Exchange 2013 decommission post migration to Office 365

pjmartins used Ask the Experts™
I want to decommission our Exchange 2013 platform which we have in Office 365 Azure AD sync environment, we had a DAG set-up and now down to single Exchange 2013, this is post cut over migration to Office 365 (we used CodwTwo), we want to neatly clean and remove Exchange 2013 without deleting users etc..  I can't find any real documentation for this, quite mixed opinions as some suggest to leave Exchange in existing cloud.

Is there a process to do this cleanly?  We have Azure AD Sync in place and all working 100%, just need to remove Exchange cleanly.

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I'm not familiar with CodeTwo, but if you performed a Cutover Migration to Exchange Online you wouldn't be syncing your on-prem AD unless you maybe configured Office 365 Azure AD Sync post-migration?  Can you clarify?
Regardless, if you're syncing AD I've always been on the opinion it is best to leave the last Exchange server on-prem so you can continue to manage mail attributes in AD (2010 but same concepts apply):

Most of the time the reason for most organizations that have configured a hybrid deployment, removing the last Exchange server from the on-premises environment will have adverse effects. In most cases, we recommend that you leave at least one Exchange 2010 Server on-premises for mailbox management unless you are getting rid of the on-premises messaging and identity management dependencies all together.
Todd NelsonSystems Engineer
Top Expert 2016
Here are a few references, directly from MS and MVPs.  The key to being able to remove Exchange from on premises is directory synchronization.  If you plan on keeping AAD Connect (which determines your source of authority as on premises), to remain supported you must keep at least one Exchange server on premises.

If you want to remove Exchange, 1) get rid of AAD Connect, 2) disable directory sync in O365, 3) remove Exchange, and then 4) get comfortable with managing identities in two locations.

P.S. In the MVA course, pay very close attention to the Hybrid Best Practices. Also, read all comments in the last reference.
Sandeep KumarAssociate Consultant
Refer to below discussions for Decommissioning Exchange Server post migration for 'to neatly clean and remove Exchange 2013 without deleting users' query.
PberSolutions Architect

No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I have recommended this question be closed as follows:

-- Jason Crawford (https:#a42418587)
-- Todd Nelson (https:#a42418859)
-- Sandeep Kumar (https:#a42421202)

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