I'm doing a new postfix + dovecot installation and after following workaround.org guide, to create MySQL databases and testing by logging in with mysql cli and trying to create databases as pointed by guide I stubmed on error:
CREATE command denied to user 'mailuser'@'localhost' for table 'virtual_domains'
The error is because, mailuser doesn't have permissions to create tables in mailserver DB to fix that: I had to login in MySQL server as root and issue GRANT PRIVILEGES on table, i.e.:
mysql -u root -p
mysql> GRANT ALL PRIVILEGES ON `mailserver`.* TO 'mailuser'@'localhost';