E-mails que regresan...

Hola a todos.
Luego de la migración del servidor exchange, outlook 2003 da los
siguientes errores, a veces el envío de e-mails funciona, y aveces este
falla con el mensaje de error siguiente:

Some internal emails are bouncing back. Examples:

=>
Your message did not reach some or all of the intended recipients.

Subject: Please produce four PositionPavillion SKUs
Sent: 1/6/2005 2:42 PM

The following recipient(s) could not be reached:

Eugenia Carola on 1/6/2005 2:42 PM
The message could not be delivered because the recipient's destination
email system is unknown or invalid. Please check the address and try
again, or contact your system administrator to verify connectivity to the
email system of the recipient.
<paris165.dom.cnt#5.1.2>

>
Alguien tiene una idea cómo reparar el error?

Muchas gracias.
Hnepat