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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 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 the issue and wanted to share the strategies that I followed in this post.

This user's on-premises mailbox hasn't been migrated to Exchange Online
  • Go to “Exchange On-Premise
  • Access the “Exchange Management Shell
  • Disable the affected mailbox.
    Note: I strongly advise not to use remove-mailbox as they remove the AD account that is associated with a mailbox. I recommend using the disable command.
microsoft office 365
  • Waited for the changes to replicate. After sync, the account had no mailbox in the cloud but they listed in the soft-deleted.
  • Enable the on-premise object again using Enable-Mailbox command.
    Note: If no AD account is available, the Enable-mailbox command will not work.
office 365 mailbox
  • After the sync is completed, initiate migration to Exchange Online from on-premise and assign a respective license.
  • The mailbox appears to be ok and no more error (This user’s on-premises mailbox hasn’t been migrated to Exchange Online).
outlook office 365
  • Now, perform the mailbox restore request to move contents from the soft-deleted mailbox to the active mailbox.
  • Finally, add the proxy addresses of a soft-deleted mailbox to the active mailbox to make sure all emails receive to the active mailbox.

If the above steps fail, follow the instructions mentioned in 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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