correo devuelto

Hola, tengo una cuenta de correo en telefonica.net, al enviar un correo

el outlook express me lo devuelve con este mensaje :
This Message was undeliverable due to the following reason:

Your message was not delivered because the destination computer was
not reachable within the allowed queue period. The amount of time
a message is queued before it is returned depends on local configura-
tion parameters.

Most likely there is a network problem that prevented delivery, but
it is also possible that the computer is turned off, or does not
have a mail system running right now.

The queue containing messages destined for hotmail.com
was expired by the Postmaster of telesmtp3.mail.isp.
The following recipients did not receive your message:

pero si puedo enviarlo desde mi cuenta de Hotmail, cual puede ser el
problema?
Gracias, Javier.