The room list behavior that we see  in Outlook is by design. When we  use a Room List  for a meeting, it is stored in the  Most Recently Used entries in the registry. When we create a new meeting, we will see this MRU entry in the top of the Room Lists . The same Room List will be seen again in the drop down which is accessed from the Exchange Server/ Online.

To prevent the duplicate entries seen in the Room List, create the below registry entry with blank data to disable the  Most Recently Used  Room List in Outlook.

Path: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\Preferences

Key: RoomFinderRecentRooms
Key: RoomFinderRecentRoomList

If these entry already exist just empty the values.

After Outlook Restart:

 Only single instance of the rooms list now showing!

In simple terms Room List work  as distribution groups for conference or other types of rooms.

Use PowerShell to login to Office365:

#Connect to Office365
Import-Module MSOnline
$O365Cred = Get-Credential
$O365Session = New-PSSession –ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell -Credential $O365Cred -Authentication Basic -AllowRedirection
Import-PSSession $O365Session

Create a room list:

New-DistributionGroup -Name HQ -DisplayName "HQ" –PrimarySmtpAddress [email protected] –RoomList

Add rooms to a list:

Add-DistributionGroupMember –Identity "HQ" -Member [email protected]

Check what Room Lists you have:

Get-DistributionGroup | Where {$_.RecipientTypeDetails -eq "RoomList"} | Format-Table DisplayName,Identity,PrimarySmtpAddress

Check what conference rooms are part of a particular room list:

Get-DistributionGroupMember –Identity "HQ"

I like to make resource booking days 1 year from the day of making the reservation/ appointment. Now instead of visiting each calendar and making the change, powershell can help us out.

#Connect to Office365 
$cred = Get-Credential
Import-Module MSOnline
Connect-MsolService -Credential $cred
$s = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell -Credential $cred -Authentication Basic -AllowRedirection
$importresults = Import-PSSession $s

#Get all the Rooms and make the booking days to 365
Get-MailBox | Where {$_.ResourceType -eq "Room"} | Set-CalendarProcessing -BookingWindowInDays 365

Happy Booking!

•  Add a user as a full permission to the room mailbox via PowerShell:

  Assign Permission Add-MailboxPermission -Identity “[email protected]” -User “[email protected]” -AccessRights Fullaccess -InheritanceType All

• Open room mailbox with OWA
• Login to user who have the full permission of room mailbox by using OWA.
• Click on “your alias” at top right corner and select room mailbox
• When the OWA open room mailbox, we can click on “calendar” -> Share -> “Share this calendar”  and select the share permission. Then, we can select the person and send the announcement email.

On the Client Side the user will be able to the see the only if they have permissions. If no permissions are assigned it will give a warning saying it is unable to connect. This will go away once the permissions are set right!

1. Open OWA (Outlook Web apps) by opening http://mail.office365.com
2. Calendar – > My Calendars  -> open “other Calendars” ,then input the alias of the Room-mailbox

Microsoft Article: Create A New Room Mailbox