LDAP Authentication with Samba 4 Active Directories

Hello,

Has anyone managed to setup successfully user authentication via Samba 4 
AD LDAP?

I have followed some threads I found with google, but unfortunately 
without success.

If I leave bind_dn and bind_pw empty, dbmail-imapd starts, but the no 
user can get authenticated. Also dbmail-users -l returns an empty list 
(users have all the indicated fields in the LDAP record, like mail, etc).

If instead I provide a dn and password to bind to the LDAP server, 
dbmail-imapd always fails with the following:


dbmail/imap4d[21704]: Error:[auth] auth_ldap_bind(+151): ldap_bind_s 
failed: Strong(er) authentication required
dbmail/imap4d[21704]: Error:[server] server_run(+777): could not connect 
to authentication


Thank you in advance,

Mauro