I've recently started at a new company and have taken over their Office 365 instance. The history is they had Exchange at one point. They used Skykick to migrate to Exchange Online and their consultants told them they no longer needed Exchange on-premises to manage email so they removed Exchange completely but are still using AD Connect for syncing. This has made managing email accounts somewhat painful because the on-premises Active Directory is the source of authority. This post https://jaapwesselius.com/2016/06/09/office-365-directory-synchronization-without-exchange-server/ is a lot of what we are dealing with.
What we would like to do is install Exchange back on-premises and then configure hybrid Exchange. My question is are there any gotchas on this or things to look out for? Is it possible to reintroduce Exchange to the environment without breaking anything? Any advice would be greatly appreciated.
You don’t need to offboard like another user stated. Install the Exchange server in your environment, which will require expanding your schema for it. Once that is done, check the box in AAD Connect for Exchange Hybrid. There, you are done and can manage your attributes with Exchange on Prem. You don’t need to build up any Hybrid connectivity, you are just using it for a management server. You will need to keep your Exchange server up to date though, so don’t forget to patch it.