Virtual users @ virtual domains / better documentation?

[justina colmena ~biz]

I have configured postfix so it will deliver mail to virtual mailboxes. For 
some reason, the mail is not delivered to the virtual mailboxes unless both 
$virtual_alias_domains and $virtual_alias_maps are left undefined: these 
directives are apparently for aliasing virtual users "@" virtual domains to 
"real" unix users on the local system.

--%%==
# ADDRESS REDIRECTION (VIRTUAL DOMAIN)
#
# The VIRTUAL_README document gives information about the many forms
# of domain hosting that Postfix supports.
virtual_mailbox_domains = domain1.example.org domain2.example.com
virtual_transport = virtual
#virtual_alias_domains = domain1.example.org domain2.example.com
virtual_mailbox_base = /var/mail/vhosts
virtual_mailbox_maps = hash:/etc/postfix/vmailbox
virtual_minimum_uid = 100
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
#virtual_alias_maps = hash:/etc/postfix/virtual
==%--

If the $virtual_alias_maps directive invalidates virtual mailboxes, then "the 
usual" aliases (postmaster@, etc.) for the virtual domains would have to be 
listed in
    /etc/aliases
along with the non-virtual aliases, but this does not work either, and 
generates a warning when "newaliases" is run.

postalias: warning: /etc/aliases, line 99: name must be local

So as far as I can tell, no aliasing at all is available for 
"virtual_mailbox_domains" in postfix

I am still unsure how to authenticate the virtual users on postfix. PAM 
authentication works fine for non-virtual users. The following command 
gives two options for authentication: cyrus-sasl and dovecot-sasl.

    # postconf -a
    cyrus
    dovecot

Postfix also works with cyrus-sasl if the passwords are set in "/etc/sasldb2"
via the "saslpasswd2" command, but dovecot doesn't seem to work with
cyrus-sasl, and has its own type of sasl authentication.

I realize this is not a postfix list, so my real question here is, What do I 
need in order for dovecot to authenticate the virtual users and allow them to 
read their mail and obtain authorization to send mail via postfix on the same 
system?
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