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I have an on-prem AD but have Office 365/Azure/Entra and now I can not go into MS admin and hide from the address list. when I turn on the toggle I get "Could't update mailbox global address list info" See the screenshot below
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Hello, @Debbie Drummond
It's been a long time since I've heard from you, have you solved your problem yet? Did my previous reply help you？ If it was useful, you can mark it as an answer. Thank you for your understanding and support.
Just checking in to see if the below answer helped. If this answers your query, please don’t forget to click "Accept Answer" which might be beneficial to other community members reading this thread. And, if you have any further query do let us know.
If you are syncing from on-prem, then you need to hide the mailbox on-prem via the on Exch Mgmt tools and that will sync to Azure.
Andy even if my Exch is not on prem? My Exchange is online.
Andy My Exch is online not on prem. Thought I would only do this if Exch server was on prem
Did you migrate mailboxes from on-prem? Are you syncing Exch Atttributes and ad Accounts from on-prem?
If so, then you would need to manage the Exch attributes on-prem as well.
We did migrate about two years ago but we just started the Cloud Sync. We had not had our Office 365 sync with AD until about 2 months ago. We rolled out Defender/Azure(Entra) Intune. I had an outside consultant do it and just now found it not working. They said that I would have to go in and do a manual hide for each one I wanted to put in the hide list. knew this worked before we went to cloud sync and thought there should be a better way to manage this.
Hi，@Debbie Drummond
Thanks for posting your question in the Microsoft Q&A forum.
According to your description, this problem occurred after migrating the on-pre mailbox to Online.
Reason：
On-premises is the source of truth for users, they cannot be edited directly in O365.
Solution：
As Andy said, you need to manage the Exch attributes on-prem as well to complete the modification.
You also extend your on-premises AD schema with the Exchange attributes, then you will be able to make the changes. Alternatively, you can disable dirsync, make the changes, re-enable it.
If my answer is helpful to you, please mark it as the answer so that other users can refer to it. Thank you for your support and understanding.