dot qmail problem

[Lye On Siong Johnny]

Hi,

I am using qmail + vpopmail.
Currently, I am facing this problem. I have email account like test, 
test-a, test-b
everything works fine. However, when someone send a mail to test-c, it's 
send to test instead.
Is there anyway i can configure it such that if there isn't any valid 
account or .qmail file, then the
mail should be bounce instead of being delivered.


Please advice

Thanks
Johnny