exim4 : how to send email to local domain + address ?

[Bruno Costacurta]

Hello,
how to send email to a local mailbox ?

My config in file email-addresses is :

bruno: myemail at pt.lu
root: myemail at pt.lu

which works fine to email to external email address 
but not for local, ie. from bruno to root as I received 
   ----- The following addresses had permanent fatal errors -----
<root at pc34ghz.org>
    (reason: 550 Host unknown)

I suppose I should indicate pc34ghz.org as local domaon not to be send to my 
ISP smtp server (which is the reason of errror as my local domain is of 
course not known) but how ? 

Thanks.
Bye,
Bruno