changing hostname and postfix

I have following problem:

I changed host name from "mgserver.mg-gaming.net" to "www.mg-gaming.net" on /etc/hosts and /etc/hostname
I also change "mgserver.mg-gaming.net" to "mg-gaming.net" in /etc/postfix/main.cf

Now, when i send mail (forum script to user) i still get old hostname on some data in mail header. Here is example:

---------------------------

Return-Path: <www-data@mgserver.mg-gaming.net>
Received: from mg-gaming.net (89-149-226-220.internetserviceteam.com [89.149.226.220])
by mx.google.com with ESMTP id k29si6251254fkk.2007.09.22.20.24.05;
Sat, 22 Sep 2007 20:24:06 -0700 (PDT)
Received-SPF: neutral (google.com: 89.149.226.220 is neither permitted nor denied by best guess record for domain of www-data@[COLOR="Red"][B]mgserver.mg-gaming.net[/B][/COLOR]) client-ip=89.149.226.220;
Authentication-Results: mx.google.com; spf=neutral smtp.mail=www-data@mgserver.mg-gaming.net
Received: by mg-gaming.net (Postfix, from userid 33)
id 844D01C25298; Sun, 23 Sep 2007 05:24:05 +0200 (CEST)

-----------------------------

I can notice that old hostname is in the mail. Where do i change this? It causes some local provider mailserver to drop mail because of non-existing sender (mgserver.mg-gaming.net) which i have to change to existing one (mg-gaming.net od www.mg-gaming.net)

 

What are the outputs of

Code:

postconf -n

and

Code:

postconf -d

?

 

I managed to find error. Hostname also needed to be changed in /etc/mailname