Postfix no servidor com múltiplos endereços IP envia emails com HELO errado no cabeçalho

Question

Eu tenho um VPS com vários endereços IP:

• venet0: 0 x.x.x.2
• venet0: 1 x.x.x.3
• venet0: 2 x.x.x.4
• venet0: 3 x.x.x.5

Todos os IPs têm registros A

• m2.domain.com - > x.x.x.2
• m3.domain.com - > x.x.x.3
• m4.domain.com - > x.x.x.4
• m5.domain.com - > x.x.x.5

e registros rDNS

• x.x.x.2 - > m2.domain.com
• x.x.x.3 - > m3.domain.com
• x.x.x.4 - > m4.domain.com
• x.x.x.5 - > m5.domain.com

Eu instalei o postfix + dovecot + mysql + opendkim.

Aqui faz parte do meu master.cf que inicia o SMTP:

x.x.x.2:smtp  inet  n  - - - -  smtpd -o myhostname=m2.domain.com
x.x.x.3:smtp  inet  n  - - - -  smtpd -o myhostname=m3.domain.com
x.x.x.4:smtp  inet  n  - - - -  smtpd -o myhostname=m4.domain.com
x.x.x.5:smtp  inet  n  - - - -  smtpd -o myhostname=m5.domain.com

Quando faço telnet para m2.domain.com:25 , obtenho o esperado HELO m2.domain.com e assim por diante para todos os subdomínios.

Tudo bem, mas no cabeçalho da mensagem eu tenho errado HELO X-Spam-Last-External-HELO: localhost.localdomain.

Eu não defini $ mydomain em main.cf e os valores de master.cf não o substituíram.

Como eu configuro o HELO dinamicamente para todos os IPs?

Aqui está um cabeçalho completo

Received: by mail-tester.com (Postfix, from userid 500) id 5E7229FFAC;
    Thu, 26 Mar 2015 23:06:15 +0100 (CET)
Authentication-Results: mail-tester.com; dkim=pass  reason="1024-bit key;
 unprotected key/testing"   header.d=domain.com [email protected]
 header.b=ow7oSJaj; dkim-adsp=pass; dkim-atps=neutral
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on mail-tester.com
X-Spam-Level: 
X-Spam-Status: No/-0.7/5.0
X-Spam-Test-Scores: DKIM_SIGNED=0.1,DKIM_VALID=-0.1,DKIM_VALID_AU=-0.1,
    RP_MATCHES_RCVD=-0.55,SPF_PASS=-0.001
X-Spam-Last-External-IP: x.x.x.2
X-Spam-Last-External-HELO: sender.localdomain
X-Spam-Last-External-rDNS: m2.domain.com
X-Spam-Date-of-Scan: Thu, 26 Mar 2015 23:06:15 +0100
X-Spam-Report: * -0.0 SPF_PASS SPF: sender matches SPF record   * -0.6
 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain   *  0.1
 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily    *     
 valid  * -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from
 author's   *       domain  * -0.1 DKIM_VALID Message has at least one valid
 DKIM or DK signature
Received-SPF: Pass (sender SPF authorized) identity=mailfrom;
 client-ip=x.x.x.2; helo=sender.localdomain;
 [email protected]; [email protected]
Authentication-Results: mail-tester.com; dmarc=pass
 header.from=domain.com
Received: from sender.localdomain (m2.domain.com [x.x.x.2])
    by mail-tester.com (Postfix) with ESMTPS id 21A759FF80
    for <[email protected]>; Thu, 26 Mar 2015 23:06:13 +0100 (CET)
Received: from [10.11.12.128] (unknown [93.123.22.36])
    by m2.domain.com (Postfix) with ESMTPA id E5B0E60CFF
    for <[email protected]>; Thu, 26 Mar 2015 18:06:16 -0400 (EDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=domain.com;
    s=mail; t=1427407577;   bh=ipEvgup1uxRHqlEp4/qod7d0wSHd0KX41Jx5NvOQe28=;
    h=Date:From:To:Subject:From;
    b=ow7oSJajrfdEy0naxO6E6KlXsVcjQ6k2josh4mlxj65cMZU/bKJSzwjUb+dvVmkNw
     zwcfgsPCe7OSJ/J2CupvfgNVV/DfpIV94UBOAv8yH9tYgRYZJlJy7xNZ3louzQVQ9j
     6TxCwC4ITnsWykNJEcxrVuorNo9FMSDpU3ynemko=
Message-ID: <[email protected]>
Date: Fri, 27 Mar 2015 00:06:16 +0200
From: bizportal <[email protected]>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101
 Icedove/31.5.0
MIME-Version: 1.0
To: [email protected]
Subject: my email test
Return-Path: [email protected]
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: quoted-printable

Editar:

Eu vi os links relacionados, mas o problema é que todos os emails de saída serão de um domínio (domain.com), portanto, mapas de transporte e várias instâncias não farão o trabalho ou não vejo como.