I have a Scalix user who connects via Outlook, SWA and iPhone. They can see their personal address book / contact list in Outlook (via SC4O) and in SWA (because it just works

The iPhone LDAP setup is as follows:
Server: scalix.mydomain.com
User: cn=User Name
Pword: theirpassword
Search Base: o=Scalix
I guess that this is just a case of setting a new search base for the user's personal contact list but I can't find any docs or forum posts that say how to do this. Please could someone post to say what the correct search base is? (Or have I missed the point here and there's another way to do it?)
Kind regards and thanks in advance
Matt