While authenticating , give the DN of the user and the password.

If mail-id is unique attribute just seach user object from directory whose mail-id
is equivalent. Then get the distinguished name according to that.

There are plenty of unique attributes in AD (userPrincipalName, samAccountName,...) that you can use
as login id.

To get user's relative distinguished name when you know eq. samAccountName
call following function.

String userRDN = getUSerRDN("samAccountName","Raipe");

Note that m_Ctx is your existing LdapContext...

 public String getUserRDN(String uniqueAtt,String user) throws NamingException{
        String ret;
        SearchControls constraints = new SearchControls();
        constraints.setSearchScope(SearchControls.SUBTREE_SCOPE);
        constraints.setReturningAttributes(new String[0]); // we are interested in rdn only
        String searchCondition = "(" + uniqueAtt + "=" + user + ")";
        
        NamingEnumeration results  = m_Ctx.search("", searchCondition, constraints);
        if (results != null && results.hasMoreElements()) {
            
                // returning first (and only)
                SearchResult si = (SearchResult)results.nextElement();
                ret = si.getName();
            
        } else
             throw new NamingException(" Cannot find RDN ");
            
       
        return ret;
    }

I want to authenticate people against Active Directory for user in Windows 2000 domain. User login from web page and get authenticate if they have their user name and password in Windows 2000 domain