Correo rechazado por error 552 5.2.0

Muy Buenas.

Soy el administrador del servidor de correo del dominio inzamac.es  (mail.inzamac.es=46.24.22.66)

Desde hace un mes estamos teniendo problemas con los correos que nuestros empleados mandan a dominios de mx.e.telefonica.net, o asociados a movistar o telefonica.

El error siempre se parece a algo así:

Fatal SMTP error relaying the message to server mx.e.telefonica.net: 213.4.149.253: 552 5.2.0 Hjee1m0091RZ4We07jeeZx internal error

¿Me pueden ayudar a resolverlo?

El log del servidor de correo  me devuelve la siguiente información:

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27/08/2013 9:37:46 - Starting delivery thread, ID=48306
27/08/2013 9:37:46 - { 48306} START Delivery
27/08/2013 9:37:46 - [ 48306] Delivering to 3 recipients
27/08/2013 9:37:46 - [ 48306] Attempting to deliver to the domain espina.es
27/08/2013 9:37:46 - Active delivery threads (ID=48306 start): 0
27/08/2013 9:37:46 - [ 48306] Retrieved 1 MX records for domain espina.es
27/08/2013 9:37:46 - [ 48306] Trying the server mx.e.telefonica.net: 213.4.149.253
27/08/2013 9:37:47 - [ 48306] Fatal SMTP error relaying the message to server mx.e.telefonica.net: 213.4.149.253: 552 5.2.0 Hjeb1m0011RZ4We06jebL2 internal error
27/08/2013 9:37:47 - [ 48306] Fatal SMTP Error: 552 5.2.0 Hjeb1m0011RZ4We06jebL2 internal error. Will bounce back
27/08/2013 9:37:48 - [ 48306] Attempting to deliver to the domain gwaters.e.telefonica.net
27/08/2013 9:37:48 - [ 48306] Retrieved 1 MX records for domain gwaters.e.telefonica.net
27/08/2013 9:37:48 - [ 48306] Trying the server mx.e.telefonica.net: 213.4.149.253
27/08/2013 9:37:49 - [ 48306] Fatal SMTP error relaying the message to server mx.e.telefonica.net: 213.4.149.253: 552 5.2.0 Hjed1m0071RZ4We0AjedAm internal error
27/08/2013 9:37:49 - [ 48306] Fatal SMTP Error: 552 5.2.0 Hjed1m0071RZ4We0AjedAm internal error. Will bounce back
27/08/2013 9:37:49 - [ 48306] Attempting to deliver to the domain gwaters.es
27/08/2013 9:37:49 - [ 48306] Retrieved 1 MX records for domain gwaters.es
27/08/2013 9:37:49 - [ 48306] Trying the server mx.e.telefonica.net: 213.4.149.253
27/08/2013 9:37:50 - { 48308} START POP3
27/08/2013 9:37:50 - [ 48306] Fatal SMTP error relaying the message to server mx.e.telefonica.net: 213.4.149.253: 552 5.2.0 Hjee1m0091RZ4We07jeeZx internal error
27/08/2013 9:37:50 - [ 48306] Fatal SMTP Error: 552 5.2.0 Hjee1m0091RZ4We07jeeZx internal error. Will bounce back
27/08/2013 9:37:50 - Delivery thread, ID=48306, terminated after running for 4,219 seconds.
27/08/2013 9:37:50 - { 48306} END Delivery

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