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[SOLVED] This User’s On-premises Mailbox Hasn’t Been Migrated To Exchange Online In Microsoft 365

I received the strange issue in a Hybrid environment where in a user account received the error that this user’s on-premises mailbox hasn’t been migrated to Exchange Online. I was able to fix it and wanted to share the strategies in this post.

This user's on-premises mailbox hasn't been migrated to Exchange Online
  • Go to “Exchange On-Premises”
  • Access the “Exchange Management Shell
  • Disable the affected mailbox. For example, Disable-RemoteMailbox Test248 -Confirm:$false
    Note: I strongly advise not to use the remove-mailbox as it removes the AD account that is associated with the mailbox. I recommend to use the disable command.
microsoft office 365
  • Wait for the changes to replicate in Microsoft 365. After the sync, the mailbox will be moved to the soft deleted list.
  • Now, enable the on-premises object again using the Enable-Mailbox command and not remote user mailbox. For instance, Enable-Mailbox test248
    Note: If there is no AD account available, then Enable-mailbox command will not work.
office 365 mailbox
  • After the sync is complete, perform the migration from on-premises to Exchange Online and assign the license.
  • The mailbox should be ok now. This has been tested in my lab and the error (This user’s on-premises mailbox hasn’t been migrated to Exchange Online) no longer occurs.
outlook office 365
  • Now, perform the mailbox restore request to move mailbox contents from the soft-deleted mailbox to the active mailbox.
  • Finally, add the email addresses of the soft-deleted mailbox to the active mailbox to receive all emails to the current mailbox.

If the above steps fail for some reason, follow the instructions mentioned in the Microsoft website.

Want to improve your Exchange Online experience for better productivity? Check out the tips and tricks mentioned here.

Did I miss anything? Or maybe you have a question about something that I covered.

Either way, I’d like to hear from you. So go ahead and leave a comment below.

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