mysql> CREATE TABLE `virtual_aliases` (
    -> id int(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
    -> user_id INT(11) NOT NULL,
    -> destination VARCHAR(80) NOT NULL,
    -> FOREIGN KEY (user_id) REFERENCES virtual_users(id) ON DELETE CASCADE
    -> ) ENGINE = InnoDB;
ERROR 1005 (HY000): Can't create table './mailserver/virtual_aliases.frm' (errno: 150)
mysql>