user=<mysql_db_user>
password=<mysql_db_password>
dbname=<mysql_db_name>
hosts=127.0.0.1:<mysql_db_port>
query = SELECT maildir FROM mailbox, alias_domain
  WHERE alias_domain.alias_domain = '%d'
  AND mailbox.username=concat('%u', '@', alias_domain.target_domain )
  AND mailbox.active = 1 AND alias_domain.active = 1