Can the following be done with Postfix and LDAP?

Dear readers of my blog,

I have a “simple” question for you. I Would like to do the following, can someone that reads this and has suggestions and ideas respond to me at remko@FreeBSD.org…

I have three various mailrelays, I would like to finish off mail that shouldn’t get in at the border relays. For this I have setup LDAP so that all three relays can query this LDAP Server. To fill the LDAP I use the Virtualmin application to make this as automatic as possible.

Currently the Virtual-addresses and Aliases are all in LDAP, as well as the useraccounts that receive email. No specific tag is added for local users.

I would like to have the relays do the following:

- Receive mail from XXX
- do RBL checks
- do postscreen checks and the like
- resolve the destination address (expand alias or virtual account)
if the resolved destination address lives outside of my domain (mailforwarding accounts) i would like to deliver it there immediately.
- check whether the resolved destination address is listed as local user and send it to the internal mailserver
(The internal mailserver will receive mail for local-user and only has to do spam checks for this user, no need to expand aliases etc).

Suggestions are welcome )