We have a small-organization, on-premises Exchange 2010 setup running on Server 2008 R2. Our goal is to migrate to Exchange 2016 running on Server 2016 (I guess -- I would prefer Server 2019, but apparently that is not supported for Exchange 2016.)

We do not have a test domain set up, which is probably part of the problem, but which is probably not going to be fixed.

I have been reading through the Exchange Assistant , Microsoft documentation) and answers here (eg Migrate from Exchange 2010 to Exchange 2016). I am getting a grasp of the basics, but I am confused about how to install Exchange 2016 without it taking over functionality from Exchange 2010 right away.

I would like to install Exchange 2016 in my environment, but have all my users continue to use Exchange 2010 for their Outlook and OWA setups. Then I would like to change configuration to start using Exchange 2016 functionality later. But from what I have read about coexistence, it appears that Exchange 2016 becomes the default connection point immediately (eg, as described in this coexistence document ).

My questions:

  • Is it the case that Exchange 2016 will begin serving my existing clients as soon as I install it?

  • If so, is there a way to stop this? Part of this looks like changing the Service Connection Point published in Active Directory using the Set-ClientAccessService cmdlet, as documented in step 6 here. It looks as if I also have to unset (or refrain from setting) DNS entries for autodiscover. Is there more?

  • Related to the above: are there ways to revert whatever changes Exchange 2016 will make so that I can use Exchange 2010 exclusively again?

  • At what installation/migration step do I lose the ability to back out of the migration and go back to Exchange 2010? Is it as soon as I successfully install the product? Earlier? Later? I was reading that doing the schema updates prohibits me from installing a new Exchange 2013 server (but I still think I can install an Exchange 2010 one).

Thanks for any insight you can offer, and apologies if these are dumb questions.


If you set up a separate Exchange 2016 environment next to your existing Exchange 2010 one, at first nothing at all should happen. The reference in point 6 you mention seems to be a precaution to ensure it stays that way initially.

When you're confident enough that you have a working configuration on the Exchange 2016 environment and that it can interact with the Exchange 2010 server(s), you may configure your DNS records - one service at a time - to point at the new machines.

All this time, if anything goes wrong, simply point the DNS records back to your old server.

During this transition period, the new Exchange version will proxy requests back to the older environment when necessary - for example when delivering mail.

Then you will migrate mailboxes to the new server(s), and finally - after you've confirmed that everything relevant is still working - clean up your environment to rid it of references to the old mail servers, and remove them.


Agree with Mikael H, If you only install exchange 2016, it will not affect the existing exchange 2010.

You say go back to exchange 2010, yes, you can, If all mailboxes are on exchange 2010 and there are no mailboxes on 2016. If there is a mailbox on exchange 2016, and all urls point to exchange 2010, the mailbox on exchange 2016 will no longer be available.

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