Imports System
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports System.io
Imports System.Threading
 
Public Class Form1
    Inherits System.Windows.Forms.Form
    Public stream As NetworkStream
    Public sr As StreamReader
 
    Private Sub cmdPOPen_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles cmdPOPen.Click
        Dim server As String = "mein server"
        Dim user As String = "\Domäne\meine Emailadresse"
        Dim password As String = "mein PW"
        Dim message As String
        Dim send As String
        Dim client As New TcpClient(server, 110)
        stream = client.GetStream()
        sr = New StreamReader(stream)
        txtResponse.Text += sendCommand("?")
        txtResponse.Text += sendCommand("USER " + user)
        txtResponse.Text += sendCommand("PASS " + password)
        txtResponse.Text += sendCommand("STAT" + vbCrLf)
        txtResponse.Text += sendCommand("RETR 1" + vbCrLf) 
        txtResponse.Text += sendCommand("QUIT" + vbCrLf)
    End Sub
    Private Function sendCommand(ByVal send As String) As String
        send += vbCrLf
        Dim data As [Byte]() = Encoding.ASCII.GetBytes(send)
        stream.Write(data, 0, data.Length)
        sr = New StreamReader(stream)
        Dim buffer As New StringBuilder
        Do While sr.Peek() > 0
            Thread.Sleep(100)
            buffer.Append(sr.ReadLine + vbCrLf)
        Loop
        Return buffer.ToString
    End Function
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
 
    End Sub
End Class