[exim] Impossible to send mail without domain...

Hello.

I don't understand. I try tout send local mail whitout domain extension and
it's fail everytime.
I read on the doc: "in a locally submitted message, if an unqualified address
(that is local part without address) is found in the enveloppe, it is
qualified using the domain defined by qualified_domain"
Where is the problem?

exim4 -bv foo
foo@ failed to verify:
mail domain "" is syntactically invalid

Thanks for your help

Erick.B