Visual Basic.NET - envio de correo por codigo vb.net

Imports System.Net.Mail

Imports System.Text

Public Class Form1

    Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim Mail As MailMessage = Nothing

        Dim smtp As SmtpClient = Nothing

        Dim Expedidor As String = "qwerty@gmail.com"

        Dim Destinatorio As String = "xyz@yahoo.fr"

        Try

            Mail = New System.Net.Mail.MailMessage

            Mail.SubjectEncoding = UTF8Encoding.UTF8

            Mail.BodyEncoding = UTF8Encoding.UTF8

            Mail.Subject = "Prueba Smtp GMail"

            Mail.Body = "Mensaje prueba Smtp GMail " & Now()

            Mail.From = New MailAddress(Expedidor)

            Mail.To.Add(New MailAddress(Destinatorio))

            smtp = New SmtpClient()

            smtp.Host = "smtp.gmail.com"

            smtp.Port = 25

            smtp.EnableSsl = False

            smtp.Credentials = New System.Net.NetworkCredential("qwerty@gmail.com", "ptlpipnutlbakxyx") ' contraseña de aplicación dado por Google

            Try

                smtp.Send(Mail)

            Catch ex As Exception

                MessageBox.Show(ex.Message)

            End Try

            Mail.Attachments.Clear()

            Mail.Attachments.Dispose()

            Mail.Dispose()

        Catch ex As ApplicationException

            MessageBox.Show(ex.Message)

        Finally

            smtp = Nothing

            Try

                Mail.Dispose()

            Catch

            End Try

            Mail = Nothing

        End Try

    End Sub

End Class

' ...

           smtp = New SmtpClient()

            smtp.Host = "smtp.gmail.com"

            smtp.Port = 567

            smtp.EnableSsl = True

            smtp.Credentials = New System.Net.NetworkCredential("qwerty@gmail.com", "ptlpipnutlbakxyx") ' contraseña de aplicación dado por Google

' ...