Exchange 2016 to Online migration

[MSCom]

Hello everyone,


for one of our clients we manage an Exchange 2016 Server with about 50 Mailboxes.
Since users access their mails from different offices and we don't see any benefits keeping the exchange server, we would like to shut it down after moving all mailboxes to Exchange Online.
O365 with DirSync is already in use for managing Office licenses.


Since we don't want any downtime, cutover-migration is not really an option for us.
After reading the main articles about Exchange Server to Exchange Online migration I still couldn't find out, if I may use DirSync AND shut down the Exchange Server AND still be supported by Microsoft.

My idea:
- 1. Minimal-Hybrid migrate everything to exchange online (which should be very simple)

- 2. Disable AD Connect (passwords should stay as they are, I assume)

• 3. Uninstall Exchange Server (and go 100% Cloud)
• 4. Now activate DirSync again in order to manage existing and new users via AD and Office 365 Admin Center

After disabling AD Connect I am allowed to manage everything in O365 Admin Center and shut down the Exchange Server, right?
So I don't understand why I do need an Exchange Server for management. (I know, there are free licences for this usecase, but my boss ...)
Maybe there is a Powershell-Script to remove every hint to a gone hybrid constellation, which I didn't find.

What is the difference between

• my Office 365 tenant after step 3 (hybrid migration, disabled AAD Connect, no more Exchange Server) and
• an Office 365 tenant that has never been in a hybrid constellation?

So all in a nutshell:
May I somehow

• shutdown the Exchange Server
• still (or again) sync passwords and users with AD
• stay supported?

Thank you for your help

Greetings
Alex