user = mailuser
password = mailuserpass
hosts = 127.0.0.1
dbname = mailserver
query = SELECT 1 FROM `mailserver`.`virtual_users`
	INNER JOIN `mailserver`.`virtual_domains` 
	ON `virtual_domains`.`id` = `virtual_users`.`id` 
	AND `virtual_domains`.`name` = SUBSTRING_INDEX('%s', '@', -1)
	WHERE `virtual_users`.`username` = SUBSTRING_INDEX('%s', '@', 1)