When you plan to move from on-premises Exchange Server to Exchange Online, then you have two scenarios in front of you. Either you want to keep both the Exchanges at the hybrid environment, or you want to uninstall the on-premises Exchange Server. The hybrid environment is the only arrangement where you can quickly onboard and off-board the Exchange mailboxes. All other environments use onboard mailboxes only. There are following features which are only available at the hybrid Exchange Server –

  • Cross-premises availability: It presents you with the user’s busy/free status while you plan a meeting.
  • Cross-premises archive: It allows you to migrate only the user’s archive mailboxes rather than the primary mailbox or the public folder. Only the archive mailbox will go to the Office 365 or Exchange Online.
  • Cross-premises discovery searches: It allows the user to run an e-discovery search in both the platforms (on-premises and Office 365.)
  • Outlook Web App URL redirection: It redirects the URL to the useful Outlook Web app access.
  • No profile recreation after moving: At the hybrid platform, you do not need to create a new profile at the Office 365 platform, but you can access the same profiles with their previous credentials.

The disadvantage of decommissioning the on-premises Exchange Server

Many times, when all the mailboxes have migrated from on-premises Exchange to Exchange Online, then the user decides to move on from the Exchange Server permanently. But, when they decommission the Exchange Server, then they are unable to access the mailboxes at the Office 365 because the directory synchronization.

Although if you have worked in the hybrid environment for a more extended period and now want to move to the cloud entirely, then you need to follow a lengthy procedure of removing the settings and connection from Exchange Server before uninstalling it.

Decommission on-premises Exchange Server

When you are working in a hybrid configuration where all the mailboxes are in Exchange Online and not using the on-premises Exchange Server, then you can disable the directory synchronization and later uninstall the Exchange Server provided there is no directory synchronization. This is how you can remove directory synchronization:

  1. Run the command to check if the public folder is set as ‘Remote.’
    Get-OrganizationConfig | Format-List PublicFoldersEnabled

    If the public folder is set at remote, then you need to migrate the Public folder to the Exchange Online.

  2. When all the mailboxes are in Exchange Online, then point the MX and Autodiscover DNS records to Exchange Online.
  3. Remove the Service Connection Point (SCP) values from the Exchange Server.
    Get-ClientAccessServer | Set-ClientAccessServer -AutoDiscoverServiceInternalUri $Null
  4. Remove the inbound and outbound connectors from the Office 365 admin portal which is created by Hybrid Configuration Wizard.
    • Log in to Office 365 Admin portal using the Administrator credentials.
    • Go to mail flow, and then connection. Here, select the inbound and outbound connector and disable it.
  5. Remove the organization relationship from the Office 365 Admin Center created by the Hybrid Configuration Wizard.
    • Log in to Office 365 Admin portal using the Administrator credentials.
    • Go to Organization, then select sharing. Here, select the value and delete it.
  6. Now, disable the directory synchronization to all the users. After completing this step, all the management task of Office 365 can be completed through the Office 365 Admin Center. Now you do not need the Exchange Admin Center (EAC) or Exchange Management Console for managing the mailboxes.
  7. Uninstall the on-premises Exchange Server from the environment.


Decommission the Exchange Server in the hybrid environment is the final step after successful completion. The whole process to select the source data from Exchange Server and migrate it to Exchange Online is a lengthy process if you run it manually. If you want to gain more control of the migration process, you should use Exchange Migration software. It will automate all the migration processes and provide you an ample time to continue to work on the data. Later, you can decommission the Exchange Server using the method mentioned above.