When you use only mail users from the ldap with multiple email domains the vhost is only filled with the mailserver domain itself.
Therefore when you receive email on a alias domain or other domain it does not accept it.
It should check the ldap if the domain is defined and accept email for it.

It seems that the table for defining domains in the ldap is missing. What is the correct solution:

1. Expand the ldap postfixbook scheme and add it to the virtual domain lookup?
2. Create a tool that reads all mail addresses from the ldap to retrieve the domain?