Can't receive emails to my mail server

Found this solution:

add this on /etc/dovecot/conf.d/20-lmtp.conf:

protocol lmtp {
postmaster_address = mysql:/etc/postfix/mysql-virtual-mailbox-maps.cf # required
mail_plugins = quota
}

probably this was:

protocol lmtp {
  # Space separated list of plugins to load (default is global mail_plugins).
  #mail_plugins = $mail_plugins
}