CREATE USER 'postfix'@'localhost' IDENTIFIED BY 'POSTFIXPASS';
GRANT SELECT ON 'postfix'.* TO 'postfix'@'localhost';

CREATE USER 'dovecot'@'localhost' IDENTIFIED BY 'DOVECOTPASS';
GRANT SELECT ON postfix.mailbox TO 'dovecot'@'localhost';
GRANT SELECT,INSERT,UPDATE,DELETE ON postfix.quota2 TO 'dovecot'@'localhost';