[lug] postfix usernames

[Ben]

I've got what must be a common setup, and a common problem. I have
postfix configured more or less out of the box on debian. Postfix gets
its userlist from the system. When I add a new user, postfix
automatically delivers mail to the new user. Great. But it also delivers
mail to internal users, such as "uucp" "proxy" and "list". Additionally,
I want to create user accounts without mail accounts. Is there a way to
have a list of invalid users, so postfix will not accept mail for them? 
With a least with some of these user accounts, postfix forwards the mail
to procmail, which then fails to deliver the mail (no mailbox), but does
not give an e-mail bounce or other error message. Seems less than ideal.


Thanks,

Ben