This particular functionality of OpenLDAP should be of special interest for environments where long term co-existence between OpenLDAP and Active Directory is required. By establishing pass-through authentication the following advantages could be achieved: Great end-user experience. No need to remember multiple passwords Increased security, due to the reduction of the attack surface (one less password store in the environment) Single password policy The rest of the post will expand on the instructions provided by the OpenLDAP 2.4 Administration guide on establishing pass-through authentication from OpenLDAP to Active Directory. Specifically, will will leverage the capability of SASL to use LDAP as an authentication back-end. In our case, Active Directory will play a role of such authentication back-end. - Matteo Marchelli