I do this all the time and have never had an issue. Basically we have a couple of Exchange 2013 servers in a DAG with 2 DBs. One DB is for regular size mailboxes and the other is for large mailboxes. When a user needs more mailbox space, we typically just migrate their mailbox to the large mailbox DB. Today, we did this for a user and since then the user cannot connect to the exchange server with Outlook. I've tried creating a new Outlook profile and it hangs at the "log on to server" part of the connection. I get success checkmarks for "establish network connection" and "search for firstname.lastname@example.org on server settings" but it just hangs at "log on to server". As soon as I am prompted if I want to configure a mailbox, I receive a dialogue box saying a "restart will be required" but then this goes away and the connection hangs. Any ideas would be appreciated.