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[SOLVED] Office 365 Mailbox Does Not Exist

Today I’m going to show you on how to solve office 365 mailbox does not exist issue.

I had a painful day where in a user associated with a remote user mailbox in on-premises but no mailbox is provisioned in Microsoft 365 but exchange online license is assigned. The strategies in this post help you to solve the issue.

Let’s jump right in.

In this case, the Exchange GUID needs to be updated in on-premises because it’s a hybrid environment with Azure AD Connect to sync objects.

To update the attribute, follow the below steps.

  • Launch “Exchange On-Premises PowerShell
  • Update the Exchange GUID to null to the affected mailbox.
    For example, Set-RemoteMailbox test2222 -ExchangeGuid 00000000-0000-0000-0000-000000000000

For more information about the Remote Mailbox, visit the Microsoft website.

Office 365 mailbox does not exist
  • Make sure the ExchangeGUID reflects correctly in on-premises. If it is incorrectly set for some reason, follow the steps mentioned in this article.
Office 365 mailbox does not exist
  • Wait for the changes to reflect to cloud. The object in Microsoft 365 should reflect the changes applied in on-premises.
microsoft office 365
  • As you can see, the changes synced to Microsoft 365. The next step is to remove the Exchange online license and wait for 15 minutes and re-add the license again and see how it goes.
mailbox does not exist

Woohoo!!. The object in cloud shows as a user mailbox. The office 365 mailbox does not exist issue is fixed.

Also Read: How To Solve Shared Mailbox Showing As Mail User?

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

Now I’d like to hear from you:

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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  2. Cicindela

    Hi, thank you this work well, i got MailboxOnline but ExchangeGUID is different between remotemailbox ( 00000000-0000-0000-0000-000000000000) and onlineMailbox ( New ExchangeGUID). Is it a problem ?

    • techieberry

      Tested the behavior in a hybrid environment and the mailbox is not being deleted. It is also showing a mailbox in Exchange online.

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