I have tried this before using LDAP and couldn't get it to work. LDAP works for accessing the DS (Directory Store) and the contacts, calendar, tasks, etc. are a part of the IS (Information Store). I've also tried using IMAP and got basically the results as described in the original post. There is something called ADSI out there that may be of some help although I haven't been able to find any good information to tell me exactly what it is.