==== Required information ====
- iRedMail version: 1.8.1
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):
- Linux/BSD distribution name and version: Ubuntu 10.04
- Related log if you're reporting an issue:
====

Hello, I have a problem with a customer that sends mail via Exchange (local Exchange -> smtp out use my iredmail service).
The only problem is my client, because it all works from webmail. But if I can solve is better, as with the previous manager had no problem with the same configuration.

This is a test log from mail-tester.com .. say all ok ..

Received: by mail-tester.com (Postfix, from userid 500)    id 36D1B1C814C;
    Mon, 31 Mar 2014 09:47:03 +0200 (CEST)
X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on mail-tester.com
X-Spam-Level: *
X-Spam-Status: No/1.1/5.0
X-Spam-Test-Scores: DKIM_ADSP_ALL=1.1,SPF_PASS=-0.001,TVD_SPACE_RATIO=0.001
X-Spam-Last-External-IP: 88.198.xx.x
X-Spam-Last-External-HELO: mx.xxxxxx.it
X-Spam-Last-External-RDNS: mx.xxxxxx.it
X-Spam-Date-of-Scan: Mon, 31 Mar 2014 09:47:03 +0200
Received: from mx.xxxxxx.it (mx.xxxxxx.it [88.198.xx.x])
    by mail-tester.com (Postfix) with ESMTPS id 0F68F1C8127
    for <web-XXXXmv@mail-tester.com>; Mon, 31 Mar 2014 09:47:00 +0200 (CEST)
Received: from localhost (localhost [127.0.0.1])    by mx.xxxxxx.it (Postfix)
    with ESMTP id A9039CE2369    for <web-XXXXmv@mail-tester.com>;
    Mon, 31 Mar 2014 09:50:19 +0200 (CEST)
X-Virus-Scanned: Debian amavisd-new at
    static.88-198-xx-x.clients.your-server.de
Received: from mx.xxxxxx.it ([127.0.0.1])
    by localhost (mx.xxxxxx.it [127.0.0.1]) (amavisd-new, port 10024)
    with ESMTP id ufx6Im4gOkl4 for <web-XXXXmv@mail-tester.com>;
    Mon, 31 Mar 2014 09:50:19 +0200 (CEST)
Received: from remote.wrxxxxxx.it (host105-xx-static.xxx-95-b.business.telecomitalia.it [95.xxx.xx.105])
    by mx.xxxxxx.it (Postfix) with ESMTPSA id 37EC1CE1E4F
    for <web-XXXXmv@mail-tester.com>; Mon, 31 Mar 2014 09:50:18 +0200 (CEST)
Received: from wrxxxxxSRV.wrxxxxx.local ([fe80::3c48:cc8c:860a:205])
    by wrxxxxxSRV.wrxxxxx.local ([fe80::3c48:cc8c:860a:205%12]) with mapi
    id 14.03.0146.000; Mon, 31 Mar 2014 09:51:56 +0200
From: Tiziano Fanxxxel <t.fanxxxel@wrxxxxxx.it>
To: "'web-XXXXmv@mail-tester.com'" <web-XXXXmv@mail-tester.com>
Subject: Prova
Thread-Topic: Prova
Thread-Index: Ac9MthXFzJWi9BKUSGeudUJyYH17EA==
Date: Mon, 31 Mar 2014 07:51:55 +0000
Message-ID: <CC83D88F03D79A4187DD800E57BD491AE93A1A@wrxxxxxSRV.wrxxxxx.local>
Accept-Language: it-IT, en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [fe80::3c48:cc8c:860a:205]
Return-Path: t.fantinel@wrxxxxxx.it
MIME-Version: 1.0
Content-Language: en-US
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable

But if you send an email to his client that uses a corporate SMTP server:
mail.xxxxxxxxx.it #<mail.xxxxxxx.it #5.0.0 smtp; 550 Requested action not taken: mailbox unavailable> #SMTP#

But mail exists ... this is the log of return mail:

Return-Path: <t.fantixxx@wrxxxxxx.it>
Received: from localhost (localhost [127.0.0.1])        by mx.txxxxx.it (Postfix)
with ESMTP id 9F3DECE3740       for <paolo@renatoxxxxxxxxx.it>; Mon, 31 Mar 2014
10:54:06 +0200 (CEST)
X-Virus-Scanned: Debian amavisd-new at
        static.88-xxx-xx-x.clients.your-server.de
Received: from mx.txxxxx.it ([127.0.0.1])       by localhost (mx.txxxxx.it
[127.0.0.1]) (amavisd-new, port 10024)  with ESMTP id KEjHbJiP81Q0 for
<paolo@renatoxxxxxxxxx.it>;     Mon, 31 Mar 2014 10:54:05 +0200 (CEST)
Received: from remote.wrxxxxxx.it
(hostxxx-xx-static.xxx-95-b.business.telecomitalia.it [xx.xx.xx.105])  by
mx.txxxxx.it (Postfix) with ESMTPSA id 14360CE2369;     Mon, 31 Mar 2014 10:54:01
+0200 (CEST)
From: Tiziano xxxxinel <t.fantixxx@wrxxxxxx.it>
To: Paolo xxxxgatti <paoxx@renatoxxxxxxxxx.it>
Subject: PHmetro finale installato
Thread-Topic: PHmetro finale installato
Thread-Index: Ac9Mvrz31YVJmtErT/uD9p/tBzGgbw==
Disposition-Notification-To: Tizixxx xxxtinel <t.fantxxxx@wrxxxxxx.it>
Return-Receipt-To: <t.fantxxxx@wrxxxxxx.it>
Date: Mon, 31 Mar 2014 08:55:39 +0000
Message-ID: <CC83D88F03D79A4187DD800E57BD491AE93A7F@wrxxxxxxSRV.wrxxxxxx.local>
Accept-Language: it-IT, en-US
Content-Language: it-IT
X-MS-Has-Attach: yes
X-MS-TNEF-Correlator:
x-originating-ip: [192.168.10.11]
Content-Type: multipart/related;
        boundary="_004_CC83D88F03D79A4187DD800E57BD491AE93A7FwrxxxxxxSRVwrital_";
        type="multipart/alternative"
MIME-Version: 1.0

it seems that the message is non-existent email spam protection.
I tried to remove the header written with "local" but no work.

No idea? It seems exchange causes trouble.