Prevent double bookings of resources in Exchange 2007 and 2010

Exchange 2007

This is easily done with powershell. Use the following syntax to set AllowConflicts to $false:

Set-MailboxCalendarSettings -Identity <mailbox identity> -AllowConflicts:$false

If you want to set this on all room mailboxes in one command use the following:

Get-Mailbox | where {$_.ResourceType -eq “Room” } | Set-MailboxCalendarSettings -AllowConflicts:$false

To check that this actually worked you can use the following command:

Get-MailboxCalendarSettings -Identity <mailbox identity> | fl

Confirm that AllowConflicts is set to $false.

Exchange 2010

In Exchange 2010 the MailboxCalendarSettings har been removed and you should use Set-CalendarProcessing instead:

Set-CalendarProcessing -Identity <mailbox identity> -AllowConflicts:$false

If you want to set this on all room mailboxes in one command use the following:

Get-Mailbox | where {$_.ResourceType -eq “Room” } | Set-CalendarProcessing -AllowConflicts:$false

And to make sure that it worked:

Get-CalendarProcessing -Identity <mailbox identity> | fl

7 Responses to Prevent double bookings of resources in Exchange 2007 and 2010

  1. Shannon Pace says:

    sorry to drag up an old thread…

    we have just done this on some room resources, but once the command has been run in powershell, how long should it take before conflicts are detected?

    i have run the command but am still able to book meeting requests at the same time as existing entries.

    any help would be much appreciated.



    • msundis says:

      Hi Shannon, thanks for reading and don’t be sorry, I’m happy to help!

      Depending on your environment there can be a delay up to 10 minuters before the settings has changed. I hope it works for you now or else there might be something else causing the delay.

  2. cnbarnes says:

    Shannon isn’t the only one that is having this problem. :-(

    I used the command mentioned above, but it still allows conflicting reservations. Well… sort of. When I create the first reservation, I get a “Your Request was Accepted”. If another person attempts to reserve the item for a conflicting time, their reservation appears on the item’s calendar (but if you open it, you see “there is a conflict”), and they never receive a confirmation NOR a rejection.

    This might be helpful:
    [PS] C:\Windows\system32>Get-CalendarProcessing -Identity mifi1540 | fl

    RunspaceId : e3378599-4343-43a3-98d9-fa32b087c988
    AutomateProcessing : AutoAccept
    AllowConflicts : False
    BookingWindowInDays : 365
    MaximumDurationInMinutes : 0
    AllowRecurringMeetings : True
    EnforceSchedulingHorizon : True
    ScheduleOnlyDuringWorkHours : False
    ConflictPercentageAllowed : 0
    MaximumConflictInstances : 0
    ForwardRequestsToDelegates : True
    DeleteAttachments : True
    DeleteComments : True
    RemovePrivateProperty : True
    DeleteSubject : True
    AddOrganizerToSubject : True
    DeleteNonCalendarItems : True
    TentativePendingApproval : False
    EnableResponseDetails : True
    OrganizerInfo : True
    ResourceDelegates : {domainname/OU/Staff/User}
    RequestOutOfPolicy :
    AllRequestOutOfPolicy : False
    BookInPolicy :
    AllBookInPolicy : True
    RequestInPolicy :
    AllRequestInPolicy : False
    AddAdditionalResponse : False
    AdditionalResponse :
    RemoveOldMeetingMessages : True
    AddNewRequestsTentatively : False
    ProcessExternalMeetingMessages : False
    RemoveForwardedMeetingNotifications : False
    Identity : domainmane/OU/Mifi Card 1540

  3. Emman says:

    I have the same problem. Any solution to this please?

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  5. Greggers says:

    I had an identical issue for this, in my case it was a recurring appointment blocked out every day for a week for the entire day, yet when people sent meeting requests and the resource booking attendant was accepting them it allowed the double bookings. I found that the creator of the recurring appointment showed the time as being Free, instead of Busy, which allowed the double booking. I was able to reproduce, and when creating a new recurring appointment with Time as busy, meetings were denied.

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