Option Explicit
Dim SubFolder As MAPIFolder

Sub ChangeFolderClassAllSubFolders()
    Dim i               As Long
    Dim iNameSpace      As NameSpace
    Dim myOlApp         As Outlook.Application
    Dim ChosenFolder    As Object
    Dim Folders         As New Collection
    Dim EntryID         As New Collection
    Dim StoreID         As New Collection
       
    Set myOlApp = Outlook.Application
    Set iNameSpace = myOlApp.GetNamespace("MAPI")
    Set ChosenFolder = iNameSpace.PickFolder
    If ChosenFolder Is Nothing Then
GoTo ExitSub:
    End If

    Call GetFolder(Folders, EntryID, StoreID, ChosenFolder)
        ChangeFolderContainer
        
    For i = 1 To Folders.Count
        Set SubFolder = myOlApp.Session.GetFolderFromID(EntryID(i), StoreID(i))
        On Error Resume Next
        ChangeFolderContainer
    
        On Error GoTo 0
    Next i     
ExitSub:      
End Sub
    
  
Private Sub ChangeFolderContainer()
Dim oFolder As Outlook.folder
Dim oPA As Outlook.PropertyAccessor
Dim PropName, Value, folderType As String

PropName = "http://schemas.microsoft.com/mapi/proptag/0x3613001E"
Value = "IPF.Note"

On Error Resume Next
Set oFolder = SubFolder 'Application.ActiveExplorer.CurrentFolder
Set oPA = oFolder.PropertyAccessor

folderType = oPA.GetProperty(PropName)
Debug.Print SubFolder.Name & " " & (folderType)

If folderType = "IPF.Imap" Then

oPA.SetProperty PropName, Value
Debug.Print "     Changed: " & SubFolder.Name & " " & Value

End If

Set oFolder = Nothing
Set oPA = Nothing
End Sub
     
    
Sub GetFolder(Folders As Collection, EntryID As Collection, StoreID As Collection, Fld As MAPIFolder)
    Dim SubFolder       As MAPIFolder
       
    Folders.Add Fld.FolderPath
    EntryID.Add Fld.EntryID
    StoreID.Add Fld.StoreID
    For Each SubFolder In Fld.Folders
        GetFolder Folders, EntryID, StoreID, SubFolder
    Next SubFolder
       
ExitSub:
    Set SubFolder = Nothing
       
End Sub