Do you still need the Exchange server after completing the Office 365 migration?

Fernando Marambio
Fernando Marambio used Ask the Experts™
Hi all,

We are coming from Office 365 Hybrid migration, and while having a small chat with MS support the other day, it was casually mentioned that I would still have to use the old Exchange server even after retiring that server after completing the migration.  The guy said that I would have to use Exchange for advance commands which are not found on the Office 365 portal.  Is this scenario true or can we rely on the Office 365 portal 100% and completely sunset the onle Exchange 2010 server?
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Exchange Engineer
Distinguished Expert 2018
This is a good question and it seems that is correct, but there are a few caveats, but this will depend on your setup and environment. The below article is excellent in explaining this issue.
Todd NelsonSystems Engineer
Top Expert 2016
Like Andy stated, it is dependent on directory synchronization.

If you do not have directory synchronization installed (i.e. AAD Connect) and are not syncing AD objects to O365, then you can remove Exchange and still be supported by Microsoft.

However, if you have directory synchronization installed and remove Exchange, then MS states you are no longer in a supported configuration.  IMO, MS is trying to prevent admins from doing stupid things that could potentially affect AD in general.

If you are thinking about removing Exchange, consider reducing the footprint of Exchange--like number of servers, amount of memory, number of CPUs, size of storage; which is relatively easy to do if the server is virtualized--and maintain Exchange for management purposes only.
timgreen7077Exchange Engineer
Distinguished Expert 2018

Answer provided to author. Closing question unless author reopens.

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