Error de envio

Saludos:
Cada vez que trato de escribir un correo a un dominio especifico, me sale el
siguiente error:
" The following recipient(s) could not be reached: direccion@dominioreceptor
on 6/14/2004 2:06 PM

There was a SMTP communication problem with the recipient's email server.
Please contact your system administrator.

<dominioemisor.com #5.5.0 smtp;550 Unknown local part directo in
direccion@dominioreceptor> "

Ademas consultando en www.dnsreport.com en el reporte que emite en la
parte de Connect to mail servers, aparece:

ERROR: I could not complete a connection to any of your mailservers!

mail.moviliza.com.ec: Timed out [Last data sent: RCPT TO: ]

If this is a timeout problem, note that the DNS report only waits about 30
seconds for responses, so your mail may work fine in this case but you will
need to use testing tools specifically designed for such situations.



Yo no tengo configurado ninguna restricción de envio para los usuarios, que
podria estar pasando??