Correo rechazado por error 552 5.2.0

Buenos días,

Seguimos teniendo problemas con el envío de correo desde cuentas de nuestro dominio a cuentas de Telefónica y terra.  No lleva ficheros adjunto.

-----Mensaje original-----
Return-Path: <MAILER-DAEMON>
X-Original-To: xxxxxx@inforem.info
Delivered-To: xxxxxxinforem.info
Received: by h1748492.stratoserver.net (Postfix)
 id D98F0C78869; Thu, 30 May 2013 12:41:53 +0200 (CEST)
Date: Thu, 30 May 2013 12:41:53 +0200 (CEST)
From: MAILER-DAEMON@h1748492.stratoserver.net (Mail Delivery System)
Subject: Undelivered Mail Returned to Sender
To: xxxxxxx@inforem.info
Auto-Submitted: auto-replied
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
 boundary="7D049C78882.1369910513/h1748492.stratoserver.net"
Message-Id: <20130530104153.D98F0C78869@h1748492.stratoserver.net>

This is the mail system at host h1748492.stratoserver.net.

I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can delete your own text from the attached returned message.

                   The mail system

<xxxxxxxxx@TELEFONICA.NET>: host tnetmx.TELEFONICA.NET[213.4.149.227] said:
    550 5.1.1 <xxxxxxxx@telefonica.net> recipient rejected (in reply to RCPT
    TO command)

 Muchas gracias