ccc_cdxxb's questions

We're migrating from 2013 to 2019 and so far everything is going well. I've moved a good set of our user mailboxes with no issues and connectivity, mail flow, etc.

What I keep running into is these hidden arbitration mailboxes that I had no clue existed that need to be migrated and this got me thinking about what else I need to migrate before decommissioning our 2013 instance.

Currently, I'm aware of migrating: User, Room Resource, Shared Mailboxes. Public Folders.

Is there a comprehensive list of what needs to migrated and what doesn't? Is there command I should be running right before our 2013 instance is uninstalled and decommissioned to catch these things and migrate them?

I've been scouring the internet to try to find anything but most articles just simply say move all your mailboxes and public folders, turn off 2013 for a week. Then turn it back on if there are no issues and run the uninstaller to remove 2013 from the domain appropriately.

Our current domain is at a functional level 2008 R2 and all the current domain controllers are built on Windows Server 2008 R2 OS. One of our remote site domain controllers is up for replacement and we are looking at deploying a domain controller with Windows Server 2012 R2 OS.

Are there any "gotcha's" or things to be aware of? I understand it will likely bring the domain level up to a mixed mode but is there anything that absolutely will not work with this set up? It seems pretty straightforward with just installing the role and then running dcpromo through Server Manager. I remember how difficult the jump from 2003 functional level to 2008 R2 functional level was and just want to be sure running in this mixed mode won't cause an even bigger headache.

I have looked at Technet and not seen anything that seems too difficult or dangerous.

Current environment: Two Windows Server 2003 servers, not joined to our domain (These are here to handle our outside DNS requests).

Plan: Stand up Windows Server 2012 R2 server, do not join to our domain. Give IP and install DNS role on server. Mark server as slave to our master DNS server which is Windows Server 2003. Once replication is complete, mark 2012 R2 DNS server as master. Build secondary DNS server on 2012 R2 platform, join as slave to 2012 R2 master. Then decommission 2003 DNS servers.

My question is, are there any "gotchas" or issue with this plan? Will there be compatibility issues between the 2003 server and the 2012 R2 server? Is our plan viable? I have been searching around and have not found anything about doing this either from Microsoft or from one of their partners.