Mit diesem Makro können Sie den Betreff einer Email ändern, ohne diese öffnen zu müssen.
Public Sub EditSubject()
  Dim obj As Object
  Dim Sel As Outlook.Selection
  Dim DoSave As Boolean
  Dim NewSubject As String
  
  If TypeOf Application.ActiveWindow Is Outlook.Inspector Then
    Set obj = Application.ActiveInspector.CurrentItem
  Else
    Set Sel = Application.ActiveExplorer.Selection
    If Sel.Count Then
      Set obj = Sel(1)
      DoSave = True
    End If
  End If
  If Not obj Is Nothing Then
    NewSubject = InputBox("Neuer Betreff:", , obj.Subject)
    If NewSubject <> "" Then
      obj.Subject = NewSubject
      If DoSave Then
        obj.Save
      End If
    End If
  End If
End Sub