Visual Basic.NET - Enviar correo gmail

Imports System.Net.Mail

Public Class frmCorreo

    Private Sub btnEnvia_Click(sender As Object, e As EventArgs) Handles btnEnvia.Click

        Dim message As New MailMessage

        Dim smtp As New SmtpClient

        With message

            .From = New System.Net.Mail.MailAddress(txtDe.Text)

            .To.Add(txtPara.Text)

            .Body = txtMessage.Text

            .Subject = txtAsunto.Text

            .Priority = System.Net.Mail.MailPriority.Normal

        End With

        With smtp

            .EnableSsl = True

            .Port = "587"

            .Host = "smtp.gmail.com"

            .Credentials = New Net.NetworkCredential(txtDe.Text, txtPassword.Text)

            .Send(message)

        End With

        Try

            MessageBox.Show("Su mensaje de correo ha sido enviado.", "Correo enviado",

                             MessageBoxButtons.OK)

        Catch ex As Exception

            MessageBox.Show("Error: " & ex.Message, "Error al enviar correo",

                             MessageBoxButtons.OK)

        End Try

    End Sub

End Class

https://myaccount.google.com/lesssecureapps?pli=1

Sub EnviarReportesEmail()

    Dim smtp As New System.Net.Mail.SmtpClient

    Dim mensaje As New MailMessage(New MailAddress("alli.reportes@gmail.com"), New MailAddress(frmSETTING.txtClaveEmailCliente.Text))

    'Dim mensaje As New MailMessage(New MailAddress("alli.reportes@gmail.com"), New MailAddress("lenin-linares@hotmail.com"))

    '--------------------------------------------------------------------------------------------------------------------------------

    If My.Computer.FileSystem.FileExists("C:\REPORTES\Facturas.PDF") = False Then

        'MsgBox("El archivo NO existe!!")

        Exit Sub

    Else

        'MsgBox("El archivo existe!!")

    End If

    '---------------------------------------------------------------------------------------------------------------------------------

    If My.Computer.Network.IsAvailable() Then

        Try

            If My.Computer.Network.Ping("google.com", 3000) Then

                'MsgBox("Conectado.")

                smtp.Host = "smtp.gmail.com"

                smtp.Port = 587

                smtp.EnableSsl = True

                smtp.UseDefaultCredentials = False

                smtp.Credentials = New System.Net.NetworkCredential("reportes@gmail.com", "alli123456")

                '-------------------------------------------------------------------

                mensaje.Subject = "Reporte del negocio: " & Today.ToString

                'MsgBox(mensaje.Subject)

                mensaje.IsBodyHtml = False 'envia el mensaje como html

                mensaje.Attachments.Add(New Attachment("C:\REPORTES\Facturas.PDF"))

                mensaje.Priority = MailPriority.Normal

                '===============================================

                Try

                    smtp.Send(mensaje)

                Catch ex As Exception

                    MsgBox("Error en My.Computer.Network.Ping")

                End Try

            Else

                'MsgBox("Error de conexión.")

                'MsgBox("PRUEBA ENVIO REPORTE")

                tmrEnviaReporteAuto2.Enabled = True

            End If

        Catch ex As PingException

            'MsgBox("Error de conexión.")

        End Try

    Else

        'MsgBox("No conectado")

    End If

    '******************************************************************

    tmrEnviaReporteAuto.Enabled = False

End Sub