Room Mailbox Calendar Permissions: Improving Meeting Visibility in Exchange Online

When managing room mailboxes in Exchange Online, you may find that the default calendar permissions are quite restrictive. By default, users can only view free/busy information for room mailboxes, which means they can see when a room is occupied but cannot view meeting titles, organizers, or other details. This limitation can make it challenging to manage room resources effectively and understand what meetings are taking place.

Note: This default calendar permission behavior applies to all mailbox types in Exchange Online - including User, Shared, Room, and Resource mailboxes. While this article specifically addresses room mailboxes, the same concepts and PowerShell commands can be applied to any type of mailbox to improve calendar visibility across your organization.

The Problem with Default Permissions

The default calendar permission for room mailboxes is set to AvailabilityOnly, which provides minimal visibility:

• Users can see if the room is busy or free
• No meeting titles are visible
• No organizer information is displayed
• No meeting details or locations are shown

This restricted view makes it difficult for administrators, facilities managers, or assistants to:

• Understand the purpose of meetings in rooms
• Coordinate room usage effectively
• Resolve scheduling conflicts
• Provide support for meeting organizers

That look like this:

Checking Current Calendar Permissions

Before making changes, it's important to verify the current permission settings for your room mailboxes. Use the following PowerShell command to check the existing permissions:

# Check permissions for a specific room mailbox
Get-MailboxFolderPermission -Identity "Meeting.Room1@bythepowerofgreyskull.com:\Calendar"

# Check permissions for all room mailboxes
Get-Mailbox -RecipientTypeDetails RoomMailbox | ForEach-Object {
    Write-Host "Room: $($_.DisplayName)" -ForegroundColor Green
    Get-MailboxFolderPermission -Identity "$($_.PrimarySmtpAddress):\Calendar" | Where-Object {$_.User -eq "Default"}
    Write-Host ""
}

The output will show the current AccessRights for the Default user, which typically appears as AvalibilityOnly for room mailboxes.

Setting Limited Details Permissions

To improve visibility while maintaining appropriate privacy, you can change the default permission to LimitedDetails. This permission level allows users to see:

• Meeting titles/subjects
• Meeting locations
• Time slots (busy/free status)
• Basic meeting information

For a Single Room Mailbox

# Set Limited Details permission for a specific room
Set-MailboxFolderPermission -Identity "Meeting.Room1@bythepowerofgreyskull.com:\Calendar" -User Default -AccessRights LimitedDetails

For All Room Mailboxes

# Get all room mailboxes and set Limited Details permission
Get-Mailbox -RecipientTypeDetails RoomMailbox | ForEach-Object {
    Set-MailboxFolderPermission -Identity "$($_.PrimarySmtpAddress):\Calendar" -User Default -AccessRights LimitedDetails
    Write-Host "Updated permissions for $($_.DisplayName)" -ForegroundColor Green
}

Verifying the Changes

After applying the permission changes, verify that they have been implemented correctly:

# Verify changes for a specific room
Get-MailboxFolderPermission -Identity "Meeting.Room1@bythepowerofgreyskull.com" | Where-Object {$_.User -eq "Default"}

# Verify changes for all room mailboxes
Get-Mailbox -RecipientTypeDetails RoomMailbox | ForEach-Object {
    $permissions = Get-MailboxFolderPermission -Identity "$($_.PrimarySmtpAddress):\Calendar" | Where-Object {$_.User -eq "Default"}
    Write-Host "$($_.DisplayName): $($permissions.AccessRights)" -ForegroundColor $(if($permissions.AccessRights -eq "LimitedDetails"){"Green"}else{"Red"})
}

Permission Levels Reference

Here are the available permission levels for calendar folders:

• None: No access to the calendar
• AvailabilityOnly: View free/busy information only (default for room mailboxes)
• LimitedDetails: View free/busy, subject, and location
• Reviewer: Read items in the calendar
• Contributor: Create items but cannot view other items
• Author: Create and read items, modify and delete own items
• Editor: Create, read, edit, and delete all items
• Owner: Full control of the calendar

Conclusion

Changing room mailbox calendar permissions from the default AvailabilityOnly to LimitedDetails significantly improves visibility into room usage while maintaining reasonable privacy boundaries. This change helps administrators and support staff better manage room resources and assist users with meeting-related issues.

Remember to test these changes in a controlled environment first and communicate the changes to your users, as they will now see more information about room bookings than they could previously.