Getting a ValidationException when permanently deleting a soft-deleted mailbox

Question

Why Im getting ValidationException when permanently deleting a soft-deleted mailbox synced from Exchange 2019. The LitigationHoldEnabled flag is stuck on True, but the on-prem AD object is already deleted, so I can’t disable it via sync.

Answer 1

Hi Nurhaziq Adi

As far as I know, the ValidationException happens because the mailbox is still treated as being under a hold state. A hold is designed to preserve mailbox content for compliance/legal purposes until the hold is removed, so deletion workflows can be restricted while that hold state remains.

In hybrid scenarios, if the mailbox was originally synchronized from Exchange Server 2019 and the on‑premises AD object has already been deleted, it can leave the cloud mailbox in a “soft-deleted but held” condition where the hold can’t be cleanly managed through the original directory object.

Technically, you can try the below approach to see if it can help you:

• Confirm the mailbox is in the expected deletion state (inactive vs soft-deleted) and review hold-related settings.
• If any holds can be removed through normal administrative controls, remove them first, because holds are intended to preserve content until they are cleared.

Hope my answer will help you

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".   

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

The ValidationException occurs because Exchange Online blocks permanent deletion of a mailbox that is still on hold (LitigationHoldEnabled = True). A mailbox under any hold state cannot be hard-deleted until the hold is removed.

In this scenario:

• The mailbox is soft-deleted in Exchange Online.
• The associated on-premises AD object (and thus the on-premises mailbox) has already been deleted, so the Litigation Hold state cannot be changed via directory sync.
• Because the mailbox is still on hold, Exchange Online validation prevents using Remove-Mailbox -PermanentlyDelete or equivalent hard-delete operations, which results in the ValidationException.

Key points from the data deletion model:

• A hard-deleted mailbox (permanently removed) is only possible when the mailbox is not in any hold state such as Litigation Hold or eDiscovery hold.
• One of the documented hard-delete paths is: “You delete a soft-deleted mailbox by using Remove-Mailbox -PermanentlyDelete,” but this explicitly assumes the mailbox is not on hold.

So the root cause of the ValidationException is the active Litigation Hold on the soft-deleted mailbox. As long as LitigationHoldEnabled remains True, Exchange Online will not allow permanent deletion.

---

References:

• Microsoft 365 Exchange data deletion
• Delete or restore user mailboxes in Exchange Online
• Disconnected mailboxes in Exchange Server
• Permanently delete a mailbox in Exchange Server