Danke für die Hilfestellung, hat soweit gut funktioniert:
# Abrufen des Namespaces
Add-Type -assembly "Microsoft.Office.Interop.Outlook"
$outlook = New-Object -ComObject Outlook.Application
$namespace = $outlook.GetNamespace('MAPI')
#--------------
# Default Contacts folder
$Contacts = $namespace.GetDefaultFolder(10)
$KundenContacts = $Contacts.Folders["Kunden"]
$LieferantenContacts = $Contacts.Folders["Lieferanten"]
$Kunden_cnt = 0
$Lieferanten_cnt = 0
<#
#------------------------------
# Schleife für Subfolder Kunden
foreach ($Contact in $KundenContacts.Items)
{
if($Contact.Body -and $Contact.Categories -like "*Kundenstamm*" )
{
Write-Output ("--" + $Contact.Categories+ " :" + $Contact.FullName + " ........" + $Contact.Body )