Calendar Problems

How to Remove a Ghost or Duplicate Room Mailbox in Microsoft 365

Maira Mehtab Sep 22, 2026 869 views

Question details

Users need to completely remove a deleted and recreated room mailbox that is still showing up as a duplicate entry in search results.

Product: Microsoft 365 / Exchange Online
Device & OS: not provided
Scenario: Searching for a room mailbox to book a meeting in Microsoft 365 or Outlook.
Observed behavior: A deleted room mailbox continues to appear as a duplicate or 'ghost' entry in search results across multiple browsers and users, despite not being visible in the Microsoft 365 portal.

Before you start

Ensure you have Exchange Administrator privileges in your Microsoft 365 tenant and that you have the Exchange Online PowerShell module installed on your computer.

Solution 1Recommended

Identify and Remove Hidden or Soft-Deleted Mailboxes via PowerShell

Use Exchange Online PowerShell to detect mailboxes that are hidden from the address list or lingering in a soft-deleted state on the server.

When a mailbox is deleted and recreated, the old entry may remain in a soft-deleted state or become hidden, causing the global address list to return duplicate results.

Check for hidden room mailboxes

Open PowerShell, connect to Exchange Online, and execute: Get-Mailbox -RecipientTypeDetails RoomMailbox -ResultSize Unlimited | Where-Object {$_.HiddenFromAddressListsEnabled -eq $true}

Check for soft-deleted mailboxes

Run the command: Get-Mailbox -SoftDeletedMailbox to see if the previous instance of the room mailbox is still retained by Exchange.

Remove the identified duplicates

Once the ghost entry's identity or GUID is found, use the Remove-Mailbox command to permanently purge the lingering mailbox from the system.

Microsoft Support: If you are unable to clear a soft-deleted mailbox due to retention holds, you may need to reach out to Microsoft Support to force the deletion.

Solution 2

Clear the Auto-Complete List in Outlook

Clear local cache to ensure the duplicate entry isn't simply being recalled by the email client's memory.

Solution 3

Force an Active Directory Synchronization

If your environment uses hybrid directory synchronization, manually force a delta sync to push the removal of the old mailbox to Microsoft 365.

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Frequently Asked Questions

Why do deleted room mailboxes still appear in Outlook search?

This usually happens because Outlook relies on a locally cached Offline Address Book (OAB) or the Auto-Complete list. It can take up to 24-48 hours for address book changes to synchronize fully across all clients, or you may need to clear the local cache.

What is a soft-deleted mailbox in Microsoft 365?

When you delete a mailbox in Microsoft 365, it is moved to a 'soft-deleted' state for 30 days by default. During this period, the mailbox can be recovered. However, its lingering presence can sometimes cause duplicate search results.

How long does it take for a manual AD sync to reflect in Microsoft 365?

After running a delta sync using AD Connect, the changes typically appear in the Microsoft 365 admin center within a few minutes. However, propagation to the Exchange global address list and end-user Outlook clients may take longer.

Outlook & Email Problems