The strategies in this post help you to solve the ExchangeGUID does not correctly update issue.
I had a bad day because of the user account licensed with Exchange Online Plan 2 but no mailbox in cloud and on-premise has remote user mailbox.
I updated the ExchangeGUID of the affected mailbox into null (00000000-0000-0000-0000-000000000000) in order to visible the mailbox in cloud.
Sadly, the steps didn’t work and the ExchangeGUID in on-premise kept changing automatically. Here’s the screenshot for better understanding.

As you can see the ExchangeGUID appears different initially so I updated into null but it got immediately changed to something else without manual effort. I waited for 24 hours but no luck.
Finally, I decided to try the ADAC (Active Directory Administrative Center) 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“
- Select “Clear“

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

I waited for sync and removed the Exchange Online Plan 2 license and added it back. Guess what? Exchange GUID does not correctly update issue has 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:
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