[exim] Removing the local_user Router

A little Sunday afternoon tweaking has me wondering. I've got these
two routers at the end of the routers section:

    procmail:
      debug_print = "R: procmail for $local_part@$domain"
      driver = accept
      check_local_user
      transport = procmail_pipe
      require_files = ${local_part}:${home}/.procmailrc:+/usr/bin/procmail
      no_verify
      no_expn

    local_user:
      debug_print = "R: local_user for $local_part@$domain"
      driver = accept
      check_local_user
      local_parts = ! root
      transport = LOCAL_DELIVERY

I've been seeing a lot more spam sent to "users" that are in my alias
and passwd files (i.e. www-data).

All my real users use procmail for delivery, so I thought maybe I
could remove the "local_user" router and only accept mail for users
with a .procmailrc file.

But testing without the "local_user" router all my users report
"Unrouteable address". Not sure I understand why that happens. All
my local deliveries are reported with R=procmail T=procmail.

What I'd like is if there's an alias that points to a user with a
.procmailrc file, then deliver. Otherwise reject.

And, I'd also like to prevent mail getting delivered to "users" just
because they are listed in /etc/passwd but don't have a .procmailrc
file.


On a related note, my Debian Stable system comes with an /etc/aliases
file that includes entries like:

    mail: root
    news: root
    uucp: root
    proxy: root
    www-data: root
    mailer-daemon: postmaster

I'm not clear, but when does mail get delivered to those? Why would I
ever accept mail for, say, my web server?


--
Bill Moseley
moseley@???