Public Class Form1
 
    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) _
      Handles Button1.Click
 
        Dim N1 As String = "..."
        Dim N2 As String = "..."
 
        Dim olApp As Object
        Dim oItem As Object
 
        olApp = CreateObject("Outlook.Application")
        oItem = olApp.CreateItem(0)
        Dim BodySignature As String
        With oItem
            .To = "..."
            .CC = ""
            .BCC = ""
            .Subject = ""
            BodySignature = .Body.ToString '= hier geschieht der Fehler
            .Body = N1 & N2 & vbNewLine & vbNewLine & BodySignature
            .Attachments.Add()
            .Send()
        End With
    End Sub
End Class