Conference room declines when room is public and free

If the conference room is set to automatically accept meeting requests but is declining when added to a meeting invite, it could be due to how the room mailbox processes the invitation. One possible reason is that the room mailbox may treat the invitation as an external message if it is routed through a third-party mail service, which can prevent it from accepting the request automatically. This behavior is noted particularly in environments using a third-party mail service with mail flow connectors to route messages.

Additionally, if the room is configured to not accept recurring meetings or if there are specific settings in the room mailbox that restrict its availability, this could also lead to declines. You might want to check the room mailbox settings to ensure it is configured to accept requests appropriately.

To troubleshoot, verify the AutomateProcessing property of the room mailbox using the following PowerShell command:

Get-CalendarProcessing -Identity <name_of_room_mailbox> | select AutomateProcessing

Ensure it is set to AutoAccept.

If the issue persists, consider reviewing the booking policies and settings for the room mailbox to ensure they align with your expectations.

Dear @Jami Krch-Ellis,

Thank you for reaching out to Microsoft Q&A forum.

I understand you're experiencing an issue where a conference room accepts a booking when you schedule it directly from your calendar but declines it when added to a general meeting invite. From my research, this behavior strongly suggests a hidden permission or policy conflict within the room mailbox settings.

The core issue is that the room is differentiating between a direct, validated request (yours) and a broader, less-specific request (the general meeting invite).

The solution lies in reviewing the Calendar Processing settings for the room mailbox. Please forward these checks to your Exchange or Microsoft 365 administrator, as these require administrative access to resolve.

1. The Conflicting Organizer Issue

This is the most frequent cause in Microsoft Exchange/365 environments.

• The room mailbox is configured to only accept meetings booked by a specific user or group, or it's misinterpreting the general meeting invite. When you book it from your own calendar, you are the clear organizer, and the system works. When the room is added to a large meeting invite, the system might be confused about the actual owner or the identity making the booking request, especially if the invite originates from a delegate or a third-party app.
• An administrator needs to check the ProcessExternalMeetingMessages setting via PowerShell:  Get-CalendarProcessing -Identity "RoomName" | Format-List ProcessExternalMeetingMessages
• If this is set to False, the room will reject invites where the organizer's domain is deemed external or suspicious. It should usually be set to True for general acceptance.

For reference: Get-CalendarProcessing (ExchangePowerShell) | Microsoft Learn

2.Delegate or "In-Policy" Permissions

Your ability to book it directly suggests you have specific "In-Policy" rights that other organizers of the failed invite might lack.

• The room is configured to allow bookings only from "In-Policy" users (i.e., people within your organization or a specific group). If the original meeting organizer is from a different domain, tenant, or is a delegated user, the room may reject the request.
• The administrator should check the BookInPolicy and AllRequestInPolicy settings. If the user attempting to book the room is not specifically listed or part of the policy group, the room will decline.

For reference: Set-CalendarProcessing (ExchangePowerShell) | Microsoft Learn

Please ask your administrator to check the settings listed above, as the solution will almost certainly be found there. If you don't know who your IT administrator is, please refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support 

I hope this information is helpful. Please follow these steps and let me know if it works for you. If not, we can work together to resolve this. Thank you for your patience and understanding. If you have any questions or need further assistance, please feel free to share them in the comments so I can continue to support you. I'm looking forward to your reply.

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