Thanks for you help. Here's the files:
/etc/postfix/mysql/virtual_alias_maps.cf:
user = vmail
password = xxxxxxxxxxx
hosts = 127.0.0.1
port = 3306
dbname = vmail
query = SELECT alias.goto FROM alias,domain WHERE alias.address='%s' AND alias
.domain='%d' AND alias.domain=domain.domain AND alias.active=1 AND domain.backupmx=0
AND domain.active=1
/etc/postfix/mysql/domain_alias_maps.cf
user = vmail
password = xxxxxxxxx
hosts = 127.0.0.1
port = 3306
dbname = vmail
#query = SELECT alias.goto FROM alias,alias_domain,domain WHERE alias_domain.a
lias_domain='%d' AND alias.address=CONCAT('%u', '@', alias_domain.target_domain) AND
alias_domain.target_domain=domain.domain AND alias.active=1 AND alias_domain.active
=1 AND domain.backupmx=0
query = SELECT mailbox.username as goto FROM mailbox,alias_domain,domain WHERE
alias_domain.alias_domain='%d' AND mailbox.username=CONCAT('%u', '@', alias_domain.
target_domain) AND alias_domain.target_domain=domain.domain AND mailbox.active=1 AND
alias_domain.active=1 AND domain.backupmx=0
/etc/postfix/mysql/domain_alias_maps_alias.cf
user = vmail
password = xxxxxxxx
hosts = 127.0.0.1
port = 3306
dbname = vmail
query = SELECT alias.goto FROM alias,alias_domain,domain WHERE alias_domain.al
ias_domain='%d' AND alias.address=CONCAT('%u', '@', alias_domain.target_domain) AND
alias_domain.target_domain=domain.domain AND alias.active=1 AND alias_domain.active=
1 AND domain.backupmx=0
/etc/postfix/mysql/catchall_maps.cf
user = vmail
password = xxxxxx
hosts = 127.0.0.1
port = 3306
dbname = vmail
query = SELECT alias.goto FROM alias,domain WHERE alias.address='%d' AND alias
.address=domain.domain AND alias.active=1 AND domain.active=1 AND domain.backupmx=0
/etc/postfix/mysql/domain_alias_catchall_maps.cf
user = vmail
password = xxxxxxx
hosts = 127.0.0.1
port = 3306
dbname = vmail
query = SELECT alias.goto FROM alias,alias_domain,domain WHERE alias_domain.al
ias_domain='%d' AND alias.address=alias_domain.target_domain AND alias_domain.target
_domain=domain.domain AND alias.active=1 AND alias_domain.active=1