The strategies in this post will help you solve the ExchangeGUID does not correctly update issue.
I had a bad day where the user account was licensed with Exchange Online Plan 2 and no mailbox was provisioned in cloud but the user had a remote user mailbox in on-premises.
To resolve the issue, I updated the ExchangeGUID of the affected mailbox in on-premises to null (00000000-0000-0000-0000-000000000000) to see how it works. Sadly, the steps didn’t work for some reason. The ExchangeGUID in on-premises keeps changing on its own. Take a look at the screenshot for a better understanding.

As you can see, the ExchangeGUID appeared different initially so I updated it to null but the changes did not update without my action. I tried the same steps after 24 hours but with no luck. Finally, I decided to try the Active Directory Administrative Center (ADAC) to update them.
- Go to “Active Directory Administrative Center“.
- Select “Global Search“.
- Search the affected user account.
- Click “Properties” on the right.

- Select “Extensions” on the left.
- Select “Attribute Editor“.

- Select “msExchMailboxGuid“.
- Click “Clear“.

Once this is done, check the status in via Powershell to make sure this is working.

Let’s wait for a few hours for these changes to reflect in cloud. Once it is synced, remove the Exchange Online Plan 2 license and wait 15 minutes and add it back. Guess what? The Exchange GUID does not correctly update issue has been resolved. Woohoo!!
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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