Zarafa Server Management is a designed for provisioning tenants, users and groups over a REST API. It has a direct link to a preconfigured LDAP directory where all the resources are provisioned. Next to the link to the LDAP directory the product connects to the Zarafa Server components for accessing the mailbox of the users. With an advanced ACL system, administration delegation can be configured.
Disclaimer: Zarafa Server Management API is still in development stage. Using this product in production is for own risk, Zarafa B.V. can not be held responsible for dataloss or issues caused by the product.
More information can be found in the Zarafa wiki:
http://www.zarafa.com/wiki/index.php/Zarafa_Server_Management_Server_API_Installation