[exim] all mails to root

Hello.

I've this need:

I want that all emails to my domain, that is not directed to a valid user,
is redirect to another user.

How can configure this?

For example:

in my exim4 server, for domain mydomain.com , there are users: daniele,
user1, admin and for these email, deliver is normal, when someone write to
another mail address (fake@??? , pluto@??? and so on),
mail is delivered to root maildir.

Thanks in advance for any suggestion.

Daniele