Remove local Exchange mailbox but retain AD User and Exchange attributes as Azue AD Connect is in place

Ryan E 1 Reputation point

I have a customer that migrated from a local Exchange 2013 server to Exchange Online using Bittitan. They also have Azure AD Connect in place syncing local AD users to Microsoft 365. They are all currently using Exchange Online, and the local Exchange Server is no longer being used but all of the old mailboxes that were on the local Exchange server are still there.

We would now like to remove the local Exchange mailboxes, and then remove the Exchange 2013 server and simply retain a new Exchange 2019 server for user management. I know that I can disable a mailbox to remove the mailbox and retain the user's AD account. However, when you do that, you also remove the Exchange attributes included the AD account. Then when it syncs to M365/Azure AD, it will remove the email address on the account.

What is the best way to remove these mailboxes while keeping AAD Connect?


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  1. JimmySalian-2011 42,066 Reputation points


    This is a complex requirements and I will try to redirect you to couple of MS Articles and please review the scenarios listed it should assist you. Also AFAIK when you remove last exchange server it should not remove any attributes unless there is some misconfiguration in the enviroment or some dependency with the user objects? However I can say you can safely do that task and also take /export attributes of the user objects and continue using AAD Connect and new Exchange 2019.

    Check Scneraio 2 in the link.

    Hope this helps.

    Please Accept the answer if the information helped you. This will help us and others in the community as well.