[exim] Exim4 is not looking up all pgsql servers specified

Hi,

exim4.conf.template:
plain_server:
driver = plaintext
public_name = PLAIN
server_condition = ${lookup pgsql {select some_condition from some_table
where some_condition ='$auth2' and other_condition='$auth3'}{yes}{no}}
server_set_id = $auth2
server_prompts = :
.ifndef AUTH_SERVER_ALLOW_NOTLS_PASSWORDS
server_advertise_condition = ${if eq{$tls_cipher}{}{}{*}}
.endif

exim4.conf.localmacros:
MAIN_TLS_ENABLE = true
hide pgsql_servers = some_host/some_db/some_user/some_pass:\
                               other_host/other_db/other_user/other_pass
daemon_smtp_ports = 25 : 587

If credentials for some_db are correct, it never looks up other_db even
though the first pgsql search returns NULL.
What I am trying to achieve is that if the first search is unsuccessful
(wrong credentials or failed lookup), it should continue to servers in the
pgsql_servers list. Any suggestions would be highly appreciated.

Thanks,
Hai Nguyen.