Error: value ” is already present in the Collection while accessing a resource mailbox in Exchange 2013 EAC.

Scenario:

Environment: Exchange 2013

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

 

Unable to modify resource mailbox settings . error: value " is already present in collection

Get-CalendarProcessing <Room>

Below watson error logged while performing the change using EMS

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: RequestInPolicy or BookInPolicy attributes for the room have incorrect values

 

Resolution:

1.Set-CalendarProcessing <Room> -BookInPolicy $null  

check if the above command works, if it fails proceed to step 2

2.  Take backup of resource Mailbox Configuration and export the resource mailbox content as PST before making changes to the Mailbox using MFCMAPI.

3. Using MFCMAPI, logon to the resource mailbox , find Top of Information Store -> Calendar -> Open Accosiated Contents Table , select the item with subject "IPM.Configuration.Calendar", double click to open "PR_ROAMING_DICTIONARY", delete element related RequestOutOfPolicy/BookInPolicy/RequestInPolicy, and click OKset the value for above fields to null ""