I have done Dovecot and Exim authentication by built-in Samba LDAP backend without any others LDAP servers. At least It authenticates users with passwords = its login names, for users with its password != its login names authentication is failed. I don' t know yet why.
But there are some other issues / bugs with SOGo / Openchange / Samba beta1 with Dovecot in way of IMAP. You can read my posts in mailing list here and in SOGo bug tracking system. -- [email protected] https://inverse.ca/sogo/lists
