Postfix with LDAP for SMTP

Hi

I have configured Postfix to send mails also configured mynetworks to white list specific servers on my LAN till now it is working fine with unauthenticated users.

but now I need to integrate it with openLDAP so that postfix server will only allow authenticated users to send mail from it & deny all other unauthenticated connections.

I found local authentication can be done using SASL but unable to find anything related to openLDAP for smtp authentication, can anyone help me with this.

thank you

JA