Looking for way to delete all mail sent to a non-existent mailbox

[David Geller]

We're getting junk mail for a particular, non-existent mailbox. To add
insult to injury, the sender of the spam, no surprise, isn't legitimate - so
automated messages to them telling them of the non-existent account,
themselves, bounce.

What's the best way to simply have *all* mail for a particular mailbox go to
/dev/null? I created a .qmail-{mailbox} file and simply left it blank -
hoping that would do it. Is that an appropriate, effective measure?

Thanks in advance.

-David