From: Andromeda <andromeda@htmlworkshop.com> 
Date: Sun, 15 Nov 1998 23:24:05 +0200   

This approach to virtual domains has helped me a great deal, and is so easy
to maintain (add and modify as appropriate):

Under the main configuration settings (in your configure file):

local_domains = "domain1.com:mydomain.com:\
	       lsearch;/usr/exim/aliases/domains"

Under transports:

local_delivery:
  driver = appendfile
  file = /var/spool/mail/${local_part}

Under the directors settings:

system_aliases:
  except_domains = "lsearch;/usr/exim/aliases/domains"
  driver = aliasfile
  file = /etc/aliases
  search_type = lsearch

userforward:
  except_domains = "lsearch;/usr/exim/aliases/domains"
  no_verify
  driver = forwardfile
  file = .forward

localuser:
  except_domains = "lsearch;/usr/exim/aliases/domains"
  driver = localuser
  transport = local_delivery

virtual:
  domains = "lsearch;/usr/exim/aliases/domains"
  driver = aliasfile
  no_more
  file = /usr/exim/aliases/$domain-aliases
  search_type = lsearch

Voila. Done. This requires the following files from you:

1. domains (contains the domains that you do virtual hosting for. Its format is
as follows:

domain1.com
domain2.com
.
.
etc.

2. domain1.com-aliases (contains the addresses in domain1.com that you want
to redirect). The format is as follows:

bob: bob@ibm.net
adam: adam@otherdomain.com
.
.
etc.

/usr/exim/aliases/ is my directory where I store those files to make it
easier for administration.

This way it works just fine, and mail to non-existent aliases gets bounced.
You can check whether selecting *: allows you to do a catch-all.