Problem with rmail

[luca . spinacci]

Hi,
I put the following lines in my .emacs file to get mail
on a POP3 server:
(set-variable 'rmail-primary-inbox-list
   (quote ("po:luca.spinacci@tin.it:in.virgilio.it")))
(setq rmail-pop-password-required t)

Rmail ask for the POP password...
Echo line shows: Getting mail from post office ...
but an error echos : movemail: Error connecting to POP server:
                                       Could not determine POP server's address
and:
(No new mail has arrived)

Any ideas?
Thank you,
Luca Spinacci