Query my postfix aliases file as a LDAP server?

[Evan Platt]

My primary MX record for my domain is an anti-spam server. This server 
then delivers to my mail server (so basically my postfix and firewall 
only allow smtp connections from a few IP's).

However the problem is the anti-spam server essentially allows anything 
at my domain - [EMAIL PROTECTED], etc. I maintain a list of allowed 
aliases in postfix - /etc/postfix/aliases. My anti-spam server can query 
an ldap server, and then reject at SMTP time, any invalid e-mail 
addresses. So basically, is there a way for postfix to act as a LDAPS 
server and allow a outside server query to check if a alias is valid?

Hope this makes sense...  I'm running Postfix 2.1.5 - I can obviously 
provide my postconf -n, but not sure that's needed..

Thanks. :)

Evan