Using James Server 3 with LDAP

Using James Server 3 with LDAP

I want to use Apache James server with Active Directory (AD). I have
commented out the JPA users repository and enabled the LDAP configuration
in usersrepository.xml as follows:
<repository name="LocalUsers"
class="org.apache.james.user.ldap.ReadOnlyUsersLDAPRepository"
ldapHost="ldap://101.102.103.10:389"
principal="myadmin@mydomain.org"
credentials="myadminpwd" userBase="ou=NISA,dc=nisa,dc=org"
userObjectClass="user"
userIdAttribute="sAMAccountName">
</repository>
I have also added the mydomain.org to the JPA based database. But when I
try to connect to the James 3 server from javamail application, am getting
an Authentication Failed error. Has anyone got to work with James server 3
and LDAP?
I am stuck here for over a week. Checked the James server website
regarding this but nothing important is there regarding James and LDAP.