how to stop double bookings in room resources

To stop double bookings in room resources in Exchange, you need to ensure that the room mailbox is configured to automatically decline conflicting meeting requests. This can be achieved by setting the AllRequestOutOfPolicy property of the room mailbox to False. When this property is set to True, the room mailbox ignores conflicting meeting requests, allowing double bookings to occur.

Here are the steps to resolve this issue:

1. Connect to Exchange Online using remote PowerShell.
2. Run the following command:

      Get-CalendarProcessing -Identity "Meeting Room" | Set-CalendarProcessing -AllRequestOutOfPolicy $False
   

This configuration will ensure that if a room is already booked, any subsequent booking requests that conflict with the existing reservation will be automatically declined.

Additionally, you can also configure the room mailbox settings to allow or prevent conflicting meeting requests through the resource scheduling options in Outlook on the web.

References:

• Microsoft 365 users can reserve a meeting room even though it's already reserved for another meeting
• Change how a room mailbox handles meeting requests

Hi @Ross Baxter

Thank you for posting your question in Microsoft Q&A. 

Based on my research, this issue is typically caused by misconfigured calendar processing settings on the room's resource mailbox.  By default, room mailboxes are designed to automatically accept valid bookings and decline conflicting ones. However, if settings such as AllowConflicts or AllRequestOutOfPolicy are enabled, they may allow overlapping bookings. 

To resolve this, you can follow these steps to verify and configure the settings using PowerShell: 

Connect to Exchange Online PowerShell 

To verify the resource mailbox configuration, run:

Get-CalendarProcessing -Identity "******@yourdomain.com" | FL AllowConflicts, AllRequestOutOfPolicy, AutomateProcessing 

It should display: AllowConflicts: False, AllRequestOutOfPolicy: False, AutomateProcessing: AutoAccept. 

If not, you can run the following command to reconfigure the settings:

Set-CalendarProcessing -Identity "******@yourdomain.com" -AllowConflicts $false -AllRequestOutOfPolicy $false 

Test the configuration by creating test bookings to ensure conflicts are properly declined. 

Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. 

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