Fellow experts, I would like your thoughts:
I have a very large 2010 to 2016 migration coming up and while normally I wouldn't have any issues but I see something I'm not 100% sure about.
They currently have 11 Exchange 2010 servers but we'll focus on 4 CAS servers. Two (2) are in each Active Directory Sites.
ADSite1: 2 CAS servers with all URLs (including Autodiscover) is https://Smail.domain.com (Autodiscover Site scopes are configured)
ADSite2: 2 CAS servers with all URLs (including Autodiscover) is https://Nmail.domain.com (Autodiscover Site scopes are configured)
Currently have 2 dags (for mailbox servers in each site). i.e. no copies from one data center to the other.
they also do NOT have Outlook Anywhere Enabled yet (I know this will be required)
Customer is wanting unified name space (under my recommendation) to something like https://mail.domain.com and autodiscover to https://autodiscover.domain.com
I am also planning to do a single dag with copies of databases in each DataCenter.
So, I am planning 6 Exchange 2016 servers (3 in each location).
My question is around getting to unified name space without affecting clients before migrating.
Should I at least enable Outlook anywhere on all cas servers on 2010 and set url to https://mail.domain.com and change the autodiscover on the 2010s to https://autodiscover.domain.com before even installing the first 2016 server?
Or should I match all AD site URLs on the 3 2016 servers in each site to match the 2010 servers in each site then change the 2016 URLs post migration?
my thinking is I would change the autodiscover URLs on the 2010s, install the 2016s with all URLs to https://mail.domain.com and autodiscover to https://autodiscover.domain.com and enable outlook anywhere on 2010 and set that url to https://mail.domain.com (this would be one of the first things I would do even before installing a 2016 server).
Final note, They are getting a UC cert that will cover all of these names and their current cert already has autodiscover.domain.com.