Relay when user is unknown

[Blaise Hurtlin]

Hi,

I'm trying to configure my new Postfix system. I have all my users in a 
LDAP and use virtual mailbox.

I need the following behaviour:
 - Existing users in LDAP => delivered locally (this part works fine)
 - Non-existing users => relay to another SMTP

Any idea how to do that ? thanks..

Blaise