Error when accessing a resource mailbox: “The value ” is already present in the collection”

When accessing a resource mailbox in Exchange 2013 EAC, you may encounter an error that you prevents you from viewing or editing the room mailbox properties:

Capture

 

Powershell is no good either!

 

Get-CalendarProcessing <Room>
WARNING: An unexpected error has occurred and a Watson dump is being generated: The value ” is already present in the
collection.
The value ” is already present in the collection.
    + CategoryInfo          : NotSpecified: (:) [Get-CalendarProcessing], InvalidOperationException
    + FullyQualifiedErrorId : System.InvalidOperationException,Microsoft.Exchange.Management.StoreTasks.GetCalendarProcessing

 

Cause: Typically this is because there is a disabled mailbox listed in the RequestInPolicy or BookInPolicy attributes for the room.

Solution: Run the following in Exchange Powershell to clear the values. Example:  Set-CalendarProcessing <Room> -BookInPolicy $null  

Once done, you should be able to access the room via Powershell or EAC and re-add any required requesters to the room policy. Alternatively, if you have Exchange 2010 still around, you can simply remove the disabled mailbox via the 2010 EMC.

 

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