[otrs] ldap customer auth

Hello, I've ldap authentification set up and working perfectly (thanks to all those whose tutorials were available by Google). Now I'd like (but perhaps this is simply not possible ?) to let customers login from another LDAP server (AD actually), I can see them from an admin login but when they try to login it just looks in the first LDAP server (I must point out that these ADs are completely autonomous and unrelated). It would be great if it is possible but even without OTRS is fantastic ! Thanks in advance, Adam