research Question

Cutover v. Hybrid Exchange migration

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Hypercat (Deb)Flag for United States of America asked on
ExchangeMicrosoft 365Active DirectoryAzure
7 Comments3 Solutions9 ViewsLast Modified:
I'm preparing to do a migration from an on-prem Exchange 2019 server to Microsoft 365.  I've read a number of articles regarding how to do both a Hybrid and Cutover migration.  The firm has only 20 mailboxes but between active and archive mail databases, there is about 600GB of email to be migrated.  I would prefer to do a Hybrid migration because it seems less disruptive to the users.  

HOWEVER, I want to end up in a situation where there is no on-premises Exchange server, so I'll be uninstalling Exchange from the on-premises server at the end of the process.  The articles I'm reading insist that if you're using "directory synchronization" then you have to leave the on-prem server up and running.  I'm completely stymied by this reasoning.  We already have a Microsoft 365 tenant set up for the firm with Azure AD synch running.  It's working perfectly fine. All the user accounts are synched and they've all been licensed for Office 365.

So, my question is: Are they referring to a different "directory synchronization" method (i.e., ADFS) that requires Exchange to be running?  If not, how would doing a Hybrid migration and then uninstalling the on-prem Exchange server break or cause issues with Azure AD?

Saif Shaikh
Server engineer

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