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Roll back a public folder migration from Exchange Server to Exchange Online

If you run into issues with your public folder migration to Exchange Online, or for any other reason need to reactivate your Exchange Server public folders, perform the following steps:

Roll back the migration

If you roll back your migration, you will lose any content that was added to public folders in Exchange Online post-migration, either through clients or via email for mail-enabled public folders. To save this content, you can export the post-migration public folder content to a .pst file, which can then be imported into the on-premises public folders when the rollback is complete.

  1. In your Exchange on-premises environment, run the following command to unlock your Exchange Server public folders:

    Set-OrganizationConfig -PublicFolderMailboxesLockedForNewConnections:$false -PublicFolderMailboxesMigrationComplete:$false -PublicFoldersEnabled Local


    The unlocking may take several hours.

  2. In your Exchange on-premises environment, revert the ExternalEmailAddress of any mail-enabled public folder that was updated by SetMailPublicFolderExternalAddress.ps1 (the script used in Step 8: Test and unlock public folders in Exchange Online of Use batch migration to migrate Exchange Server public folders to Exchange Online). You can refer to the summary file created by the script to identify the ones that were modified, or use the OnPrem_MEPF.xml file generated earlier in the same batch migration process to get the original properties for all mail-enabled public folders.

  3. In Exchange Online PowerShell, run the following commands to remove all Exchange Online public folders and mailboxes:

    Get-MailPublicFolder -ResultSize Unlimited | where {$_.EntryId -ne $null}| Disable-MailPublicFolder -Confirm:$false
    Get-PublicFolder -GetChildren \ -ResultSize Unlimited | Remove-PublicFolder -Recurse -Confirm:$false
    $hierarchyMailboxGuid = $(Get-OrganizationConfig).RootPublicFolderMailbox.HierarchyMailboxGuid
    Get-Mailbox -PublicFolder | Where-Object {$_.ExchangeGuid -ne $hierarchyMailboxGuid} | Remove-Mailbox -PublicFolder -Confirm:$false -Force
    Get-Mailbox -PublicFolder | Where-Object {$_.ExchangeGuid -eq $hierarchyMailboxGuid} | Remove-Mailbox -PublicFolder -Confirm:$false -Force
    Get-Mailbox -PublicFolder -SoftDeletedMailbox | Remove-Mailbox -PublicFolder -PermanentlyDelete:$true -Force
  4. Run the following command in your Exchange Online environment to redirect public folder traffic back to on-premises (Exchange Server):

    Set-OrganizationConfig -PublicFoldersEnabled Remote
  5. See Configure Exchange 2013 public folders for a hybrid deployment for instructions on reconfiguring access to your on-premises public folders, so that your Exchange Online users can access them.