mdbox for iRedMail

==== ==== Required information ====
- iRedMail version: 0.8.3
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Linux/BSD distribution name and version: Ubuntu
- Related log if you're reporting an issue:
====

Hi,

I would like to use mdbox to reduce file numbers on my mail system. I have searched and tried

http://wiki2.dovecot.org/MailLocation/dbox

but no success. iRedMail still uses Maildir.

I have modified dovecot.conf:

# Mail location and mailbox format.
#mail_location = maildir:/%Lh/Maildir/:INDEX=/%Lh/Maildir/
mail_location = mdbox:/%Lh/mdbox/

Is %L means 'lowercase', %h means 'home directory'?

Could you please tell me way to do that?