Local address verification for remote domains

[Kent Oyer]

I have a Postfix server that is a mail gateway for a remote domain. The domain is setup as a relay domain (in relay_domains) and I have the final destination defined in transport_maps. That part is working fine. However, I would like to use recipient address verification to reject invalid recipient addresses BUT instead of probing the remote server, I have a local database of valid users. I was looking at using address_verify_transport_maps to force it to use a local or virtual lookup table but I can't figure it out. Here is what I have so far:

/etc/postfix/main.cf
relay_domains = hash:/etc/postfix/relay_domains
transport_maps = hash:/etc/postfix/transport
address_verify_transport_maps = hash:/etc/postfix/address_verify_transport
virtual_mailbox_base = /var/mail/vhosts
virtual_mailbox_maps = hash:/etc/postfix/vmailbox

/etc/postfix/relay_domains
example.com OK

/etc/postfix/transport
example.com smtp:[1.2.3.4]


/etc/postfix/address_verify_transport
example.com virtual:

/etc/postfix/vmailbox
us...@example.com bogus/
us...@example.com bogus/


When I try to send a test message to us...@example.com I get an error:

450 4.1.1 <us...@example.com>: Recipient address rejected: unverified address: mail system configuration error

The directory /var/mail/vhosts/bogus exists but no mail should ever be delivered to it because I'm only using it for address verification. The actual mail gets delivered to the remote server at 1.2.3.4

What am I missing?

Thanks
Kent