See:
http://www.postfix.org/ADDRESS_CLASS_README.html.
In order to receive mail for a domain:
1) List the DOMAIN in the appropriate address class (mydestination,
relay_domains, virtual_alias_domains, virtual_mailbox_domains).
2) List the RECIPIENT ADDRESS in the appropriate recipient table
(local_recipient_maps, relay_recipient_maps, virtual_alias_maps,
virtual_mailbox_domains).
Credits for the answer goes to Wietse Venema
Regards
Andy