[Exim] Virtual blocking

Hi All,

I have been playing around with virtula domains and alias files but I am
not really getting anyware, and now I am feeling that I am not taking
the right approach. I run exim (4.2) with a number of domains however at
the moment the domains all map to local users for mail, but now I have
two users on different domains with the same name --- I want to receive
mail for fred@??? but not fred@???

Any pointers????

In short
fred@??? ----> fred (local user)
fred@??? ---> user not known

Please

Wayne