I get this message only when I try to send email only to one email address but it general it works fine. This is my side or others?

I reproduce here the complete header:

De:  mailer-daemon@mail.zoho.com  [mailto: mailer-daemon@mail.zoho.com ]
Enviado el: lunes, 02 de noviembre de 2015 11:03
Para:  jlmartinez@corebc.es
Asunto: 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.

xxxxxxx@ohl.es  Error, ERROR_CODE :500, ERROR_CODE :5.5.1 Command unrecognized: ""


 Received:from JUANPC ( 4.187.219.87.dynamic.jazztel.es  [87.219.187.4]) by  mx.zohomail.com
        with SMTPS id 1446457581536896.3038707704046 ; Mon, 2 Nov 2015 01:46:21 -0800 (PST)
 Message-ID:<003601d11553$53d4 8300$fb7d8900$@es>
 Date:Mon, 2 Nov 2015 10:46:16 +0100
 From:Juan Luis Martínez < jlmartinez@corebc.es >
 To:'xxxxxxxxxxx' < xxxxxxxxx@ohl.es >
 Subject:un mail de prueba
 Content-Type:multipart/relate d;
        boundary="----=_NextPart_000_0 037_01D1155B.B598EB00"

Any help it would be much appreciated.

Thanks