Migrate LDAP backend to MySQL

==== Required information ====
- iRedMail version: 0.8.5
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Linux/BSD distribution name and version: Ubuntu 13.04
- Related log if you're reporting an issue:
====

Hi Zhang,

I have a mail server running on 13.04 using iRedMail v0.8.5, with a LDAP backend and maildir folders.

I would like to upgrade to Ubuntu 13.10, but I understand that LDAP will not update as the versions are incompatible.

What are the steps I would need to follow to migrade my server to a MySQL backend, retaining the maildir structure?

thanks

Wayne