I am in the process of performing a double migration from Exchange 2003 to 2010 and then from 2010 to 2016.
I have already migrated everyone off of Exchange 2003 and have decommissioned it.
I am in the process of migrating everyone over from Exchange 2010 to 2016 and have migrated about 2/3rd of users to 2016
Haven't had any major issues with the migration thus far, but came across an issue for one user.
After migrating this users Outlook 2016 will not reconnected to the new server because it get the settings from auto discovery.
Same goes from off premise and on multiple computers.
Testing autodiscovery with the users email address, it comes back stating that it can't find the settings.
If I use one of the users proxy email address, the tests come back fine.
So I created a new profile in Outlook and used one of their proxy addresses and it is working fine, on premise and off premise.
Not quite sure what is going on with it, but i would prefer this person to use their primary email account (SAM @ domain.com) instead of a proxy address when having to connect to the exchange server.
Logging into OWA with his SAM name works fine.