How GetResponseCode in live.com and hotmail - vb.net

Question

I want to send a message to the hotmail mail and test the mail whether it exists or not. If it does not exist, a message appears for me. A code was made and tested on the gmail mail and it works great, but when converting it to hotmail it did not work. Please help
Private Function GetResponseCode(ByVal ResponseString As String) As Integer
Try
Return Integer.Parse(ResponseString.Substring(0, 3))
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Function
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
For i = 0 To ListBox1.Items.Count - 1
Dim tClient As TcpClient = New TcpClient("smtp-mail.outlook.com", 587)
Dim CRLF As String = vbCrLf
Dim dataBuffer As Byte()
Dim ResponseString As String
Dim netStream As NetworkStream = tClient.GetStream()
Dim reader As StreamReader = New StreamReader(netStream)
ResponseString = reader.ReadLine()
dataBuffer = BytesFromString("HELO" & CRLF)
netStream.Write(dataBuffer, 0, dataBuffer.Length)
ResponseString = reader.ReadLine()
dataBuffer = BytesFromString("MAIL FROM:<fx121#gmail.com>" & CRLF)
netStream.Write(dataBuffer, 0, dataBuffer.Length)
ResponseString = reader.ReadLine()
dataBuffer = BytesFromString("RCPT TO:<" & Itm(i) + "#hotmail.com" & ">" & CRLF)
netStream.Write(dataBuffer, 0, dataBuffer.Length)
ResponseString = reader.ReadLine()
If GetResponseCode(ResponseString) = 550 Then
MsgBox("Not exist")
Else
MsgBox("exist")
End If
dataBuffer = BytesFromString("QUITE" & CRLF)
netStream.Write(dataBuffer, 0, dataBuffer.Length)
tClient.Close()
Next
End Sub