Hi, folks!

I have a tricky problem.
Zimbra 8.0.1 community version 64bit, Ubuntu 12.04 LTS 64bit.
Everything goes smooth over a month already since installation, but now i can see that a couple of messages are deferred by remote host.
My ISP set up an reverse DNS entry for my mx record, so using Reverse Lookup - MxToolbox everything looks perfect.
BUT, there are a couple of paranoid sysadmins, that checks all the message header and rejects it, if there is mentioned a word "localhost".
Found out, that in email header my email server is sending:
Received: from localhost (ip6-localhost [])
by mail.domain.org (Postfix) with ESMTP id 938C111E607D
for <user@userdomain.org>; Fri, 1 Feb 2013 17:54:53 +0200 (EET)
X-Virus-Scanned: amavisd-new at mail.domain.org
Received: from mail.domain.org ([])
by localhost (mail.domain.org []) (amavisd-new, port 10026)
with ESMTP id clJz9pqu7G7A for <user@userdomain.org>;
Fri, 1 Feb 2013 17:54:53 +0200 (EET)
Received: from mail.domain.org (mail.domain.org [XXX.XXX.XXX.XXX])
by mail.domain.org (Postfix) with ESMTP id E8E5111E5ECA
for <user@userdomain.org>; Fri, 1 Feb 2013 17:54:52 +0200 (EET)

So i would like to find out how to remove these header lines or replace localhost or with FQDN?!
Any ideas?