Exchange 2010 -> Exchange 2013 Migration - Final environment setup questions
I'm migrating my onsite Exchange 2010 Servers to Exchange 2013 (because we already own the licenses and it is a necessary step as we ultimately transition to cloud email in 2022). I did a full test run in my DEV environment and everything went well except for Public Folders. Still needing to figure out what I'm going to do with that. However, my concern with this inquiry is more about the actual Exchange 2013 server (and cert) setup before and after the migration. So, here we go...
Right now, I have 2 Exchange 2010 SP3 servers, with one being the primary Mailbox server (A) with all the roles and the other being used exclusively for the Exchange online archive mailboxes and Public Folder replication (B). Initially, my 2 Exchange 2013 servers are setup the same way, with both having the Mailbox and Client Access roles. One is hosting all mailboxes (C) and the other is holding the Archive mailboxes (D). I had an initial issue with autodiscovery, which seems to be a known issue. OWA worked flawlessly, but Outlook required me to delete/rename the Outlook folder within C:\Users\<username>\AppData\Local\Microsoft. Annoying, but able to be worked around for now. So, I currently have 2 Exchange 2010 and 2 Exchange 2013 servers all active. As expected, the Exchange 2010 servers don't see the Exchange 2013 servers, but the Exchange 2013 server see all servers. Right now, A is the primary server, meaning that all incoming email traffic is routed to it (mail.<domain>.com). C is currently using newmail.<domain>.com. The certificate on C and D newmail.<domain>.com, autodiscover.<domain>.com, mail.<domain>.com, C.<domain>.com and D.<domain>.com. Yeah, I don't like having the server names in the cert, but I wanted to avoid initial warnings during setup and testing. I'll update the cert once I've changed all the virtual directories to point at mail.<domain>.com. Which gets me to my primary questions. So, in 2 weeks, it is my plan to make C (2013) be the primary server. I change the NAT setup and current TXT records and that is done. However, I then have A (2010) with mail.<domain>.com as the external access to all virtual directories and A.<domain>.com for all internal access. As I will still have the vast majority of my users still on A, as I do a gradual mailbox move from A to C, I want to minimize any interruption/actions required of the users. In a preferred Exchange setup, what should the virtual directories be pointing to internally and externally? If C is in place as the primary, can I just have mail.<domain>.com everywhere and rely on autodiscovery?
I appreciate and assistance that anyone can provide.