the local FQDN. The public domain name is completely different. How can I make it show that instead? Or is this normal?