Next edit /etc/init.d/saslauthd and change the location of saslauthd's PID file. Change the value of PIDFILE to /var/spool/postfix/var/run/${NAME}/saslauthd.pid, so that it reads:

PIDFILE="/var/spool/postfix/var/run/${NAME}/saslauthd.pid"

Now populate your system with real users. Set the users shell to /bin/false to avoid security holes.

Next fill /etc/postfix/virtual as you like. I love Webmin for this. You can edit it directly too, of course. However, webmin does a great job.

Gotcha!: "some.domain" etc. can not equal to anything mentioned in the "mydestination" line in
/etc/postfix/main.cf

Mine has the following structure:

some.domain	virtual domain
some.other.domain	virtual domain
some.really.other.domain	virtual domain
user@some.domain		user
otheruser@some.domain	otheruser
user@some.other.domain	user
otheruser@some.other.domain	otheruser
somealias@some.other.domain	user
info@some.other.domain	someoneidontlike
info@some.domain	someoneidontlike otheruser@foo.bar
differentuser@some.domain	differentuser	differentusers@home.addres	someoneidontlike
@some.really.other.domain		someonidontlike		someoneidontlikes@home.address

and so on. So I only have to set an alias for root and postmaster in /etc/aliases. All other aliases should be in this file.

Forwarding and delivering mail to multiple addresses and so forth can (and should, I believe) be set in this file too.

I use webmin for this job (and many other jobs).

Note that in this kind of setup your users can have as many aliases as they like (untill you get sick of them), but for each user you still have to add a real user, with a home directory.

Don't forget to do

postmap /etc/postfix/virtual

when you are done.