Hot to setup mail forwarding with LDAP/AD?

==== Required information ====
- iRedMail version: 1.9.0 (Pro)
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP (AD)
- Linux/BSD distribution name and version: CentOS 6.3
- Related log if you're reporting an issue:
====

We are using AD for creation and user authentication of mailboxes.

How can i setup mail forwarding for these accounts?

Thanks in advance