[xwiki-users] Authenticate groups of users against different servers

Hi, I have a question :). First this is my situation: I am using XWiki as the company support site and I want to be able to authenticate the company users (internal users) on XWiki using their domain name and the clients (external users) using their personal e-mail. At the moment the company users are being authenticated against an Active Directory server by their domain name. Is there a way to authenticate a group of users to a LDAP server by their e-mail addresses and another group of users to an Active Directory in a different server by their domain name? Regards, Abel