You can use tool script in iRedMail to import user accounts: http://iredmail.googlecode.com/hg/iRedMail/tools/ (File name: create_mail_user_OpenLDAP.py).

Users can set mail forwarding in Roundcube webmail in 'Filter' table.

What do you mean 'get stats of users with no mail forwarding'?

For the mail fowarding, i need a global forwarding without keeping a copy of mail on the server.

I tried your import script. I've no error message. the file ldif seems ok. but nothing in the vmail folder. It's for a virtual domain.

Thanks

There is nothing in iRedAdmin and login via roundcubemail fail.

I think the problem is here :
# Prompt to import user data.
'''
Would you like to import them now?""" % (ldif_file)

answer = raw_input('[Y|n] ').lower().strip()

if answer == '' or answer == 'y':
    # Import data.
    conn = ldap.initialize(LDAP_URI)
    conn.set_option(ldap.OPT_PROTOCOL_VERSION, 3)   # Use LDAP v3
    conn.bind_s(BINDDN, BINDPW)
    conn.unbind()
else:
    pass
'''