Public Sub FindFiles()
 
   Dim outfiles As New List(Of String)
 
   For Each file As String In IO.Directory.EnumerateFiles("....", "....")
 
      'Dateiinhalt lesen (Zeilen)
      Dim lines() As String = IO.File.ReadAllLines(file)
 
      Dim names As New Dictionary(Of String, Integer)
      Dim tox As Boolean = False
      Dim st, en As Integer, name As String
 
      'Datei-inhalt durchsuchen
      For i As Integer = 0 To lines.Length - 1
         'Anschriftenblock startet?
         If lines(i).StartsWith("To: ") Then tox = True
 
         If tox Then
            st = lines(i).IndexOf("<")
            If st >= 0 Then
               en = lines(i).IndexOf(">", st)
               If en >= 0 Then
                  'Empfänger-Name gefunden / registrieren
                  name = lines(i).Substring(st + 1, en - st - 1)
 
                  If names.ContainsKey(name) Then
                     names(name) = names(name) + 1
                  Else
                     names.Add(name, 1)
                  End If
               End If
            End If
         End If
      Next i
 
      If names.Count > 25 Then outfiles.Add(file)
   Next file
 
   If outfiles.Count > 0 Then
      IO.File.WriteAllLines _
         ("....", outfiles.ToArray)
   End If
 
End Sub