Outllook 2013 Exchange Active Sync (EAS) sending error - Undelivered Mail Returned to Sender

Outllook 2013 Exchange Active Sync (EAS) sending error - Undelivered Mail Returned to Sender

Hello, we are receiving these automatic replies when sending from Outlook 2013 (setup with Exchange Active Sync) to @outlook.com, @hotmail.com, @live.com, etc.
Sending directly from the web is working.
Receiving emails is working fine also.

Here is an example of one.

Thanks!

-----Original Message-----
From: mailer-daemon@mail.zoho.com [mailto:mailer-daemon@mail.zoho.com]
Sent: lunes, 31 de agosto de 2015 9:09 p. m.
To: matias@devoto.co
Subject: Undelivered Mail Returned to Sender

This message was created automatically by mail delivery software.

 A message that you sent could not be delivered to one or more of its recipients. This is a permanent error.

xxxxxxxx@outlook.com Error, ERROR_CODE :550, ERROR_CODE :5.7.0 (BAY004-MC3F23) Message could not be delivered. Please ensure the message is RFC 5322 compliant.

 Received:from mail.zoho.com by mx.zohomail.com

         with SMTP id 144106611709964.92691704930667; Mon, 31 Aug 2015 17:08:37 -0700 (PDT)  Message-ID:<14f863be6f3.e99286c8106814.8146561015074142287@devoto.co>

 Date:Mon, 31 Aug 2015 21:08:34 -0300

 From:Matias Devoto <matias@devoto.co>

 User-Agent:Zoho Mail

 To:"'Matias Devoto'" <xxxxxxxxx@outlook.com>  Subject:Prueba 9.08 pm  Content-Type:multipart/alternative;

                boundary="----=_NextPart_000_0178_01D0E431.32C053E0"