Here's my situation:
I have one Exchange server (2013) in my current organization, running all roles. We are looking at migrating Exchange to another physical machine. Let's say I setup a second Exchange server and make it part of my organization, also running all roles.
My user's mailboxes are still stored in the database on my old Exchange server. Clearly I will want to migrate those mailboxes to the new server as part of the migration. My question is, what happens if a user connects to the new Exchange server, either by Outlook 2013, ActiveSync, or OWA, but that user's mailbox is stored on the old Exchange server? Do they simply receive an error message stating that their mailbox is unavailable, or are the two Exchange servers smart enough to 'figure out' to redirect the user to old Exchange server where his mailbox is actually stored?
The reason I ask is that I want to know how much email service disruption to expect with this migration and how much of it I will be doing after hours.
