We inherited a client network, which was using a hosted version of Exchange, but the client has moved back to on-premise.
We reconfigured CAS (among other things), and setup Exchange and the network. Everything went well.
But, periodically, Outlook clients revert back to the old server settings ... as if being updated by GPO. Of course, this causes client to be unable to send / receive, and we have to delete the profile, and create a new one. When you create a new exchange profile, it connects to the DC and Exchange and sets everything up correctly.
We have looked and looked, but cannot figure out what is causing this reversion.
What do we need to look at in order to find this?
Do you move mailbox to new Exchange server? If so, try to re-cycle MSExchangeAutodiscoverAppPool and MSExchangeServicesAppPool on new server's IIS Manager.