Exchange Kalendereinträge anpassen via powershell

<#
   Vor dem Start des Skript ist dem User welcher das Skript später ausführt die Impersonation-Berechtigungzu erteilen:
   In diesem Beispiel der User 'Administrator' (Bitte einmalig in einer EMS ausführen)  

    New-ManagementRoleAssignment -Name:impersonationAssignmentName -Role:ApplicationImpersonation -User:Administrator
#>

# Start Variablen -------------------------------------------------------------------------
# FQDN des Exchange
$exserver = "ex.domain.tld"  
# Name des Raum-/Gerätepostfachs
$mailbox = "Raumpostfach@domain.tld"  

# Ende Variablen -------------------------------------------------------------------------

if ($PSVersionTable.PSVersion.Major -lt 3){write-host "ERROR: Minimum Powershell Version 3.0 is required!" -F Yellow; return}    

# Active Directory Modul laden
Import-Module ActiveDirectory

# EWS DLL laden
Add-Type -Path "$PSScriptRoot\Microsoft.Exchange.WebServices.dll"  

# Allen Zertifikaten vertrauen
Add-Type @"  
    using System.Net;
    using System.Security.Cryptography.X509Certificates;
    public class TrustAllCertsPolicy : ICertificatePolicy {
        public bool CheckValidationResult(
            ServicePoint srvPoint, X509Certificate certificate,
            WebRequest request, int certificateProblem) {
            return true;
        }
    }
"@  
# Trust all certs policy dem ServicePointManager zuweisen
[System.Net.ServicePointManager]::CertificatePolicy = New-Object TrustAllCertsPolicy

# EWS Objekt erstellen
$ews = new-object Microsoft.Exchange.WebServices.Data.ExchangeService([Microsoft.Exchange.WebServices.Data.ExchangeVersion]::Exchange2013)
$ews.Url = "https://$exserver/ews/exchange.asmx"  
# Benutze die Credentials mit dem das Skript ausgeführt wird
$ews.UseDefaultCredentials = $true
$ews.ImpersonatedUserId = New-Object Microsoft.Exchange.WebServices.Data.ImpersonatedUserId([Microsoft.Exchange.WebServices.Data.ConnectingIdType]::SmtpAddress, [string]$mailbox)


# -----------------------------
$view = New-Object Microsoft.Exchange.WebServices.Data.ItemView(10000)
$view.PropertySet = New-Object Microsoft.Exchange.WebServices.Data.PropertySet([Microsoft.Exchange.WebServices.Data.BasePropertySet]::FirstClassProperties)
$result = $ews.FindItems([Microsoft.Exchange.WebServices.Data.WellKnownFolderName]::Calendar,$view)
$result.Items | ?{$_.LegacyFreeBusyStatus -eq [Microsoft.Exchange.WebServices.Data.LegacyFreeBusyStatus]::Free} | %{
    $_.LegacyFreeBusyStatus = [Microsoft.Exchange.WebServices.Data.LegacyFreeBusyStatus]::Busy
    $_.Update([Microsoft.Exchange.WebServices.Data.ConflictResolutionMode]::AutoResolve)
}

[void][reflection.assembly]::LoadWithPartialName("microsoft.visualbasic")  
$objOL = [microsoft.visualbasic.interaction]::GetObject($null,"Outlook.Application")  
if (!$objOL){$objOL = New-Object -Com Outlook.Application}
$objOL.ActiveExplorer().CurrentFolder.Items | ?{$_.BusyStatus -eq 0} | %{$_.BusyStatus = 2; $_.Save()}