We currently have a domain controller (server) and another domain controller, AD not in use, that hosts exchange (mailserver). we have win2k on both and the exchange is 5.5. we have no replication of any kind and all we do is map our mail accounts to an NT user. we are looking to have a backup for our AD and upgrade exchange to 2000. what would be the ideal replication/synchronization scheme for our situation? we would like to replicate AD to our member server, and we need to keep exchange up to date with synchronization of its information. i'm thinking we have exchange on mailserver sync with active directory on the main server, and that AD would in turn right back to the mailserver/AD backup. would this be a good idea?