As you might already know AD does not let you change the password through LDAP if you don't have a secure connection to AD. I heard that there is a registry setting to change this behavior but so far couldn't find where it is... Anyone of you know how can I can change this behavior?
You should be able to disable this by changing the local security policy on the domain controller(s) for 'digitally signed server communications'
This can be found in
Obviously you need to be aware of the security hole you would be opening on your DC when doing this.