Exchange 2010 decommission in Hybrid Environment

Daniele Zelli
Daniele Zelli used Ask the Experts™
Hi guys,
I have only one Exchange Server 2010 on premises: Version 14.3 (Build 123.4) with the folowing roles installed: Hub Transport, Client Access, Mailbox in Hybrid Environment with Office 365.
I use Microsoft Azure AD Connect 1,1,751.0 for AD syncronization with the Cloud.
I have migrated all the mailboxes an I would like to get rid of the on-premises Exchange Server.

I have read many articles on this and everyone approach the decommissioning in a different way, most articles I have found also suggest to keep the on premises Exchange.
After having modified the public DNS records to point to the cloud (MX, autodiscover...etc..) and moved all the mailboxes to the cloud  what are the steps for a clean decommission of the on premises Exchange?
I assume that I should somehow modify the AD schema to "clean" the unwanted Exchange attributes right?
If yes, how?
I assume I should keep  Microsoft Azure AD Connect to syncronize passwords and AD attributes, right?

As you guys can see I'm quite confused, hope someone could spare some recommendation for me to go through the process

Thanks a lot
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Most Valuable Expert 2015
Distinguished Expert 2018

No, you should not "clean" any attributes, you can convert the mailboxes to mail users if that's what you mean. Whether you should keep AAD Connect is up to you, but if you decide to keep it, this means that you need to keep at least one Exchange box for management purposes, if you want to stay in supported configuration. The reason for that is that using AAD Connect means you will be managing objects and their attributes from on-premises, and the only supported tools to manage Exchange related attributes are the Exchange tools. Keyword here is "supported" - you can just as easily manage them via ADUC or PowerShell or any other tools you might use, however Microsoft does not support such configuration and if you run into any issues, you are on your own.

There are more details about this here:
MASEE Solution Guide - Technical Dept Head
Most Valuable Expert 2017

Agree Vasil. Adding to the above you dont need an Exchange license to manage your O365 users.
Managing Consultant
To follow on, I strongly suggest that you keep an on-premises Exchange server. Doing the attribute changes manually is painful. Further, migrate that server from Exchange 2010 to Exchange 2016. The on-premises Exchange server in a hybrid environment can be small - it doesn't need the "power and size" of an on-premises server that is hosting mailboxes.

Also you should seriously consider updating your Azure AD Connect to the current version. There are known issues with the version you are running.
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Daniele ZelliSystems Engineer


Thanks a lot for your answers guys, I guess I won't get rid of the Exchange Server then.

Summarizing this is what I will need to do:

  • Migrate Exchange from 2010 to 2016 on-premises
  • Upgrade Azure AD Connect to the latest version

The questions are:
Do I need a license for Exchange 2016?
What role should be installed in the new Exchange 2016?

Also, now that you guys have pointed me in the right direction I'm researching for articles, if you guys have any suggestion will be much appreciated :)
Michael B. SmithManaging Consultant

If the only reason you have Exchange 2016 on-premises is to manage mailboxes in Office 365, you do not need a license for the server, or for client access.

In Exchange 2016 there is only one role: Mailbox (well, there is also Edge and ManagementTools, but you should ignore those). :-)
Daniele ZelliSystems Engineer


Thanks Michael, the current Hybryd environment relies on the Exchange 2010 for client access, the MX record and the autodiscover are pointing to the on premises environment, should this change to the cloud once I have migrated to Exchnage 2016?
Michael B. SmithManaging Consultant

Yes. In fact, if you have moved all mailboxes to the cloud already, you can change MX and autodiscover to O365 now.

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