I setup a hybrid migration to o365 exchange. The migration of all the mailboxes, groups and public folders is complete. There were many issues with the migration, but in the end, its all online now. During the migration process i setup ADConnect and synced AD with o365, there are currently no DirectorySync errors showing( all issues were addressed ).
I would like to decommission the on-prem node. Its a Hyper-v VM running windows 2016 ( exchange 2016 ). The AD is local to the hyper v environment. Its a small setup, 2 AD servers, a file server, sql 2016 server and iis server ( all VMs ). The host server is a stand alone server not connected to AD. The idea here is to completely remove the exchange locally, exchange is uninstalled and removed from the domain per normal removal procedures.
My concern here is that MS says you should keep the server running, even if its just acting as a relay. I need the resources back, so i need the server gone. I am also concerned about having to update it and backups. With these in mind, it needs to go. Unfortunately, microsoft says that you need the on-prem for control of the user accounts. I dont see why, local AD can service them. The ADConnect install is on the DC, not the exchange server, so syncing should continue. The email portions of the accounts is completely controllable from the o365 exchange admin. I am trying to understand the exact reason the on-prem needs to stay. Why have it setup to migrate all your data online, then demand i need to keep the local one? If this is a must, is there a way around this? I dont want to break AD and the email piece nor make this more difficult to maintain.